[linux-2.6-microblaze.git] / arch / x86 / kvm / mmu / mmu.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * Kernel-based Virtual Machine driver for Linux
 *
 * This module enables machines with Intel VT-x extensions to run virtual
 * machines without emulation or binary translation.
 *
 * MMU support
 *
 * Copyright (C) 2006 Qumranet, Inc.
 * Copyright 2010 Red Hat, Inc. and/or its affiliates.
 *
 * Authors:
 *   Yaniv Kamay  <yaniv@qumranet.com>
 *   Avi Kivity   <avi@qumranet.com>
 */

#include "irq.h"
#include "ioapic.h"
#include "mmu.h"
#include "mmu_internal.h"
#include "tdp_mmu.h"
#include "x86.h"
#include "kvm_cache_regs.h"
#include "smm.h"
#include "kvm_emulate.h"
#include "cpuid.h"
#include "spte.h"

#include <linux/kvm_host.h>
#include <linux/types.h>
#include <linux/string.h>
#include <linux/mm.h>
#include <linux/highmem.h>
#include <linux/moduleparam.h>
#include <linux/export.h>
#include <linux/swap.h>
#include <linux/hugetlb.h>
#include <linux/compiler.h>
#include <linux/srcu.h>
#include <linux/slab.h>
#include <linux/sched/signal.h>
#include <linux/uaccess.h>
#include <linux/hash.h>
#include <linux/kern_levels.h>
#include <linux/kthread.h>

#include <asm/page.h>
#include <asm/memtype.h>
#include <asm/cmpxchg.h>
#include <asm/io.h>
#include <asm/set_memory.h>
#include <asm/vmx.h>
#include <asm/kvm_page_track.h>
#include "trace.h"

extern bool itlb_multihit_kvm_mitigation;

int __read_mostly nx_huge_pages = -1;
static uint __read_mostly nx_huge_pages_recovery_period_ms;
#ifdef CONFIG_PREEMPT_RT
/* Recovery can cause latency spikes, disable it for PREEMPT_RT.  */
static uint __read_mostly nx_huge_pages_recovery_ratio = 0;
#else
static uint __read_mostly nx_huge_pages_recovery_ratio = 60;
#endif

static int set_nx_huge_pages(const char *val, const struct kernel_param *kp);
static int set_nx_huge_pages_recovery_param(const char *val, const struct kernel_param *kp);

static const struct kernel_param_ops nx_huge_pages_ops = {
        .set = set_nx_huge_pages,
        .get = param_get_bool,
};

static const struct kernel_param_ops nx_huge_pages_recovery_param_ops = {
        .set = set_nx_huge_pages_recovery_param,
        .get = param_get_uint,
};

module_param_cb(nx_huge_pages, &nx_huge_pages_ops, &nx_huge_pages, 0644);
__MODULE_PARM_TYPE(nx_huge_pages, "bool");
module_param_cb(nx_huge_pages_recovery_ratio, &nx_huge_pages_recovery_param_ops,
                &nx_huge_pages_recovery_ratio, 0644);
__MODULE_PARM_TYPE(nx_huge_pages_recovery_ratio, "uint");
module_param_cb(nx_huge_pages_recovery_period_ms, &nx_huge_pages_recovery_param_ops,
                &nx_huge_pages_recovery_period_ms, 0644);
__MODULE_PARM_TYPE(nx_huge_pages_recovery_period_ms, "uint");

static bool __read_mostly force_flush_and_sync_on_reuse;
module_param_named(flush_on_reuse, force_flush_and_sync_on_reuse, bool, 0644);

/*
 * When setting this variable to true it enables Two-Dimensional-Paging
 * where the hardware walks 2 page tables:
 * 1. the guest-virtual to guest-physical
 * 2. while doing 1. it walks guest-physical to host-physical
 * If the hardware supports that we don't need to do shadow paging.
 */
bool tdp_enabled = false;

bool __ro_after_init tdp_mmu_allowed;

#ifdef CONFIG_X86_64
bool __read_mostly tdp_mmu_enabled = true;
module_param_named(tdp_mmu, tdp_mmu_enabled, bool, 0444);
#endif

static int max_huge_page_level __read_mostly;
static int tdp_root_level __read_mostly;
static int max_tdp_level __read_mostly;

#ifdef MMU_DEBUG
bool dbg = 0;
module_param(dbg, bool, 0644);
#endif

#define PTE_PREFETCH_NUM                8

#include <trace/events/kvm.h>

/* make pte_list_desc fit well in cache lines */
#define PTE_LIST_EXT 14

/*
 * Slight optimization of cacheline layout, by putting `more' and `spte_count'
 * at the start; then accessing it will only use one single cacheline for
 * either full (entries==PTE_LIST_EXT) case or entries<=6.
 */
struct pte_list_desc {
        struct pte_list_desc *more;
        /*
         * Stores number of entries stored in the pte_list_desc.  No need to be
         * u64 but just for easier alignment.  When PTE_LIST_EXT, means full.
         */
        u64 spte_count;
        u64 *sptes[PTE_LIST_EXT];
};

struct kvm_shadow_walk_iterator {
        u64 addr;
        hpa_t shadow_addr;
        u64 *sptep;
        int level;
        unsigned index;
};

#define for_each_shadow_entry_using_root(_vcpu, _root, _addr, _walker)     \
        for (shadow_walk_init_using_root(&(_walker), (_vcpu),              \
                                         (_root), (_addr));                \
             shadow_walk_okay(&(_walker));                                 \
             shadow_walk_next(&(_walker)))

#define for_each_shadow_entry(_vcpu, _addr, _walker)            \
        for (shadow_walk_init(&(_walker), _vcpu, _addr);        \
             shadow_walk_okay(&(_walker));                      \
             shadow_walk_next(&(_walker)))

#define for_each_shadow_entry_lockless(_vcpu, _addr, _walker, spte)     \
        for (shadow_walk_init(&(_walker), _vcpu, _addr);                \
             shadow_walk_okay(&(_walker)) &&                            \
                ({ spte = mmu_spte_get_lockless(_walker.sptep); 1; });  \
             __shadow_walk_next(&(_walker), spte))

static struct kmem_cache *pte_list_desc_cache;
struct kmem_cache *mmu_page_header_cache;
static struct percpu_counter kvm_total_used_mmu_pages;

static void mmu_spte_set(u64 *sptep, u64 spte);

struct kvm_mmu_role_regs {
        const unsigned long cr0;
        const unsigned long cr4;
        const u64 efer;
};

#define CREATE_TRACE_POINTS
#include "mmutrace.h"

/*
 * Yes, lot's of underscores.  They're a hint that you probably shouldn't be
 * reading from the role_regs.  Once the root_role is constructed, it becomes
 * the single source of truth for the MMU's state.
 */
#define BUILD_MMU_ROLE_REGS_ACCESSOR(reg, name, flag)                   \
static inline bool __maybe_unused                                       \
____is_##reg##_##name(const struct kvm_mmu_role_regs *regs)             \
{                                                                       \
        return !!(regs->reg & flag);                                    \
}
BUILD_MMU_ROLE_REGS_ACCESSOR(cr0, pg, X86_CR0_PG);
BUILD_MMU_ROLE_REGS_ACCESSOR(cr0, wp, X86_CR0_WP);
BUILD_MMU_ROLE_REGS_ACCESSOR(cr4, pse, X86_CR4_PSE);
BUILD_MMU_ROLE_REGS_ACCESSOR(cr4, pae, X86_CR4_PAE);
BUILD_MMU_ROLE_REGS_ACCESSOR(cr4, smep, X86_CR4_SMEP);
BUILD_MMU_ROLE_REGS_ACCESSOR(cr4, smap, X86_CR4_SMAP);
BUILD_MMU_ROLE_REGS_ACCESSOR(cr4, pke, X86_CR4_PKE);
BUILD_MMU_ROLE_REGS_ACCESSOR(cr4, la57, X86_CR4_LA57);
BUILD_MMU_ROLE_REGS_ACCESSOR(efer, nx, EFER_NX);
BUILD_MMU_ROLE_REGS_ACCESSOR(efer, lma, EFER_LMA);

/*
 * The MMU itself (with a valid role) is the single source of truth for the
 * MMU.  Do not use the regs used to build the MMU/role, nor the vCPU.  The
 * regs don't account for dependencies, e.g. clearing CR4 bits if CR0.PG=1,
 * and the vCPU may be incorrect/irrelevant.
 */
#define BUILD_MMU_ROLE_ACCESSOR(base_or_ext, reg, name)         \
static inline bool __maybe_unused is_##reg##_##name(struct kvm_mmu *mmu)        \
{                                                               \
        return !!(mmu->cpu_role. base_or_ext . reg##_##name);   \
}
BUILD_MMU_ROLE_ACCESSOR(base, cr0, wp);
BUILD_MMU_ROLE_ACCESSOR(ext,  cr4, pse);
BUILD_MMU_ROLE_ACCESSOR(ext,  cr4, smep);
BUILD_MMU_ROLE_ACCESSOR(ext,  cr4, smap);
BUILD_MMU_ROLE_ACCESSOR(ext,  cr4, pke);
BUILD_MMU_ROLE_ACCESSOR(ext,  cr4, la57);
BUILD_MMU_ROLE_ACCESSOR(base, efer, nx);
BUILD_MMU_ROLE_ACCESSOR(ext,  efer, lma);

static inline bool is_cr0_pg(struct kvm_mmu *mmu)
{
        return mmu->cpu_role.base.level > 0;
}

static inline bool is_cr4_pae(struct kvm_mmu *mmu)
{
        return !mmu->cpu_role.base.has_4_byte_gpte;
}

static struct kvm_mmu_role_regs vcpu_to_role_regs(struct kvm_vcpu *vcpu)
{
        struct kvm_mmu_role_regs regs = {
                .cr0 = kvm_read_cr0_bits(vcpu, KVM_MMU_CR0_ROLE_BITS),
                .cr4 = kvm_read_cr4_bits(vcpu, KVM_MMU_CR4_ROLE_BITS),
                .efer = vcpu->arch.efer,
        };

        return regs;
}

static inline bool kvm_available_flush_tlb_with_range(void)
{
        return kvm_x86_ops.tlb_remote_flush_with_range;
}

static void kvm_flush_remote_tlbs_with_range(struct kvm *kvm,
                struct kvm_tlb_range *range)
{
        int ret = -ENOTSUPP;

        if (range && kvm_x86_ops.tlb_remote_flush_with_range)
                ret = static_call(kvm_x86_tlb_remote_flush_with_range)(kvm, range);

        if (ret)
                kvm_flush_remote_tlbs(kvm);
}

void kvm_flush_remote_tlbs_with_address(struct kvm *kvm,
                u64 start_gfn, u64 pages)
{
        struct kvm_tlb_range range;

        range.start_gfn = start_gfn;
        range.pages = pages;

        kvm_flush_remote_tlbs_with_range(kvm, &range);
}

static void mark_mmio_spte(struct kvm_vcpu *vcpu, u64 *sptep, u64 gfn,
                           unsigned int access)
{
        u64 spte = make_mmio_spte(vcpu, gfn, access);

        trace_mark_mmio_spte(sptep, gfn, spte);
        mmu_spte_set(sptep, spte);
}

static gfn_t get_mmio_spte_gfn(u64 spte)
{
        u64 gpa = spte & shadow_nonpresent_or_rsvd_lower_gfn_mask;

        gpa |= (spte >> SHADOW_NONPRESENT_OR_RSVD_MASK_LEN)
               & shadow_nonpresent_or_rsvd_mask;

        return gpa >> PAGE_SHIFT;
}

static unsigned get_mmio_spte_access(u64 spte)
{
        return spte & shadow_mmio_access_mask;
}

static bool check_mmio_spte(struct kvm_vcpu *vcpu, u64 spte)
{
        u64 kvm_gen, spte_gen, gen;

        gen = kvm_vcpu_memslots(vcpu)->generation;
        if (unlikely(gen & KVM_MEMSLOT_GEN_UPDATE_IN_PROGRESS))
                return false;

        kvm_gen = gen & MMIO_SPTE_GEN_MASK;
        spte_gen = get_mmio_spte_generation(spte);

        trace_check_mmio_spte(spte, kvm_gen, spte_gen);
        return likely(kvm_gen == spte_gen);
}

static int is_cpuid_PSE36(void)
{
        return 1;
}

#ifdef CONFIG_X86_64
static void __set_spte(u64 *sptep, u64 spte)
{
        WRITE_ONCE(*sptep, spte);
}

static void __update_clear_spte_fast(u64 *sptep, u64 spte)
{
        WRITE_ONCE(*sptep, spte);
}

static u64 __update_clear_spte_slow(u64 *sptep, u64 spte)
{
        return xchg(sptep, spte);
}

static u64 __get_spte_lockless(u64 *sptep)
{
        return READ_ONCE(*sptep);
}
#else
union split_spte {
        struct {
                u32 spte_low;
                u32 spte_high;
        };
        u64 spte;
};

static void count_spte_clear(u64 *sptep, u64 spte)
{
        struct kvm_mmu_page *sp =  sptep_to_sp(sptep);

        if (is_shadow_present_pte(spte))
                return;

        /* Ensure the spte is completely set before we increase the count */
        smp_wmb();
        sp->clear_spte_count++;
}

static void __set_spte(u64 *sptep, u64 spte)
{
        union split_spte *ssptep, sspte;

        ssptep = (union split_spte *)sptep;
        sspte = (union split_spte)spte;

        ssptep->spte_high = sspte.spte_high;

        /*
         * If we map the spte from nonpresent to present, We should store
         * the high bits firstly, then set present bit, so cpu can not
         * fetch this spte while we are setting the spte.
         */
        smp_wmb();

        WRITE_ONCE(ssptep->spte_low, sspte.spte_low);
}

static void __update_clear_spte_fast(u64 *sptep, u64 spte)
{
        union split_spte *ssptep, sspte;

        ssptep = (union split_spte *)sptep;
        sspte = (union split_spte)spte;

        WRITE_ONCE(ssptep->spte_low, sspte.spte_low);

        /*
         * If we map the spte from present to nonpresent, we should clear
         * present bit firstly to avoid vcpu fetch the old high bits.
         */
        smp_wmb();

        ssptep->spte_high = sspte.spte_high;
        count_spte_clear(sptep, spte);
}

static u64 __update_clear_spte_slow(u64 *sptep, u64 spte)
{
        union split_spte *ssptep, sspte, orig;

        ssptep = (union split_spte *)sptep;
        sspte = (union split_spte)spte;

        /* xchg acts as a barrier before the setting of the high bits */
        orig.spte_low = xchg(&ssptep->spte_low, sspte.spte_low);
        orig.spte_high = ssptep->spte_high;
        ssptep->spte_high = sspte.spte_high;
        count_spte_clear(sptep, spte);

        return orig.spte;
}

/*
 * The idea using the light way get the spte on x86_32 guest is from
 * gup_get_pte (mm/gup.c).
 *
 * An spte tlb flush may be pending, because kvm_set_pte_rmap
 * coalesces them and we are running out of the MMU lock.  Therefore
 * we need to protect against in-progress updates of the spte.
 *
 * Reading the spte while an update is in progress may get the old value
 * for the high part of the spte.  The race is fine for a present->non-present
 * change (because the high part of the spte is ignored for non-present spte),
 * but for a present->present change we must reread the spte.
 *
 * All such changes are done in two steps (present->non-present and
 * non-present->present), hence it is enough to count the number of
 * present->non-present updates: if it changed while reading the spte,
 * we might have hit the race.  This is done using clear_spte_count.
 */
static u64 __get_spte_lockless(u64 *sptep)
{
        struct kvm_mmu_page *sp =  sptep_to_sp(sptep);
        union split_spte spte, *orig = (union split_spte *)sptep;
        int count;

retry:
        count = sp->clear_spte_count;
        smp_rmb();

        spte.spte_low = orig->spte_low;
        smp_rmb();

        spte.spte_high = orig->spte_high;
        smp_rmb();

        if (unlikely(spte.spte_low != orig->spte_low ||
              count != sp->clear_spte_count))
                goto retry;

        return spte.spte;
}
#endif

/* Rules for using mmu_spte_set:
 * Set the sptep from nonpresent to present.
 * Note: the sptep being assigned *must* be either not present
 * or in a state where the hardware will not attempt to update
 * the spte.
 */
static void mmu_spte_set(u64 *sptep, u64 new_spte)
{
        WARN_ON(is_shadow_present_pte(*sptep));
        __set_spte(sptep, new_spte);
}

/*
 * Update the SPTE (excluding the PFN), but do not track changes in its
 * accessed/dirty status.
 */
static u64 mmu_spte_update_no_track(u64 *sptep, u64 new_spte)
{
        u64 old_spte = *sptep;

        WARN_ON(!is_shadow_present_pte(new_spte));
        check_spte_writable_invariants(new_spte);

        if (!is_shadow_present_pte(old_spte)) {
                mmu_spte_set(sptep, new_spte);
                return old_spte;
        }

        if (!spte_has_volatile_bits(old_spte))
                __update_clear_spte_fast(sptep, new_spte);
        else
                old_spte = __update_clear_spte_slow(sptep, new_spte);

        WARN_ON(spte_to_pfn(old_spte) != spte_to_pfn(new_spte));

        return old_spte;
}

/* Rules for using mmu_spte_update:
 * Update the state bits, it means the mapped pfn is not changed.
 *
 * Whenever an MMU-writable SPTE is overwritten with a read-only SPTE, remote
 * TLBs must be flushed. Otherwise rmap_write_protect will find a read-only
 * spte, even though the writable spte might be cached on a CPU's TLB.
 *
 * Returns true if the TLB needs to be flushed
 */
static bool mmu_spte_update(u64 *sptep, u64 new_spte)
{
        bool flush = false;
        u64 old_spte = mmu_spte_update_no_track(sptep, new_spte);

        if (!is_shadow_present_pte(old_spte))
                return false;

        /*
         * For the spte updated out of mmu-lock is safe, since
         * we always atomically update it, see the comments in
         * spte_has_volatile_bits().
         */
        if (is_mmu_writable_spte(old_spte) &&
              !is_writable_pte(new_spte))
                flush = true;

        /*
         * Flush TLB when accessed/dirty states are changed in the page tables,
         * to guarantee consistency between TLB and page tables.
         */

        if (is_accessed_spte(old_spte) && !is_accessed_spte(new_spte)) {
                flush = true;
                kvm_set_pfn_accessed(spte_to_pfn(old_spte));
        }

        if (is_dirty_spte(old_spte) && !is_dirty_spte(new_spte)) {
                flush = true;
                kvm_set_pfn_dirty(spte_to_pfn(old_spte));
        }

        return flush;
}

/*
 * Rules for using mmu_spte_clear_track_bits:
 * It sets the sptep from present to nonpresent, and track the
 * state bits, it is used to clear the last level sptep.
 * Returns the old PTE.
 */
static u64 mmu_spte_clear_track_bits(struct kvm *kvm, u64 *sptep)
{
        kvm_pfn_t pfn;
        u64 old_spte = *sptep;
        int level = sptep_to_sp(sptep)->role.level;
        struct page *page;

        if (!is_shadow_present_pte(old_spte) ||
            !spte_has_volatile_bits(old_spte))
                __update_clear_spte_fast(sptep, 0ull);
        else
                old_spte = __update_clear_spte_slow(sptep, 0ull);

        if (!is_shadow_present_pte(old_spte))
                return old_spte;

        kvm_update_page_stats(kvm, level, -1);

        pfn = spte_to_pfn(old_spte);

        /*
         * KVM doesn't hold a reference to any pages mapped into the guest, and
         * instead uses the mmu_notifier to ensure that KVM unmaps any pages
         * before they are reclaimed.  Sanity check that, if the pfn is backed
         * by a refcounted page, the refcount is elevated.
         */
        page = kvm_pfn_to_refcounted_page(pfn);
        WARN_ON(page && !page_count(page));

        if (is_accessed_spte(old_spte))
                kvm_set_pfn_accessed(pfn);

        if (is_dirty_spte(old_spte))
                kvm_set_pfn_dirty(pfn);

        return old_spte;
}

/*
 * Rules for using mmu_spte_clear_no_track:
 * Directly clear spte without caring the state bits of sptep,
 * it is used to set the upper level spte.
 */
static void mmu_spte_clear_no_track(u64 *sptep)
{
        __update_clear_spte_fast(sptep, 0ull);
}

static u64 mmu_spte_get_lockless(u64 *sptep)
{
        return __get_spte_lockless(sptep);
}

/* Returns the Accessed status of the PTE and resets it at the same time. */
static bool mmu_spte_age(u64 *sptep)
{
        u64 spte = mmu_spte_get_lockless(sptep);

        if (!is_accessed_spte(spte))
                return false;

        if (spte_ad_enabled(spte)) {
                clear_bit((ffs(shadow_accessed_mask) - 1),
                          (unsigned long *)sptep);
        } else {
                /*
                 * Capture the dirty status of the page, so that it doesn't get
                 * lost when the SPTE is marked for access tracking.
                 */
                if (is_writable_pte(spte))
                        kvm_set_pfn_dirty(spte_to_pfn(spte));

                spte = mark_spte_for_access_track(spte);
                mmu_spte_update_no_track(sptep, spte);
        }

        return true;
}

static inline bool is_tdp_mmu_active(struct kvm_vcpu *vcpu)
{
        return tdp_mmu_enabled && vcpu->arch.mmu->root_role.direct;
}

static void walk_shadow_page_lockless_begin(struct kvm_vcpu *vcpu)
{
        if (is_tdp_mmu_active(vcpu)) {
                kvm_tdp_mmu_walk_lockless_begin();
        } else {
                /*
                 * Prevent page table teardown by making any free-er wait during
                 * kvm_flush_remote_tlbs() IPI to all active vcpus.
                 */
                local_irq_disable();

                /*
                 * Make sure a following spte read is not reordered ahead of the write
                 * to vcpu->mode.
                 */
                smp_store_mb(vcpu->mode, READING_SHADOW_PAGE_TABLES);
        }
}

static void walk_shadow_page_lockless_end(struct kvm_vcpu *vcpu)
{
        if (is_tdp_mmu_active(vcpu)) {
                kvm_tdp_mmu_walk_lockless_end();
        } else {
                /*
                 * Make sure the write to vcpu->mode is not reordered in front of
                 * reads to sptes.  If it does, kvm_mmu_commit_zap_page() can see us
                 * OUTSIDE_GUEST_MODE and proceed to free the shadow page table.
                 */
                smp_store_release(&vcpu->mode, OUTSIDE_GUEST_MODE);
                local_irq_enable();
        }
}

static int mmu_topup_memory_caches(struct kvm_vcpu *vcpu, bool maybe_indirect)
{
        int r;

        /* 1 rmap, 1 parent PTE per level, and the prefetched rmaps. */
        r = kvm_mmu_topup_memory_cache(&vcpu->arch.mmu_pte_list_desc_cache,
                                       1 + PT64_ROOT_MAX_LEVEL + PTE_PREFETCH_NUM);
        if (r)
                return r;
        r = kvm_mmu_topup_memory_cache(&vcpu->arch.mmu_shadow_page_cache,
                                       PT64_ROOT_MAX_LEVEL);
        if (r)
                return r;
        if (maybe_indirect) {
                r = kvm_mmu_topup_memory_cache(&vcpu->arch.mmu_shadowed_info_cache,
                                               PT64_ROOT_MAX_LEVEL);
                if (r)
                        return r;
        }
        return kvm_mmu_topup_memory_cache(&vcpu->arch.mmu_page_header_cache,
                                          PT64_ROOT_MAX_LEVEL);
}

static void mmu_free_memory_caches(struct kvm_vcpu *vcpu)
{
        kvm_mmu_free_memory_cache(&vcpu->arch.mmu_pte_list_desc_cache);
        kvm_mmu_free_memory_cache(&vcpu->arch.mmu_shadow_page_cache);
        kvm_mmu_free_memory_cache(&vcpu->arch.mmu_shadowed_info_cache);
        kvm_mmu_free_memory_cache(&vcpu->arch.mmu_page_header_cache);
}

static void mmu_free_pte_list_desc(struct pte_list_desc *pte_list_desc)
{
        kmem_cache_free(pte_list_desc_cache, pte_list_desc);
}

static bool sp_has_gptes(struct kvm_mmu_page *sp);

static gfn_t kvm_mmu_page_get_gfn(struct kvm_mmu_page *sp, int index)
{
        if (sp->role.passthrough)
                return sp->gfn;

        if (!sp->role.direct)
                return sp->shadowed_translation[index] >> PAGE_SHIFT;

        return sp->gfn + (index << ((sp->role.level - 1) * SPTE_LEVEL_BITS));
}

/*
 * For leaf SPTEs, fetch the *guest* access permissions being shadowed. Note
 * that the SPTE itself may have a more constrained access permissions that
 * what the guest enforces. For example, a guest may create an executable
 * huge PTE but KVM may disallow execution to mitigate iTLB multihit.
 */
static u32 kvm_mmu_page_get_access(struct kvm_mmu_page *sp, int index)
{
        if (sp_has_gptes(sp))
                return sp->shadowed_translation[index] & ACC_ALL;

        /*
         * For direct MMUs (e.g. TDP or non-paging guests) or passthrough SPs,
         * KVM is not shadowing any guest page tables, so the "guest access
         * permissions" are just ACC_ALL.
         *
         * For direct SPs in indirect MMUs (shadow paging), i.e. when KVM
         * is shadowing a guest huge page with small pages, the guest access
         * permissions being shadowed are the access permissions of the huge
         * page.
         *
         * In both cases, sp->role.access contains the correct access bits.
         */
        return sp->role.access;
}

static void kvm_mmu_page_set_translation(struct kvm_mmu_page *sp, int index,
                                         gfn_t gfn, unsigned int access)
{
        if (sp_has_gptes(sp)) {
                sp->shadowed_translation[index] = (gfn << PAGE_SHIFT) | access;
                return;
        }

        WARN_ONCE(access != kvm_mmu_page_get_access(sp, index),
                  "access mismatch under %s page %llx (expected %u, got %u)\n",
                  sp->role.passthrough ? "passthrough" : "direct",
                  sp->gfn, kvm_mmu_page_get_access(sp, index), access);

        WARN_ONCE(gfn != kvm_mmu_page_get_gfn(sp, index),
                  "gfn mismatch under %s page %llx (expected %llx, got %llx)\n",
                  sp->role.passthrough ? "passthrough" : "direct",
                  sp->gfn, kvm_mmu_page_get_gfn(sp, index), gfn);
}

static void kvm_mmu_page_set_access(struct kvm_mmu_page *sp, int index,
                                    unsigned int access)
{
        gfn_t gfn = kvm_mmu_page_get_gfn(sp, index);

        kvm_mmu_page_set_translation(sp, index, gfn, access);
}

/*
 * Return the pointer to the large page information for a given gfn,
 * handling slots that are not large page aligned.
 */
static struct kvm_lpage_info *lpage_info_slot(gfn_t gfn,
                const struct kvm_memory_slot *slot, int level)
{
        unsigned long idx;

        idx = gfn_to_index(gfn, slot->base_gfn, level);
        return &slot->arch.lpage_info[level - 2][idx];
}

static void update_gfn_disallow_lpage_count(const struct kvm_memory_slot *slot,
                                            gfn_t gfn, int count)
{
        struct kvm_lpage_info *linfo;
        int i;

        for (i = PG_LEVEL_2M; i <= KVM_MAX_HUGEPAGE_LEVEL; ++i) {
                linfo = lpage_info_slot(gfn, slot, i);
                linfo->disallow_lpage += count;
                WARN_ON(linfo->disallow_lpage < 0);
        }
}

void kvm_mmu_gfn_disallow_lpage(const struct kvm_memory_slot *slot, gfn_t gfn)
{
        update_gfn_disallow_lpage_count(slot, gfn, 1);
}

void kvm_mmu_gfn_allow_lpage(const struct kvm_memory_slot *slot, gfn_t gfn)
{
        update_gfn_disallow_lpage_count(slot, gfn, -1);
}

static void account_shadowed(struct kvm *kvm, struct kvm_mmu_page *sp)
{
        struct kvm_memslots *slots;
        struct kvm_memory_slot *slot;
        gfn_t gfn;

        kvm->arch.indirect_shadow_pages++;
        gfn = sp->gfn;
        slots = kvm_memslots_for_spte_role(kvm, sp->role);
        slot = __gfn_to_memslot(slots, gfn);

        /* the non-leaf shadow pages are keeping readonly. */
        if (sp->role.level > PG_LEVEL_4K)
                return kvm_slot_page_track_add_page(kvm, slot, gfn,
                                                    KVM_PAGE_TRACK_WRITE);

        kvm_mmu_gfn_disallow_lpage(slot, gfn);

        if (kvm_mmu_slot_gfn_write_protect(kvm, slot, gfn, PG_LEVEL_4K))
                kvm_flush_remote_tlbs_with_address(kvm, gfn, 1);
}

void track_possible_nx_huge_page(struct kvm *kvm, struct kvm_mmu_page *sp)
{
        /*
         * If it's possible to replace the shadow page with an NX huge page,
         * i.e. if the shadow page is the only thing currently preventing KVM
         * from using a huge page, add the shadow page to the list of "to be
         * zapped for NX recovery" pages.  Note, the shadow page can already be
         * on the list if KVM is reusing an existing shadow page, i.e. if KVM
         * links a shadow page at multiple points.
         */
        if (!list_empty(&sp->possible_nx_huge_page_link))
                return;

        ++kvm->stat.nx_lpage_splits;
        list_add_tail(&sp->possible_nx_huge_page_link,
                      &kvm->arch.possible_nx_huge_pages);
}

static void account_nx_huge_page(struct kvm *kvm, struct kvm_mmu_page *sp,
                                 bool nx_huge_page_possible)
{
        sp->nx_huge_page_disallowed = true;

        if (nx_huge_page_possible)
                track_possible_nx_huge_page(kvm, sp);
}

static void unaccount_shadowed(struct kvm *kvm, struct kvm_mmu_page *sp)
{
        struct kvm_memslots *slots;
        struct kvm_memory_slot *slot;
        gfn_t gfn;

        kvm->arch.indirect_shadow_pages--;
        gfn = sp->gfn;
        slots = kvm_memslots_for_spte_role(kvm, sp->role);
        slot = __gfn_to_memslot(slots, gfn);
        if (sp->role.level > PG_LEVEL_4K)
                return kvm_slot_page_track_remove_page(kvm, slot, gfn,
                                                       KVM_PAGE_TRACK_WRITE);

        kvm_mmu_gfn_allow_lpage(slot, gfn);
}

void untrack_possible_nx_huge_page(struct kvm *kvm, struct kvm_mmu_page *sp)
{
        if (list_empty(&sp->possible_nx_huge_page_link))
                return;

        --kvm->stat.nx_lpage_splits;
        list_del_init(&sp->possible_nx_huge_page_link);
}

static void unaccount_nx_huge_page(struct kvm *kvm, struct kvm_mmu_page *sp)
{
        sp->nx_huge_page_disallowed = false;

        untrack_possible_nx_huge_page(kvm, sp);
}

static struct kvm_memory_slot *
gfn_to_memslot_dirty_bitmap(struct kvm_vcpu *vcpu, gfn_t gfn,
                            bool no_dirty_log)
{
        struct kvm_memory_slot *slot;

        slot = kvm_vcpu_gfn_to_memslot(vcpu, gfn);
        if (!slot || slot->flags & KVM_MEMSLOT_INVALID)
                return NULL;
        if (no_dirty_log && kvm_slot_dirty_track_enabled(slot))
                return NULL;

        return slot;
}

/*
 * About rmap_head encoding:
 *
 * If the bit zero of rmap_head->val is clear, then it points to the only spte
 * in this rmap chain. Otherwise, (rmap_head->val & ~1) points to a struct
 * pte_list_desc containing more mappings.
 */

/*
 * Returns the number of pointers in the rmap chain, not counting the new one.
 */
static int pte_list_add(struct kvm_mmu_memory_cache *cache, u64 *spte,
                        struct kvm_rmap_head *rmap_head)
{
        struct pte_list_desc *desc;
        int count = 0;

        if (!rmap_head->val) {
                rmap_printk("%p %llx 0->1\n", spte, *spte);
                rmap_head->val = (unsigned long)spte;
        } else if (!(rmap_head->val & 1)) {
                rmap_printk("%p %llx 1->many\n", spte, *spte);
                desc = kvm_mmu_memory_cache_alloc(cache);
                desc->sptes[0] = (u64 *)rmap_head->val;
                desc->sptes[1] = spte;
                desc->spte_count = 2;
                rmap_head->val = (unsigned long)desc | 1;
                ++count;
        } else {
                rmap_printk("%p %llx many->many\n", spte, *spte);
                desc = (struct pte_list_desc *)(rmap_head->val & ~1ul);
                while (desc->spte_count == PTE_LIST_EXT) {
                        count += PTE_LIST_EXT;
                        if (!desc->more) {
                                desc->more = kvm_mmu_memory_cache_alloc(cache);
                                desc = desc->more;
                                desc->spte_count = 0;
                                break;
                        }
                        desc = desc->more;
                }
                count += desc->spte_count;
                desc->sptes[desc->spte_count++] = spte;
        }
        return count;
}

static void
pte_list_desc_remove_entry(struct kvm_rmap_head *rmap_head,
                           struct pte_list_desc *desc, int i,
                           struct pte_list_desc *prev_desc)
{
        int j = desc->spte_count - 1;

        desc->sptes[i] = desc->sptes[j];
        desc->sptes[j] = NULL;
        desc->spte_count--;
        if (desc->spte_count)
                return;
        if (!prev_desc && !desc->more)
                rmap_head->val = 0;
        else
                if (prev_desc)
                        prev_desc->more = desc->more;
                else
                        rmap_head->val = (unsigned long)desc->more | 1;
        mmu_free_pte_list_desc(desc);
}

static void pte_list_remove(u64 *spte, struct kvm_rmap_head *rmap_head)
{
        struct pte_list_desc *desc;
        struct pte_list_desc *prev_desc;
        int i;

        if (!rmap_head->val) {
                pr_err("%s: %p 0->BUG\n", __func__, spte);
                BUG();
        } else if (!(rmap_head->val & 1)) {
                rmap_printk("%p 1->0\n", spte);
                if ((u64 *)rmap_head->val != spte) {
                        pr_err("%s:  %p 1->BUG\n", __func__, spte);
                        BUG();
                }
                rmap_head->val = 0;
        } else {
                rmap_printk("%p many->many\n", spte);
                desc = (struct pte_list_desc *)(rmap_head->val & ~1ul);
                prev_desc = NULL;
                while (desc) {
                        for (i = 0; i < desc->spte_count; ++i) {
                                if (desc->sptes[i] == spte) {
                                        pte_list_desc_remove_entry(rmap_head,
                                                        desc, i, prev_desc);
                                        return;
                                }
                        }
                        prev_desc = desc;
                        desc = desc->more;
                }
                pr_err("%s: %p many->many\n", __func__, spte);
                BUG();
        }
}

static void kvm_zap_one_rmap_spte(struct kvm *kvm,
                                  struct kvm_rmap_head *rmap_head, u64 *sptep)
{
        mmu_spte_clear_track_bits(kvm, sptep);
        pte_list_remove(sptep, rmap_head);
}

/* Return true if at least one SPTE was zapped, false otherwise */
static bool kvm_zap_all_rmap_sptes(struct kvm *kvm,
                                   struct kvm_rmap_head *rmap_head)
{
        struct pte_list_desc *desc, *next;
        int i;

        if (!rmap_head->val)
                return false;

        if (!(rmap_head->val & 1)) {
                mmu_spte_clear_track_bits(kvm, (u64 *)rmap_head->val);
                goto out;
        }

        desc = (struct pte_list_desc *)(rmap_head->val & ~1ul);

        for (; desc; desc = next) {
                for (i = 0; i < desc->spte_count; i++)
                        mmu_spte_clear_track_bits(kvm, desc->sptes[i]);
                next = desc->more;
                mmu_free_pte_list_desc(desc);
        }
out:
        /* rmap_head is meaningless now, remember to reset it */
        rmap_head->val = 0;
        return true;
}

unsigned int pte_list_count(struct kvm_rmap_head *rmap_head)
{
        struct pte_list_desc *desc;
        unsigned int count = 0;

        if (!rmap_head->val)
                return 0;
        else if (!(rmap_head->val & 1))
                return 1;

        desc = (struct pte_list_desc *)(rmap_head->val & ~1ul);

        while (desc) {
                count += desc->spte_count;
                desc = desc->more;
        }

        return count;
}

static struct kvm_rmap_head *gfn_to_rmap(gfn_t gfn, int level,
                                         const struct kvm_memory_slot *slot)
{
        unsigned long idx;

        idx = gfn_to_index(gfn, slot->base_gfn, level);
        return &slot->arch.rmap[level - PG_LEVEL_4K][idx];
}

static bool rmap_can_add(struct kvm_vcpu *vcpu)
{
        struct kvm_mmu_memory_cache *mc;

        mc = &vcpu->arch.mmu_pte_list_desc_cache;
        return kvm_mmu_memory_cache_nr_free_objects(mc);
}

static void rmap_remove(struct kvm *kvm, u64 *spte)
{
        struct kvm_memslots *slots;
        struct kvm_memory_slot *slot;
        struct kvm_mmu_page *sp;
        gfn_t gfn;
        struct kvm_rmap_head *rmap_head;

        sp = sptep_to_sp(spte);
        gfn = kvm_mmu_page_get_gfn(sp, spte_index(spte));

        /*
         * Unlike rmap_add, rmap_remove does not run in the context of a vCPU
         * so we have to determine which memslots to use based on context
         * information in sp->role.
         */
        slots = kvm_memslots_for_spte_role(kvm, sp->role);

        slot = __gfn_to_memslot(slots, gfn);
        rmap_head = gfn_to_rmap(gfn, sp->role.level, slot);

        pte_list_remove(spte, rmap_head);
}

/*
 * Used by the following functions to iterate through the sptes linked by a
 * rmap.  All fields are private and not assumed to be used outside.
 */
struct rmap_iterator {
        /* private fields */
        struct pte_list_desc *desc;     /* holds the sptep if not NULL */
        int pos;                        /* index of the sptep */
};

/*
 * Iteration must be started by this function.  This should also be used after
 * removing/dropping sptes from the rmap link because in such cases the
 * information in the iterator may not be valid.
 *
 * Returns sptep if found, NULL otherwise.
 */
static u64 *rmap_get_first(struct kvm_rmap_head *rmap_head,
                           struct rmap_iterator *iter)
{
        u64 *sptep;

        if (!rmap_head->val)
                return NULL;

        if (!(rmap_head->val & 1)) {
                iter->desc = NULL;
                sptep = (u64 *)rmap_head->val;
                goto out;
        }

        iter->desc = (struct pte_list_desc *)(rmap_head->val & ~1ul);
        iter->pos = 0;
        sptep = iter->desc->sptes[iter->pos];
out:
        BUG_ON(!is_shadow_present_pte(*sptep));
        return sptep;
}

/*
 * Must be used with a valid iterator: e.g. after rmap_get_first().
 *
 * Returns sptep if found, NULL otherwise.
 */
static u64 *rmap_get_next(struct rmap_iterator *iter)
{
        u64 *sptep;

        if (iter->desc) {
                if (iter->pos < PTE_LIST_EXT - 1) {
                        ++iter->pos;
                        sptep = iter->desc->sptes[iter->pos];
                        if (sptep)
                                goto out;
                }

                iter->desc = iter->desc->more;

                if (iter->desc) {
                        iter->pos = 0;
                        /* desc->sptes[0] cannot be NULL */
                        sptep = iter->desc->sptes[iter->pos];
                        goto out;
                }
        }

        return NULL;
out:
        BUG_ON(!is_shadow_present_pte(*sptep));
        return sptep;
}

#define for_each_rmap_spte(_rmap_head_, _iter_, _spte_)                 \
        for (_spte_ = rmap_get_first(_rmap_head_, _iter_);              \
             _spte_; _spte_ = rmap_get_next(_iter_))

static void drop_spte(struct kvm *kvm, u64 *sptep)
{
        u64 old_spte = mmu_spte_clear_track_bits(kvm, sptep);

        if (is_shadow_present_pte(old_spte))
                rmap_remove(kvm, sptep);
}

static void drop_large_spte(struct kvm *kvm, u64 *sptep, bool flush)
{
        struct kvm_mmu_page *sp;

        sp = sptep_to_sp(sptep);
        WARN_ON(sp->role.level == PG_LEVEL_4K);

        drop_spte(kvm, sptep);

        if (flush)
                kvm_flush_remote_tlbs_with_address(kvm, sp->gfn,
                        KVM_PAGES_PER_HPAGE(sp->role.level));
}

/*
 * Write-protect on the specified @sptep, @pt_protect indicates whether
 * spte write-protection is caused by protecting shadow page table.
 *
 * Note: write protection is difference between dirty logging and spte
 * protection:
 * - for dirty logging, the spte can be set to writable at anytime if
 *   its dirty bitmap is properly set.
 * - for spte protection, the spte can be writable only after unsync-ing
 *   shadow page.
 *
 * Return true if tlb need be flushed.
 */
static bool spte_write_protect(u64 *sptep, bool pt_protect)
{
        u64 spte = *sptep;

        if (!is_writable_pte(spte) &&
            !(pt_protect && is_mmu_writable_spte(spte)))
                return false;

        rmap_printk("spte %p %llx\n", sptep, *sptep);

        if (pt_protect)
                spte &= ~shadow_mmu_writable_mask;
        spte = spte & ~PT_WRITABLE_MASK;

        return mmu_spte_update(sptep, spte);
}

static bool rmap_write_protect(struct kvm_rmap_head *rmap_head,
                               bool pt_protect)
{
        u64 *sptep;
        struct rmap_iterator iter;
        bool flush = false;

        for_each_rmap_spte(rmap_head, &iter, sptep)
                flush |= spte_write_protect(sptep, pt_protect);

        return flush;
}

static bool spte_clear_dirty(u64 *sptep)
{
        u64 spte = *sptep;

        rmap_printk("spte %p %llx\n", sptep, *sptep);

        MMU_WARN_ON(!spte_ad_enabled(spte));
        spte &= ~shadow_dirty_mask;
        return mmu_spte_update(sptep, spte);
}

static bool spte_wrprot_for_clear_dirty(u64 *sptep)
{
        bool was_writable = test_and_clear_bit(PT_WRITABLE_SHIFT,
                                               (unsigned long *)sptep);
        if (was_writable && !spte_ad_enabled(*sptep))
                kvm_set_pfn_dirty(spte_to_pfn(*sptep));

        return was_writable;
}

/*
 * Gets the GFN ready for another round of dirty logging by clearing the
 *      - D bit on ad-enabled SPTEs, and
 *      - W bit on ad-disabled SPTEs.
 * Returns true iff any D or W bits were cleared.
 */
static bool __rmap_clear_dirty(struct kvm *kvm, struct kvm_rmap_head *rmap_head,
                               const struct kvm_memory_slot *slot)
{
        u64 *sptep;
        struct rmap_iterator iter;
        bool flush = false;

        for_each_rmap_spte(rmap_head, &iter, sptep)
                if (spte_ad_need_write_protect(*sptep))
                        flush |= spte_wrprot_for_clear_dirty(sptep);
                else
                        flush |= spte_clear_dirty(sptep);

        return flush;
}

/**
 * kvm_mmu_write_protect_pt_masked - write protect selected PT level pages
 * @kvm: kvm instance
 * @slot: slot to protect
 * @gfn_offset: start of the BITS_PER_LONG pages we care about
 * @mask: indicates which pages we should protect
 *
 * Used when we do not need to care about huge page mappings.
 */
static void kvm_mmu_write_protect_pt_masked(struct kvm *kvm,
                                     struct kvm_memory_slot *slot,
                                     gfn_t gfn_offset, unsigned long mask)
{
        struct kvm_rmap_head *rmap_head;

        if (tdp_mmu_enabled)
                kvm_tdp_mmu_clear_dirty_pt_masked(kvm, slot,
                                slot->base_gfn + gfn_offset, mask, true);

        if (!kvm_memslots_have_rmaps(kvm))
                return;

        while (mask) {
                rmap_head = gfn_to_rmap(slot->base_gfn + gfn_offset + __ffs(mask),
                                        PG_LEVEL_4K, slot);
                rmap_write_protect(rmap_head, false);

                /* clear the first set bit */
                mask &= mask - 1;
        }
}

/**
 * kvm_mmu_clear_dirty_pt_masked - clear MMU D-bit for PT level pages, or write
 * protect the page if the D-bit isn't supported.
 * @kvm: kvm instance
 * @slot: slot to clear D-bit
 * @gfn_offset: start of the BITS_PER_LONG pages we care about
 * @mask: indicates which pages we should clear D-bit
 *
 * Used for PML to re-log the dirty GPAs after userspace querying dirty_bitmap.
 */
static void kvm_mmu_clear_dirty_pt_masked(struct kvm *kvm,
                                         struct kvm_memory_slot *slot,
                                         gfn_t gfn_offset, unsigned long mask)
{
        struct kvm_rmap_head *rmap_head;

        if (tdp_mmu_enabled)
                kvm_tdp_mmu_clear_dirty_pt_masked(kvm, slot,
                                slot->base_gfn + gfn_offset, mask, false);

        if (!kvm_memslots_have_rmaps(kvm))
                return;

        while (mask) {
                rmap_head = gfn_to_rmap(slot->base_gfn + gfn_offset + __ffs(mask),
                                        PG_LEVEL_4K, slot);
                __rmap_clear_dirty(kvm, rmap_head, slot);

                /* clear the first set bit */
                mask &= mask - 1;
        }
}

/**
 * kvm_arch_mmu_enable_log_dirty_pt_masked - enable dirty logging for selected
 * PT level pages.
 *
 * It calls kvm_mmu_write_protect_pt_masked to write protect selected pages to
 * enable dirty logging for them.
 *
 * We need to care about huge page mappings: e.g. during dirty logging we may
 * have such mappings.
 */
void kvm_arch_mmu_enable_log_dirty_pt_masked(struct kvm *kvm,
                                struct kvm_memory_slot *slot,
                                gfn_t gfn_offset, unsigned long mask)
{
        /*
         * Huge pages are NOT write protected when we start dirty logging in
         * initially-all-set mode; must write protect them here so that they
         * are split to 4K on the first write.
         *
         * The gfn_offset is guaranteed to be aligned to 64, but the base_gfn
         * of memslot has no such restriction, so the range can cross two large
         * pages.
         */
        if (kvm_dirty_log_manual_protect_and_init_set(kvm)) {
                gfn_t start = slot->base_gfn + gfn_offset + __ffs(mask);
                gfn_t end = slot->base_gfn + gfn_offset + __fls(mask);

                if (READ_ONCE(eager_page_split))
                        kvm_mmu_try_split_huge_pages(kvm, slot, start, end, PG_LEVEL_4K);

                kvm_mmu_slot_gfn_write_protect(kvm, slot, start, PG_LEVEL_2M);

                /* Cross two large pages? */
                if (ALIGN(start << PAGE_SHIFT, PMD_SIZE) !=
                    ALIGN(end << PAGE_SHIFT, PMD_SIZE))
                        kvm_mmu_slot_gfn_write_protect(kvm, slot, end,
                                                       PG_LEVEL_2M);
        }

        /* Now handle 4K PTEs.  */
        if (kvm_x86_ops.cpu_dirty_log_size)
                kvm_mmu_clear_dirty_pt_masked(kvm, slot, gfn_offset, mask);
        else
                kvm_mmu_write_protect_pt_masked(kvm, slot, gfn_offset, mask);
}

int kvm_cpu_dirty_log_size(void)
{
        return kvm_x86_ops.cpu_dirty_log_size;
}

bool kvm_mmu_slot_gfn_write_protect(struct kvm *kvm,
                                    struct kvm_memory_slot *slot, u64 gfn,
                                    int min_level)
{
        struct kvm_rmap_head *rmap_head;
        int i;
        bool write_protected = false;

        if (kvm_memslots_have_rmaps(kvm)) {
                for (i = min_level; i <= KVM_MAX_HUGEPAGE_LEVEL; ++i) {
                        rmap_head = gfn_to_rmap(gfn, i, slot);
                        write_protected |= rmap_write_protect(rmap_head, true);
                }
        }

        if (tdp_mmu_enabled)
                write_protected |=
                        kvm_tdp_mmu_write_protect_gfn(kvm, slot, gfn, min_level);

        return write_protected;
}

static bool kvm_vcpu_write_protect_gfn(struct kvm_vcpu *vcpu, u64 gfn)
{
        struct kvm_memory_slot *slot;

        slot = kvm_vcpu_gfn_to_memslot(vcpu, gfn);
        return kvm_mmu_slot_gfn_write_protect(vcpu->kvm, slot, gfn, PG_LEVEL_4K);
}

static bool __kvm_zap_rmap(struct kvm *kvm, struct kvm_rmap_head *rmap_head,
                           const struct kvm_memory_slot *slot)
{
        return kvm_zap_all_rmap_sptes(kvm, rmap_head);
}

static bool kvm_zap_rmap(struct kvm *kvm, struct kvm_rmap_head *rmap_head,
                         struct kvm_memory_slot *slot, gfn_t gfn, int level,
                         pte_t unused)
{
        return __kvm_zap_rmap(kvm, rmap_head, slot);
}

static bool kvm_set_pte_rmap(struct kvm *kvm, struct kvm_rmap_head *rmap_head,
                             struct kvm_memory_slot *slot, gfn_t gfn, int level,
                             pte_t pte)
{
        u64 *sptep;
        struct rmap_iterator iter;
        bool need_flush = false;
        u64 new_spte;
        kvm_pfn_t new_pfn;

        WARN_ON(pte_huge(pte));
        new_pfn = pte_pfn(pte);

restart:
        for_each_rmap_spte(rmap_head, &iter, sptep) {
                rmap_printk("spte %p %llx gfn %llx (%d)\n",
                            sptep, *sptep, gfn, level);

                need_flush = true;

                if (pte_write(pte)) {
                        kvm_zap_one_rmap_spte(kvm, rmap_head, sptep);
                        goto restart;
                } else {
                        new_spte = kvm_mmu_changed_pte_notifier_make_spte(
                                        *sptep, new_pfn);

                        mmu_spte_clear_track_bits(kvm, sptep);
                        mmu_spte_set(sptep, new_spte);
                }
        }

        if (need_flush && kvm_available_flush_tlb_with_range()) {
                kvm_flush_remote_tlbs_with_address(kvm, gfn, 1);
                return false;
        }

        return need_flush;
}

struct slot_rmap_walk_iterator {
        /* input fields. */
        const struct kvm_memory_slot *slot;
        gfn_t start_gfn;
        gfn_t end_gfn;
        int start_level;
        int end_level;

        /* output fields. */
        gfn_t gfn;
        struct kvm_rmap_head *rmap;
        int level;

        /* private field. */
        struct kvm_rmap_head *end_rmap;
};

static void
rmap_walk_init_level(struct slot_rmap_walk_iterator *iterator, int level)
{
        iterator->level = level;
        iterator->gfn = iterator->start_gfn;
        iterator->rmap = gfn_to_rmap(iterator->gfn, level, iterator->slot);
        iterator->end_rmap = gfn_to_rmap(iterator->end_gfn, level, iterator->slot);
}

static void
slot_rmap_walk_init(struct slot_rmap_walk_iterator *iterator,
                    const struct kvm_memory_slot *slot, int start_level,
                    int end_level, gfn_t start_gfn, gfn_t end_gfn)
{
        iterator->slot = slot;
        iterator->start_level = start_level;
        iterator->end_level = end_level;
        iterator->start_gfn = start_gfn;
        iterator->end_gfn = end_gfn;

        rmap_walk_init_level(iterator, iterator->start_level);
}

static bool slot_rmap_walk_okay(struct slot_rmap_walk_iterator *iterator)
{
        return !!iterator->rmap;
}

static void slot_rmap_walk_next(struct slot_rmap_walk_iterator *iterator)
{
        while (++iterator->rmap <= iterator->end_rmap) {
                iterator->gfn += (1UL << KVM_HPAGE_GFN_SHIFT(iterator->level));

                if (iterator->rmap->val)
                        return;
        }

        if (++iterator->level > iterator->end_level) {
                iterator->rmap = NULL;
                return;
        }

        rmap_walk_init_level(iterator, iterator->level);
}

#define for_each_slot_rmap_range(_slot_, _start_level_, _end_level_,    \
           _start_gfn, _end_gfn, _iter_)                                \
        for (slot_rmap_walk_init(_iter_, _slot_, _start_level_,         \
                                 _end_level_, _start_gfn, _end_gfn);    \
             slot_rmap_walk_okay(_iter_);                               \
             slot_rmap_walk_next(_iter_))

typedef bool (*rmap_handler_t)(struct kvm *kvm, struct kvm_rmap_head *rmap_head,
                               struct kvm_memory_slot *slot, gfn_t gfn,
                               int level, pte_t pte);

static __always_inline bool kvm_handle_gfn_range(struct kvm *kvm,
                                                 struct kvm_gfn_range *range,
                                                 rmap_handler_t handler)
{
        struct slot_rmap_walk_iterator iterator;
        bool ret = false;

        for_each_slot_rmap_range(range->slot, PG_LEVEL_4K, KVM_MAX_HUGEPAGE_LEVEL,
                                 range->start, range->end - 1, &iterator)
                ret |= handler(kvm, iterator.rmap, range->slot, iterator.gfn,
                               iterator.level, range->pte);

        return ret;
}

bool kvm_unmap_gfn_range(struct kvm *kvm, struct kvm_gfn_range *range)
{
        bool flush = false;

        if (kvm_memslots_have_rmaps(kvm))
                flush = kvm_handle_gfn_range(kvm, range, kvm_zap_rmap);

        if (tdp_mmu_enabled)
                flush = kvm_tdp_mmu_unmap_gfn_range(kvm, range, flush);

        return flush;
}

bool kvm_set_spte_gfn(struct kvm *kvm, struct kvm_gfn_range *range)
{
        bool flush = false;

        if (kvm_memslots_have_rmaps(kvm))
                flush = kvm_handle_gfn_range(kvm, range, kvm_set_pte_rmap);

        if (tdp_mmu_enabled)
                flush |= kvm_tdp_mmu_set_spte_gfn(kvm, range);

        return flush;
}

static bool kvm_age_rmap(struct kvm *kvm, struct kvm_rmap_head *rmap_head,
                         struct kvm_memory_slot *slot, gfn_t gfn, int level,
                         pte_t unused)
{
        u64 *sptep;
        struct rmap_iterator iter;
        int young = 0;

        for_each_rmap_spte(rmap_head, &iter, sptep)
                young |= mmu_spte_age(sptep);

        return young;
}

static bool kvm_test_age_rmap(struct kvm *kvm, struct kvm_rmap_head *rmap_head,
                              struct kvm_memory_slot *slot, gfn_t gfn,
                              int level, pte_t unused)
{
        u64 *sptep;
        struct rmap_iterator iter;

        for_each_rmap_spte(rmap_head, &iter, sptep)
                if (is_accessed_spte(*sptep))
                        return true;
        return false;
}

#define RMAP_RECYCLE_THRESHOLD 1000

static void __rmap_add(struct kvm *kvm,
                       struct kvm_mmu_memory_cache *cache,
                       const struct kvm_memory_slot *slot,
                       u64 *spte, gfn_t gfn, unsigned int access)
{
        struct kvm_mmu_page *sp;
        struct kvm_rmap_head *rmap_head;
        int rmap_count;

        sp = sptep_to_sp(spte);
        kvm_mmu_page_set_translation(sp, spte_index(spte), gfn, access);
        kvm_update_page_stats(kvm, sp->role.level, 1);

        rmap_head = gfn_to_rmap(gfn, sp->role.level, slot);
        rmap_count = pte_list_add(cache, spte, rmap_head);

        if (rmap_count > kvm->stat.max_mmu_rmap_size)
                kvm->stat.max_mmu_rmap_size = rmap_count;
        if (rmap_count > RMAP_RECYCLE_THRESHOLD) {
                kvm_zap_all_rmap_sptes(kvm, rmap_head);
                kvm_flush_remote_tlbs_with_address(
                                kvm, sp->gfn, KVM_PAGES_PER_HPAGE(sp->role.level));
        }
}

static void rmap_add(struct kvm_vcpu *vcpu, const struct kvm_memory_slot *slot,
                     u64 *spte, gfn_t gfn, unsigned int access)
{
        struct kvm_mmu_memory_cache *cache = &vcpu->arch.mmu_pte_list_desc_cache;

        __rmap_add(vcpu->kvm, cache, slot, spte, gfn, access);
}

bool kvm_age_gfn(struct kvm *kvm, struct kvm_gfn_range *range)
{
        bool young = false;

        if (kvm_memslots_have_rmaps(kvm))
                young = kvm_handle_gfn_range(kvm, range, kvm_age_rmap);

        if (tdp_mmu_enabled)
                young |= kvm_tdp_mmu_age_gfn_range(kvm, range);

        return young;
}

bool kvm_test_age_gfn(struct kvm *kvm, struct kvm_gfn_range *range)
{
        bool young = false;

        if (kvm_memslots_have_rmaps(kvm))
                young = kvm_handle_gfn_range(kvm, range, kvm_test_age_rmap);

        if (tdp_mmu_enabled)
                young |= kvm_tdp_mmu_test_age_gfn(kvm, range);

        return young;
}

#ifdef MMU_DEBUG
static int is_empty_shadow_page(u64 *spt)
{
        u64 *pos;
        u64 *end;

        for (pos = spt, end = pos + SPTE_ENT_PER_PAGE; pos != end; pos++)
                if (is_shadow_present_pte(*pos)) {
                        printk(KERN_ERR "%s: %p %llx\n", __func__,
                               pos, *pos);
                        return 0;
                }
        return 1;
}
#endif

/*
 * This value is the sum of all of the kvm instances's
 * kvm->arch.n_used_mmu_pages values.  We need a global,
 * aggregate version in order to make the slab shrinker
 * faster
 */
static inline void kvm_mod_used_mmu_pages(struct kvm *kvm, long nr)
{
        kvm->arch.n_used_mmu_pages += nr;
        percpu_counter_add(&kvm_total_used_mmu_pages, nr);
}

static void kvm_account_mmu_page(struct kvm *kvm, struct kvm_mmu_page *sp)
{
        kvm_mod_used_mmu_pages(kvm, +1);
        kvm_account_pgtable_pages((void *)sp->spt, +1);
}

static void kvm_unaccount_mmu_page(struct kvm *kvm, struct kvm_mmu_page *sp)
{
        kvm_mod_used_mmu_pages(kvm, -1);
        kvm_account_pgtable_pages((void *)sp->spt, -1);
}

static void kvm_mmu_free_shadow_page(struct kvm_mmu_page *sp)
{
        MMU_WARN_ON(!is_empty_shadow_page(sp->spt));
        hlist_del(&sp->hash_link);
        list_del(&sp->link);
        free_page((unsigned long)sp->spt);
        if (!sp->role.direct)
                free_page((unsigned long)sp->shadowed_translation);
        kmem_cache_free(mmu_page_header_cache, sp);
}

static unsigned kvm_page_table_hashfn(gfn_t gfn)
{
        return hash_64(gfn, KVM_MMU_HASH_SHIFT);
}

static void mmu_page_add_parent_pte(struct kvm_mmu_memory_cache *cache,
                                    struct kvm_mmu_page *sp, u64 *parent_pte)
{
        if (!parent_pte)
                return;

        pte_list_add(cache, parent_pte, &sp->parent_ptes);
}

static void mmu_page_remove_parent_pte(struct kvm_mmu_page *sp,
                                       u64 *parent_pte)
{
        pte_list_remove(parent_pte, &sp->parent_ptes);
}

static void drop_parent_pte(struct kvm_mmu_page *sp,
                            u64 *parent_pte)
{
        mmu_page_remove_parent_pte(sp, parent_pte);
        mmu_spte_clear_no_track(parent_pte);
}

static void mark_unsync(u64 *spte);
static void kvm_mmu_mark_parents_unsync(struct kvm_mmu_page *sp)
{
        u64 *sptep;
        struct rmap_iterator iter;

        for_each_rmap_spte(&sp->parent_ptes, &iter, sptep) {
                mark_unsync(sptep);
        }
}

static void mark_unsync(u64 *spte)
{
        struct kvm_mmu_page *sp;

        sp = sptep_to_sp(spte);
        if (__test_and_set_bit(spte_index(spte), sp->unsync_child_bitmap))
                return;
        if (sp->unsync_children++)
                return;
        kvm_mmu_mark_parents_unsync(sp);
}

static int nonpaging_sync_page(struct kvm_vcpu *vcpu,
                               struct kvm_mmu_page *sp)
{
        return -1;
}

#define KVM_PAGE_ARRAY_NR 16

struct kvm_mmu_pages {
        struct mmu_page_and_offset {
                struct kvm_mmu_page *sp;
                unsigned int idx;
        } page[KVM_PAGE_ARRAY_NR];
        unsigned int nr;
};

static int mmu_pages_add(struct kvm_mmu_pages *pvec, struct kvm_mmu_page *sp,
                         int idx)
{
        int i;

        if (sp->unsync)
                for (i=0; i < pvec->nr; i++)
                        if (pvec->page[i].sp == sp)
                                return 0;

        pvec->page[pvec->nr].sp = sp;
        pvec->page[pvec->nr].idx = idx;
        pvec->nr++;
        return (pvec->nr == KVM_PAGE_ARRAY_NR);
}

static inline void clear_unsync_child_bit(struct kvm_mmu_page *sp, int idx)
{
        --sp->unsync_children;
        WARN_ON((int)sp->unsync_children < 0);
        __clear_bit(idx, sp->unsync_child_bitmap);
}

static int __mmu_unsync_walk(struct kvm_mmu_page *sp,
                           struct kvm_mmu_pages *pvec)
{
        int i, ret, nr_unsync_leaf = 0;

        for_each_set_bit(i, sp->unsync_child_bitmap, 512) {
                struct kvm_mmu_page *child;
                u64 ent = sp->spt[i];

                if (!is_shadow_present_pte(ent) || is_large_pte(ent)) {
                        clear_unsync_child_bit(sp, i);
                        continue;
                }

                child = spte_to_child_sp(ent);

                if (child->unsync_children) {
                        if (mmu_pages_add(pvec, child, i))
                                return -ENOSPC;

                        ret = __mmu_unsync_walk(child, pvec);
                        if (!ret) {
                                clear_unsync_child_bit(sp, i);
                                continue;
                        } else if (ret > 0) {
                                nr_unsync_leaf += ret;
                        } else
                                return ret;
                } else if (child->unsync) {
                        nr_unsync_leaf++;
                        if (mmu_pages_add(pvec, child, i))
                                return -ENOSPC;
                } else
                        clear_unsync_child_bit(sp, i);
        }

        return nr_unsync_leaf;
}

#define INVALID_INDEX (-1)

static int mmu_unsync_walk(struct kvm_mmu_page *sp,
                           struct kvm_mmu_pages *pvec)
{
        pvec->nr = 0;
        if (!sp->unsync_children)
                return 0;

        mmu_pages_add(pvec, sp, INVALID_INDEX);
        return __mmu_unsync_walk(sp, pvec);
}

static void kvm_unlink_unsync_page(struct kvm *kvm, struct kvm_mmu_page *sp)
{
        WARN_ON(!sp->unsync);
        trace_kvm_mmu_sync_page(sp);
        sp->unsync = 0;
        --kvm->stat.mmu_unsync;
}

static bool kvm_mmu_prepare_zap_page(struct kvm *kvm, struct kvm_mmu_page *sp,
                                     struct list_head *invalid_list);
static void kvm_mmu_commit_zap_page(struct kvm *kvm,
                                    struct list_head *invalid_list);

static bool sp_has_gptes(struct kvm_mmu_page *sp)
{
        if (sp->role.direct)
                return false;

        if (sp->role.passthrough)
                return false;

        return true;
}

#define for_each_valid_sp(_kvm, _sp, _list)                             \
        hlist_for_each_entry(_sp, _list, hash_link)                     \
                if (is_obsolete_sp((_kvm), (_sp))) {                    \
                } else

#define for_each_gfn_valid_sp_with_gptes(_kvm, _sp, _gfn)               \
        for_each_valid_sp(_kvm, _sp,                                    \
          &(_kvm)->arch.mmu_page_hash[kvm_page_table_hashfn(_gfn)])     \
                if ((_sp)->gfn != (_gfn) || !sp_has_gptes(_sp)) {} else

static int kvm_sync_page(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp,
                         struct list_head *invalid_list)
{
        int ret = vcpu->arch.mmu->sync_page(vcpu, sp);

        if (ret < 0)
                kvm_mmu_prepare_zap_page(vcpu->kvm, sp, invalid_list);
        return ret;
}

static bool kvm_mmu_remote_flush_or_zap(struct kvm *kvm,
                                        struct list_head *invalid_list,
                                        bool remote_flush)
{
        if (!remote_flush && list_empty(invalid_list))
                return false;

        if (!list_empty(invalid_list))
                kvm_mmu_commit_zap_page(kvm, invalid_list);
        else
                kvm_flush_remote_tlbs(kvm);
        return true;
}

static bool is_obsolete_sp(struct kvm *kvm, struct kvm_mmu_page *sp)
{
        if (sp->role.invalid)
                return true;

        /* TDP MMU pages do not use the MMU generation. */
        return !is_tdp_mmu_page(sp) &&
               unlikely(sp->mmu_valid_gen != kvm->arch.mmu_valid_gen);
}

struct mmu_page_path {
        struct kvm_mmu_page *parent[PT64_ROOT_MAX_LEVEL];
        unsigned int idx[PT64_ROOT_MAX_LEVEL];
};

#define for_each_sp(pvec, sp, parents, i)                       \
                for (i = mmu_pages_first(&pvec, &parents);      \
                        i < pvec.nr && ({ sp = pvec.page[i].sp; 1;});   \
                        i = mmu_pages_next(&pvec, &parents, i))

static int mmu_pages_next(struct kvm_mmu_pages *pvec,
                          struct mmu_page_path *parents,
                          int i)
{
        int n;

        for (n = i+1; n < pvec->nr; n++) {
                struct kvm_mmu_page *sp = pvec->page[n].sp;
                unsigned idx = pvec->page[n].idx;
                int level = sp->role.level;

                parents->idx[level-1] = idx;
                if (level == PG_LEVEL_4K)
                        break;

                parents->parent[level-2] = sp;
        }

        return n;
}

static int mmu_pages_first(struct kvm_mmu_pages *pvec,
                           struct mmu_page_path *parents)
{
        struct kvm_mmu_page *sp;
        int level;

        if (pvec->nr == 0)
                return 0;

        WARN_ON(pvec->page[0].idx != INVALID_INDEX);

        sp = pvec->page[0].sp;
        level = sp->role.level;
        WARN_ON(level == PG_LEVEL_4K);

        parents->parent[level-2] = sp;

        /* Also set up a sentinel.  Further entries in pvec are all
         * children of sp, so this element is never overwritten.
         */
        parents->parent[level-1] = NULL;
        return mmu_pages_next(pvec, parents, 0);
}

static void mmu_pages_clear_parents(struct mmu_page_path *parents)
{
        struct kvm_mmu_page *sp;
        unsigned int level = 0;

        do {
                unsigned int idx = parents->idx[level];
                sp = parents->parent[level];
                if (!sp)
                        return;

                WARN_ON(idx == INVALID_INDEX);
                clear_unsync_child_bit(sp, idx);
                level++;
        } while (!sp->unsync_children);
}

static int mmu_sync_children(struct kvm_vcpu *vcpu,
                             struct kvm_mmu_page *parent, bool can_yield)
{
        int i;
        struct kvm_mmu_page *sp;
        struct mmu_page_path parents;
        struct kvm_mmu_pages pages;
        LIST_HEAD(invalid_list);
        bool flush = false;

        while (mmu_unsync_walk(parent, &pages)) {
                bool protected = false;

                for_each_sp(pages, sp, parents, i)
                        protected |= kvm_vcpu_write_protect_gfn(vcpu, sp->gfn);

                if (protected) {
                        kvm_mmu_remote_flush_or_zap(vcpu->kvm, &invalid_list, true);
                        flush = false;
                }

                for_each_sp(pages, sp, parents, i) {
                        kvm_unlink_unsync_page(vcpu->kvm, sp);
                        flush |= kvm_sync_page(vcpu, sp, &invalid_list) > 0;
                        mmu_pages_clear_parents(&parents);
                }
                if (need_resched() || rwlock_needbreak(&vcpu->kvm->mmu_lock)) {
                        kvm_mmu_remote_flush_or_zap(vcpu->kvm, &invalid_list, flush);
                        if (!can_yield) {
                                kvm_make_request(KVM_REQ_MMU_SYNC, vcpu);
                                return -EINTR;
                        }

                        cond_resched_rwlock_write(&vcpu->kvm->mmu_lock);
                        flush = false;
                }
        }

        kvm_mmu_remote_flush_or_zap(vcpu->kvm, &invalid_list, flush);
        return 0;
}

static void __clear_sp_write_flooding_count(struct kvm_mmu_page *sp)
{
        atomic_set(&sp->write_flooding_count,  0);
}

static void clear_sp_write_flooding_count(u64 *spte)
{
        __clear_sp_write_flooding_count(sptep_to_sp(spte));
}

/*
 * The vCPU is required when finding indirect shadow pages; the shadow
 * page may already exist and syncing it needs the vCPU pointer in
 * order to read guest page tables.  Direct shadow pages are never
 * unsync, thus @vcpu can be NULL if @role.direct is true.
 */
static struct kvm_mmu_page *kvm_mmu_find_shadow_page(struct kvm *kvm,
                                                     struct kvm_vcpu *vcpu,
                                                     gfn_t gfn,
                                                     struct hlist_head *sp_list,
                                                     union kvm_mmu_page_role role)
{
        struct kvm_mmu_page *sp;
        int ret;
        int collisions = 0;
        LIST_HEAD(invalid_list);

        for_each_valid_sp(kvm, sp, sp_list) {
                if (sp->gfn != gfn) {
                        collisions++;
                        continue;
                }

                if (sp->role.word != role.word) {
                        /*
                         * If the guest is creating an upper-level page, zap
                         * unsync pages for the same gfn.  While it's possible
                         * the guest is using recursive page tables, in all
                         * likelihood the guest has stopped using the unsync
                         * page and is installing a completely unrelated page.
                         * Unsync pages must not be left as is, because the new
                         * upper-level page will be write-protected.
                         */
                        if (role.level > PG_LEVEL_4K && sp->unsync)
                                kvm_mmu_prepare_zap_page(kvm, sp,
                                                         &invalid_list);
                        continue;
                }

                /* unsync and write-flooding only apply to indirect SPs. */
                if (sp->role.direct)
                        goto out;

                if (sp->unsync) {
                        if (KVM_BUG_ON(!vcpu, kvm))
                                break;

                        /*
                         * The page is good, but is stale.  kvm_sync_page does
                         * get the latest guest state, but (unlike mmu_unsync_children)
                         * it doesn't write-protect the page or mark it synchronized!
                         * This way the validity of the mapping is ensured, but the
                         * overhead of write protection is not incurred until the
                         * guest invalidates the TLB mapping.  This allows multiple
                         * SPs for a single gfn to be unsync.
                         *
                         * If the sync fails, the page is zapped.  If so, break
                         * in order to rebuild it.
                         */
                        ret = kvm_sync_page(vcpu, sp, &invalid_list);
                        if (ret < 0)
                                break;

                        WARN_ON(!list_empty(&invalid_list));
                        if (ret > 0)
                                kvm_flush_remote_tlbs(kvm);
                }

                __clear_sp_write_flooding_count(sp);

                goto out;
        }

        sp = NULL;
        ++kvm->stat.mmu_cache_miss;

out:
        kvm_mmu_commit_zap_page(kvm, &invalid_list);

        if (collisions > kvm->stat.max_mmu_page_hash_collisions)
                kvm->stat.max_mmu_page_hash_collisions = collisions;
        return sp;
}

/* Caches used when allocating a new shadow page. */
struct shadow_page_caches {
        struct kvm_mmu_memory_cache *page_header_cache;
        struct kvm_mmu_memory_cache *shadow_page_cache;
        struct kvm_mmu_memory_cache *shadowed_info_cache;
};

static struct kvm_mmu_page *kvm_mmu_alloc_shadow_page(struct kvm *kvm,
                                                      struct shadow_page_caches *caches,
                                                      gfn_t gfn,
                                                      struct hlist_head *sp_list,
                                                      union kvm_mmu_page_role role)
{
        struct kvm_mmu_page *sp;

        sp = kvm_mmu_memory_cache_alloc(caches->page_header_cache);
        sp->spt = kvm_mmu_memory_cache_alloc(caches->shadow_page_cache);
        if (!role.direct)
                sp->shadowed_translation = kvm_mmu_memory_cache_alloc(caches->shadowed_info_cache);

        set_page_private(virt_to_page(sp->spt), (unsigned long)sp);

        INIT_LIST_HEAD(&sp->possible_nx_huge_page_link);

        /*
         * active_mmu_pages must be a FIFO list, as kvm_zap_obsolete_pages()
         * depends on valid pages being added to the head of the list.  See
         * comments in kvm_zap_obsolete_pages().
         */
        sp->mmu_valid_gen = kvm->arch.mmu_valid_gen;
        list_add(&sp->link, &kvm->arch.active_mmu_pages);
        kvm_account_mmu_page(kvm, sp);

        sp->gfn = gfn;
        sp->role = role;
        hlist_add_head(&sp->hash_link, sp_list);
        if (sp_has_gptes(sp))
                account_shadowed(kvm, sp);

        return sp;
}

/* Note, @vcpu may be NULL if @role.direct is true; see kvm_mmu_find_shadow_page. */
static struct kvm_mmu_page *__kvm_mmu_get_shadow_page(struct kvm *kvm,
                                                      struct kvm_vcpu *vcpu,
                                                      struct shadow_page_caches *caches,
                                                      gfn_t gfn,
                                                      union kvm_mmu_page_role role)
{
        struct hlist_head *sp_list;
        struct kvm_mmu_page *sp;
        bool created = false;

        sp_list = &kvm->arch.mmu_page_hash[kvm_page_table_hashfn(gfn)];

        sp = kvm_mmu_find_shadow_page(kvm, vcpu, gfn, sp_list, role);
        if (!sp) {
                created = true;
                sp = kvm_mmu_alloc_shadow_page(kvm, caches, gfn, sp_list, role);
        }

        trace_kvm_mmu_get_page(sp, created);
        return sp;
}

static struct kvm_mmu_page *kvm_mmu_get_shadow_page(struct kvm_vcpu *vcpu,
                                                    gfn_t gfn,
                                                    union kvm_mmu_page_role role)
{
        struct shadow_page_caches caches = {
                .page_header_cache = &vcpu->arch.mmu_page_header_cache,
                .shadow_page_cache = &vcpu->arch.mmu_shadow_page_cache,
                .shadowed_info_cache = &vcpu->arch.mmu_shadowed_info_cache,
        };

        return __kvm_mmu_get_shadow_page(vcpu->kvm, vcpu, &caches, gfn, role);
}

static union kvm_mmu_page_role kvm_mmu_child_role(u64 *sptep, bool direct,
                                                  unsigned int access)
{
        struct kvm_mmu_page *parent_sp = sptep_to_sp(sptep);
        union kvm_mmu_page_role role;

        role = parent_sp->role;
        role.level--;
        role.access = access;
        role.direct = direct;
        role.passthrough = 0;

        /*
         * If the guest has 4-byte PTEs then that means it's using 32-bit,
         * 2-level, non-PAE paging. KVM shadows such guests with PAE paging
         * (i.e. 8-byte PTEs). The difference in PTE size means that KVM must
         * shadow each guest page table with multiple shadow page tables, which
         * requires extra bookkeeping in the role.
         *
         * Specifically, to shadow the guest's page directory (which covers a
         * 4GiB address space), KVM uses 4 PAE page directories, each mapping
         * 1GiB of the address space. @role.quadrant encodes which quarter of
         * the address space each maps.
         *
         * To shadow the guest's page tables (which each map a 4MiB region), KVM
         * uses 2 PAE page tables, each mapping a 2MiB region. For these,
         * @role.quadrant encodes which half of the region they map.
         *
         * Concretely, a 4-byte PDE consumes bits 31:22, while an 8-byte PDE
         * consumes bits 29:21.  To consume bits 31:30, KVM's uses 4 shadow
         * PDPTEs; those 4 PAE page directories are pre-allocated and their
         * quadrant is assigned in mmu_alloc_root().   A 4-byte PTE consumes
         * bits 21:12, while an 8-byte PTE consumes bits 20:12.  To consume
         * bit 21 in the PTE (the child here), KVM propagates that bit to the
         * quadrant, i.e. sets quadrant to '0' or '1'.  The parent 8-byte PDE
         * covers bit 21 (see above), thus the quadrant is calculated from the
         * _least_ significant bit of the PDE index.
         */
        if (role.has_4_byte_gpte) {
                WARN_ON_ONCE(role.level != PG_LEVEL_4K);
                role.quadrant = spte_index(sptep) & 1;
        }

        return role;
}

static struct kvm_mmu_page *kvm_mmu_get_child_sp(struct kvm_vcpu *vcpu,
                                                 u64 *sptep, gfn_t gfn,
                                                 bool direct, unsigned int access)
{
        union kvm_mmu_page_role role;

        if (is_shadow_present_pte(*sptep) && !is_large_pte(*sptep))
                return ERR_PTR(-EEXIST);

        role = kvm_mmu_child_role(sptep, direct, access);
        return kvm_mmu_get_shadow_page(vcpu, gfn, role);
}

static void shadow_walk_init_using_root(struct kvm_shadow_walk_iterator *iterator,
                                        struct kvm_vcpu *vcpu, hpa_t root,
                                        u64 addr)
{
        iterator->addr = addr;
        iterator->shadow_addr = root;
        iterator->level = vcpu->arch.mmu->root_role.level;

        if (iterator->level >= PT64_ROOT_4LEVEL &&
            vcpu->arch.mmu->cpu_role.base.level < PT64_ROOT_4LEVEL &&
            !vcpu->arch.mmu->root_role.direct)
                iterator->level = PT32E_ROOT_LEVEL;

        if (iterator->level == PT32E_ROOT_LEVEL) {
                /*
                 * prev_root is currently only used for 64-bit hosts. So only
                 * the active root_hpa is valid here.
                 */
                BUG_ON(root != vcpu->arch.mmu->root.hpa);

                iterator->shadow_addr
                        = vcpu->arch.mmu->pae_root[(addr >> 30) & 3];
                iterator->shadow_addr &= SPTE_BASE_ADDR_MASK;
                --iterator->level;
                if (!iterator->shadow_addr)
                        iterator->level = 0;
        }
}

static void shadow_walk_init(struct kvm_shadow_walk_iterator *iterator,
                             struct kvm_vcpu *vcpu, u64 addr)
{
        shadow_walk_init_using_root(iterator, vcpu, vcpu->arch.mmu->root.hpa,
                                    addr);
}

static bool shadow_walk_okay(struct kvm_shadow_walk_iterator *iterator)
{
        if (iterator->level < PG_LEVEL_4K)
                return false;

        iterator->index = SPTE_INDEX(iterator->addr, iterator->level);
        iterator->sptep = ((u64 *)__va(iterator->shadow_addr)) + iterator->index;
        return true;
}

static void __shadow_walk_next(struct kvm_shadow_walk_iterator *iterator,
                               u64 spte)
{
        if (!is_shadow_present_pte(spte) || is_last_spte(spte, iterator->level)) {
                iterator->level = 0;
                return;
        }

        iterator->shadow_addr = spte & SPTE_BASE_ADDR_MASK;
        --iterator->level;
}

static void shadow_walk_next(struct kvm_shadow_walk_iterator *iterator)
{
        __shadow_walk_next(iterator, *iterator->sptep);
}

static void __link_shadow_page(struct kvm *kvm,
                               struct kvm_mmu_memory_cache *cache, u64 *sptep,
                               struct kvm_mmu_page *sp, bool flush)
{
        u64 spte;

        BUILD_BUG_ON(VMX_EPT_WRITABLE_MASK != PT_WRITABLE_MASK);

        /*
         * If an SPTE is present already, it must be a leaf and therefore
         * a large one.  Drop it, and flush the TLB if needed, before
         * installing sp.
         */
        if (is_shadow_present_pte(*sptep))
                drop_large_spte(kvm, sptep, flush);

        spte = make_nonleaf_spte(sp->spt, sp_ad_disabled(sp));

        mmu_spte_set(sptep, spte);

        mmu_page_add_parent_pte(cache, sp, sptep);

        /*
         * The non-direct sub-pagetable must be updated before linking.  For
         * L1 sp, the pagetable is updated via kvm_sync_page() in
         * kvm_mmu_find_shadow_page() without write-protecting the gfn,
         * so sp->unsync can be true or false.  For higher level non-direct
         * sp, the pagetable is updated/synced via mmu_sync_children() in
         * FNAME(fetch)(), so sp->unsync_children can only be false.
         * WARN_ON_ONCE() if anything happens unexpectedly.
         */
        if (WARN_ON_ONCE(sp->unsync_children) || sp->unsync)
                mark_unsync(sptep);
}

static void link_shadow_page(struct kvm_vcpu *vcpu, u64 *sptep,
                             struct kvm_mmu_page *sp)
{
        __link_shadow_page(vcpu->kvm, &vcpu->arch.mmu_pte_list_desc_cache, sptep, sp, true);
}

static void validate_direct_spte(struct kvm_vcpu *vcpu, u64 *sptep,
                                   unsigned direct_access)
{
        if (is_shadow_present_pte(*sptep) && !is_large_pte(*sptep)) {
                struct kvm_mmu_page *child;

                /*
                 * For the direct sp, if the guest pte's dirty bit
                 * changed form clean to dirty, it will corrupt the
                 * sp's access: allow writable in the read-only sp,
                 * so we should update the spte at this point to get
                 * a new sp with the correct access.
                 */
                child = spte_to_child_sp(*sptep);
                if (child->role.access == direct_access)
                        return;

                drop_parent_pte(child, sptep);
                kvm_flush_remote_tlbs_with_address(vcpu->kvm, child->gfn, 1);
        }
}

/* Returns the number of zapped non-leaf child shadow pages. */
static int mmu_page_zap_pte(struct kvm *kvm, struct kvm_mmu_page *sp,
                            u64 *spte, struct list_head *invalid_list)
{
        u64 pte;
        struct kvm_mmu_page *child;

        pte = *spte;
        if (is_shadow_present_pte(pte)) {
                if (is_last_spte(pte, sp->role.level)) {
                        drop_spte(kvm, spte);
                } else {
                        child = spte_to_child_sp(pte);
                        drop_parent_pte(child, spte);

                        /*
                         * Recursively zap nested TDP SPs, parentless SPs are
                         * unlikely to be used again in the near future.  This
                         * avoids retaining a large number of stale nested SPs.
                         */
                        if (tdp_enabled && invalid_list &&
                            child->role.guest_mode && !child->parent_ptes.val)
                                return kvm_mmu_prepare_zap_page(kvm, child,
                                                                invalid_list);
                }
        } else if (is_mmio_spte(pte)) {
                mmu_spte_clear_no_track(spte);
        }
        return 0;
}

static int kvm_mmu_page_unlink_children(struct kvm *kvm,
                                        struct kvm_mmu_page *sp,
                                        struct list_head *invalid_list)
{
        int zapped = 0;
        unsigned i;

        for (i = 0; i < SPTE_ENT_PER_PAGE; ++i)
                zapped += mmu_page_zap_pte(kvm, sp, sp->spt + i, invalid_list);

        return zapped;
}

static void kvm_mmu_unlink_parents(struct kvm_mmu_page *sp)
{
        u64 *sptep;
        struct rmap_iterator iter;

        while ((sptep = rmap_get_first(&sp->parent_ptes, &iter)))
                drop_parent_pte(sp, sptep);
}

static int mmu_zap_unsync_children(struct kvm *kvm,
                                   struct kvm_mmu_page *parent,
                                   struct list_head *invalid_list)
{
        int i, zapped = 0;
        struct mmu_page_path parents;
        struct kvm_mmu_pages pages;

        if (parent->role.level == PG_LEVEL_4K)
                return 0;

        while (mmu_unsync_walk(parent, &pages)) {
                struct kvm_mmu_page *sp;

                for_each_sp(pages, sp, parents, i) {
                        kvm_mmu_prepare_zap_page(kvm, sp, invalid_list);
                        mmu_pages_clear_parents(&parents);
                        zapped++;
                }
        }

        return zapped;
}

static bool __kvm_mmu_prepare_zap_page(struct kvm *kvm,
                                       struct kvm_mmu_page *sp,
                                       struct list_head *invalid_list,
                                       int *nr_zapped)
{
        bool list_unstable, zapped_root = false;

        lockdep_assert_held_write(&kvm->mmu_lock);
        trace_kvm_mmu_prepare_zap_page(sp);
        ++kvm->stat.mmu_shadow_zapped;
        *nr_zapped = mmu_zap_unsync_children(kvm, sp, invalid_list);
        *nr_zapped += kvm_mmu_page_unlink_children(kvm, sp, invalid_list);
        kvm_mmu_unlink_parents(sp);

        /* Zapping children means active_mmu_pages has become unstable. */
        list_unstable = *nr_zapped;

        if (!sp->role.invalid && sp_has_gptes(sp))
                unaccount_shadowed(kvm, sp);

        if (sp->unsync)
                kvm_unlink_unsync_page(kvm, sp);
        if (!sp->root_count) {
                /* Count self */
                (*nr_zapped)++;

                /*
                 * Already invalid pages (previously active roots) are not on
                 * the active page list.  See list_del() in the "else" case of
                 * !sp->root_count.
                 */
                if (sp->role.invalid)
                        list_add(&sp->link, invalid_list);
                else
                        list_move(&sp->link, invalid_list);
                kvm_unaccount_mmu_page(kvm, sp);
        } else {
                /*
                 * Remove the active root from the active page list, the root
                 * will be explicitly freed when the root_count hits zero.
                 */
                list_del(&sp->link);

                /*
                 * Obsolete pages cannot be used on any vCPUs, see the comment
                 * in kvm_mmu_zap_all_fast().  Note, is_obsolete_sp() also
                 * treats invalid shadow pages as being obsolete.
                 */
                zapped_root = !is_obsolete_sp(kvm, sp);
        }

        if (sp->nx_huge_page_disallowed)
                unaccount_nx_huge_page(kvm, sp);

        sp->role.invalid = 1;

        /*
         * Make the request to free obsolete roots after marking the root
         * invalid, otherwise other vCPUs may not see it as invalid.
         */
        if (zapped_root)
                kvm_make_all_cpus_request(kvm, KVM_REQ_MMU_FREE_OBSOLETE_ROOTS);
        return list_unstable;
}

static bool kvm_mmu_prepare_zap_page(struct kvm *kvm, struct kvm_mmu_page *sp,
                                     struct list_head *invalid_list)
{
        int nr_zapped;

        __kvm_mmu_prepare_zap_page(kvm, sp, invalid_list, &nr_zapped);
        return nr_zapped;
}

static void kvm_mmu_commit_zap_page(struct kvm *kvm,
                                    struct list_head *invalid_list)
{
        struct kvm_mmu_page *sp, *nsp;

        if (list_empty(invalid_list))
                return;

        /*
         * We need to make sure everyone sees our modifications to
         * the page tables and see changes to vcpu->mode here. The barrier
         * in the kvm_flush_remote_tlbs() achieves this. This pairs
         * with vcpu_enter_guest and walk_shadow_page_lockless_begin/end.
         *
         * In addition, kvm_flush_remote_tlbs waits for all vcpus to exit
         * guest mode and/or lockless shadow page table walks.
         */
        kvm_flush_remote_tlbs(kvm);

        list_for_each_entry_safe(sp, nsp, invalid_list, link) {
                WARN_ON(!sp->role.invalid || sp->root_count);
                kvm_mmu_free_shadow_page(sp);
        }
}

static unsigned long kvm_mmu_zap_oldest_mmu_pages(struct kvm *kvm,
                                                  unsigned long nr_to_zap)
{
        unsigned long total_zapped = 0;
        struct kvm_mmu_page *sp, *tmp;
        LIST_HEAD(invalid_list);
        bool unstable;
        int nr_zapped;

        if (list_empty(&kvm->arch.active_mmu_pages))
                return 0;

restart:
        list_for_each_entry_safe_reverse(sp, tmp, &kvm->arch.active_mmu_pages, link) {
                /*
                 * Don't zap active root pages, the page itself can't be freed
                 * and zapping it will just force vCPUs to realloc and reload.
                 */
                if (sp->root_count)
                        continue;

                unstable = __kvm_mmu_prepare_zap_page(kvm, sp, &invalid_list,
                                                      &nr_zapped);
                total_zapped += nr_zapped;
                if (total_zapped >= nr_to_zap)
                        break;

                if (unstable)
                        goto restart;
        }

        kvm_mmu_commit_zap_page(kvm, &invalid_list);

        kvm->stat.mmu_recycled += total_zapped;
        return total_zapped;
}

static inline unsigned long kvm_mmu_available_pages(struct kvm *kvm)
{
        if (kvm->arch.n_max_mmu_pages > kvm->arch.n_used_mmu_pages)
                return kvm->arch.n_max_mmu_pages -
                        kvm->arch.n_used_mmu_pages;

        return 0;
}

static int make_mmu_pages_available(struct kvm_vcpu *vcpu)
{
        unsigned long avail = kvm_mmu_available_pages(vcpu->kvm);

        if (likely(avail >= KVM_MIN_FREE_MMU_PAGES))
                return 0;

        kvm_mmu_zap_oldest_mmu_pages(vcpu->kvm, KVM_REFILL_PAGES - avail);

        /*
         * Note, this check is intentionally soft, it only guarantees that one
         * page is available, while the caller may end up allocating as many as
         * four pages, e.g. for PAE roots or for 5-level paging.  Temporarily
         * exceeding the (arbitrary by default) limit will not harm the host,
         * being too aggressive may unnecessarily kill the guest, and getting an
         * exact count is far more trouble than it's worth, especially in the
         * page fault paths.
         */
        if (!kvm_mmu_available_pages(vcpu->kvm))
                return -ENOSPC;
        return 0;
}

/*
 * Changing the number of mmu pages allocated to the vm
 * Note: if goal_nr_mmu_pages is too small, you will get dead lock
 */
void kvm_mmu_change_mmu_pages(struct kvm *kvm, unsigned long goal_nr_mmu_pages)
{
        write_lock(&kvm->mmu_lock);

        if (kvm->arch.n_used_mmu_pages > goal_nr_mmu_pages) {
                kvm_mmu_zap_oldest_mmu_pages(kvm, kvm->arch.n_used_mmu_pages -
                                                  goal_nr_mmu_pages);

                goal_nr_mmu_pages = kvm->arch.n_used_mmu_pages;
        }

        kvm->arch.n_max_mmu_pages = goal_nr_mmu_pages;

        write_unlock(&kvm->mmu_lock);
}

int kvm_mmu_unprotect_page(struct kvm *kvm, gfn_t gfn)
{
        struct kvm_mmu_page *sp;
        LIST_HEAD(invalid_list);
        int r;

        pgprintk("%s: looking for gfn %llx\n", __func__, gfn);
        r = 0;
        write_lock(&kvm->mmu_lock);
        for_each_gfn_valid_sp_with_gptes(kvm, sp, gfn) {
                pgprintk("%s: gfn %llx role %x\n", __func__, gfn,
                         sp->role.word);
                r = 1;
                kvm_mmu_prepare_zap_page(kvm, sp, &invalid_list);
        }
        kvm_mmu_commit_zap_page(kvm, &invalid_list);
        write_unlock(&kvm->mmu_lock);

        return r;
}

static int kvm_mmu_unprotect_page_virt(struct kvm_vcpu *vcpu, gva_t gva)
{
        gpa_t gpa;
        int r;

        if (vcpu->arch.mmu->root_role.direct)
                return 0;

        gpa = kvm_mmu_gva_to_gpa_read(vcpu, gva, NULL);

        r = kvm_mmu_unprotect_page(vcpu->kvm, gpa >> PAGE_SHIFT);

        return r;
}

static void kvm_unsync_page(struct kvm *kvm, struct kvm_mmu_page *sp)
{
        trace_kvm_mmu_unsync_page(sp);
        ++kvm->stat.mmu_unsync;
        sp->unsync = 1;

        kvm_mmu_mark_parents_unsync(sp);
}

/*
 * Attempt to unsync any shadow pages that can be reached by the specified gfn,
 * KVM is creating a writable mapping for said gfn.  Returns 0 if all pages
 * were marked unsync (or if there is no shadow page), -EPERM if the SPTE must
 * be write-protected.
 */
int mmu_try_to_unsync_pages(struct kvm *kvm, const struct kvm_memory_slot *slot,
                            gfn_t gfn, bool can_unsync, bool prefetch)
{
        struct kvm_mmu_page *sp;
        bool locked = false;

        /*
         * Force write-protection if the page is being tracked.  Note, the page
         * track machinery is used to write-protect upper-level shadow pages,
         * i.e. this guards the role.level == 4K assertion below!
         */
        if (kvm_slot_page_track_is_active(kvm, slot, gfn, KVM_PAGE_TRACK_WRITE))
                return -EPERM;

        /*
         * The page is not write-tracked, mark existing shadow pages unsync
         * unless KVM is synchronizing an unsync SP (can_unsync = false).  In
         * that case, KVM must complete emulation of the guest TLB flush before
         * allowing shadow pages to become unsync (writable by the guest).
         */
        for_each_gfn_valid_sp_with_gptes(kvm, sp, gfn) {
                if (!can_unsync)
                        return -EPERM;

                if (sp->unsync)
                        continue;

                if (prefetch)
                        return -EEXIST;

                /*
                 * TDP MMU page faults require an additional spinlock as they
                 * run with mmu_lock held for read, not write, and the unsync
                 * logic is not thread safe.  Take the spinklock regardless of
                 * the MMU type to avoid extra conditionals/parameters, there's
                 * no meaningful penalty if mmu_lock is held for write.
                 */
                if (!locked) {
                        locked = true;
                        spin_lock(&kvm->arch.mmu_unsync_pages_lock);

                        /*
                         * Recheck after taking the spinlock, a different vCPU
                         * may have since marked the page unsync.  A false
                         * positive on the unprotected check above is not
                         * possible as clearing sp->unsync _must_ hold mmu_lock
                         * for write, i.e. unsync cannot transition from 0->1
                         * while this CPU holds mmu_lock for read (or write).
                         */
                        if (READ_ONCE(sp->unsync))
                                continue;
                }

                WARN_ON(sp->role.level != PG_LEVEL_4K);
                kvm_unsync_page(kvm, sp);
        }
        if (locked)
                spin_unlock(&kvm->arch.mmu_unsync_pages_lock);

        /*
         * We need to ensure that the marking of unsync pages is visible
         * before the SPTE is updated to allow writes because
         * kvm_mmu_sync_roots() checks the unsync flags without holding
         * the MMU lock and so can race with this. If the SPTE was updated
         * before the page had been marked as unsync-ed, something like the
         * following could happen:
         *
         * CPU 1                    CPU 2
         * ---------------------------------------------------------------------
         * 1.2 Host updates SPTE
         *     to be writable
         *                      2.1 Guest writes a GPTE for GVA X.
         *                          (GPTE being in the guest page table shadowed
         *                           by the SP from CPU 1.)
         *                          This reads SPTE during the page table walk.
         *                          Since SPTE.W is read as 1, there is no
         *                          fault.
         *
         *                      2.2 Guest issues TLB flush.
         *                          That causes a VM Exit.
         *
         *                      2.3 Walking of unsync pages sees sp->unsync is
         *                          false and skips the page.
         *
         *                      2.4 Guest accesses GVA X.
         *                          Since the mapping in the SP was not updated,
         *                          so the old mapping for GVA X incorrectly
         *                          gets used.
         * 1.1 Host marks SP
         *     as unsync
         *     (sp->unsync = true)
         *
         * The write barrier below ensures that 1.1 happens before 1.2 and thus
         * the situation in 2.4 does not arise.  It pairs with the read barrier
         * in is_unsync_root(), placed between 2.1's load of SPTE.W and 2.3.
         */
        smp_wmb();

        return 0;
}

static int mmu_set_spte(struct kvm_vcpu *vcpu, struct kvm_memory_slot *slot,
                        u64 *sptep, unsigned int pte_access, gfn_t gfn,
                        kvm_pfn_t pfn, struct kvm_page_fault *fault)
{
        struct kvm_mmu_page *sp = sptep_to_sp(sptep);
        int level = sp->role.level;
        int was_rmapped = 0;
        int ret = RET_PF_FIXED;
        bool flush = false;
        bool wrprot;
        u64 spte;

        /* Prefetching always gets a writable pfn.  */
        bool host_writable = !fault || fault->map_writable;
        bool prefetch = !fault || fault->prefetch;
        bool write_fault = fault && fault->write;

        pgprintk("%s: spte %llx write_fault %d gfn %llx\n", __func__,
                 *sptep, write_fault, gfn);

        if (unlikely(is_noslot_pfn(pfn))) {
                vcpu->stat.pf_mmio_spte_created++;
                mark_mmio_spte(vcpu, sptep, gfn, pte_access);
                return RET_PF_EMULATE;
        }

        if (is_shadow_present_pte(*sptep)) {
                /*
                 * If we overwrite a PTE page pointer with a 2MB PMD, unlink
                 * the parent of the now unreachable PTE.
                 */
                if (level > PG_LEVEL_4K && !is_large_pte(*sptep)) {
                        struct kvm_mmu_page *child;
                        u64 pte = *sptep;

                        child = spte_to_child_sp(pte);
                        drop_parent_pte(child, sptep);
                        flush = true;
                } else if (pfn != spte_to_pfn(*sptep)) {
                        pgprintk("hfn old %llx new %llx\n",
                                 spte_to_pfn(*sptep), pfn);
                        drop_spte(vcpu->kvm, sptep);
                        flush = true;
                } else
                        was_rmapped = 1;
        }

        wrprot = make_spte(vcpu, sp, slot, pte_access, gfn, pfn, *sptep, prefetch,
                           true, host_writable, &spte);

        if (*sptep == spte) {
                ret = RET_PF_SPURIOUS;
        } else {
                flush |= mmu_spte_update(sptep, spte);
                trace_kvm_mmu_set_spte(level, gfn, sptep);
        }

        if (wrprot) {
                if (write_fault)
                        ret = RET_PF_EMULATE;
        }

        if (flush)
                kvm_flush_remote_tlbs_with_address(vcpu->kvm, gfn,
                                KVM_PAGES_PER_HPAGE(level));

        pgprintk("%s: setting spte %llx\n", __func__, *sptep);

        if (!was_rmapped) {
                WARN_ON_ONCE(ret == RET_PF_SPURIOUS);
                rmap_add(vcpu, slot, sptep, gfn, pte_access);
        } else {
                /* Already rmapped but the pte_access bits may have changed. */
                kvm_mmu_page_set_access(sp, spte_index(sptep), pte_access);
        }

        return ret;
}

static int direct_pte_prefetch_many(struct kvm_vcpu *vcpu,
                                    struct kvm_mmu_page *sp,
                                    u64 *start, u64 *end)
{
        struct page *pages[PTE_PREFETCH_NUM];
        struct kvm_memory_slot *slot;
        unsigned int access = sp->role.access;
        int i, ret;
        gfn_t gfn;

        gfn = kvm_mmu_page_get_gfn(sp, spte_index(start));
        slot = gfn_to_memslot_dirty_bitmap(vcpu, gfn, access & ACC_WRITE_MASK);
        if (!slot)
                return -1;

        ret = gfn_to_page_many_atomic(slot, gfn, pages, end - start);
        if (ret <= 0)
                return -1;

        for (i = 0; i < ret; i++, gfn++, start++) {
                mmu_set_spte(vcpu, slot, start, access, gfn,
                             page_to_pfn(pages[i]), NULL);
                put_page(pages[i]);
        }

        return 0;
}

static void __direct_pte_prefetch(struct kvm_vcpu *vcpu,
                                  struct kvm_mmu_page *sp, u64 *sptep)
{
        u64 *spte, *start = NULL;
        int i;

        WARN_ON(!sp->role.direct);

        i = spte_index(sptep) & ~(PTE_PREFETCH_NUM - 1);
        spte = sp->spt + i;

        for (i = 0; i < PTE_PREFETCH_NUM; i++, spte++) {
                if (is_shadow_present_pte(*spte) || spte == sptep) {
                        if (!start)
                                continue;
                        if (direct_pte_prefetch_many(vcpu, sp, start, spte) < 0)
                                return;
                        start = NULL;
                } else if (!start)
                        start = spte;
        }
        if (start)
                direct_pte_prefetch_many(vcpu, sp, start, spte);
}

static void direct_pte_prefetch(struct kvm_vcpu *vcpu, u64 *sptep)
{
        struct kvm_mmu_page *sp;

        sp = sptep_to_sp(sptep);

        /*
         * Without accessed bits, there's no way to distinguish between
         * actually accessed translations and prefetched, so disable pte
         * prefetch if accessed bits aren't available.
         */
        if (sp_ad_disabled(sp))
                return;

        if (sp->role.level > PG_LEVEL_4K)
                return;

        /*
         * If addresses are being invalidated, skip prefetching to avoid
         * accidentally prefetching those addresses.
         */
        if (unlikely(vcpu->kvm->mmu_invalidate_in_progress))
                return;

        __direct_pte_prefetch(vcpu, sp, sptep);
}

/*
 * Lookup the mapping level for @gfn in the current mm.
 *
 * WARNING!  Use of host_pfn_mapping_level() requires the caller and the end
 * consumer to be tied into KVM's handlers for MMU notifier events!
 *
 * There are several ways to safely use this helper:
 *
 * - Check mmu_invalidate_retry_hva() after grabbing the mapping level, before
 *   consuming it.  In this case, mmu_lock doesn't need to be held during the
 *   lookup, but it does need to be held while checking the MMU notifier.
 *
 * - Hold mmu_lock AND ensure there is no in-progress MMU notifier invalidation
 *   event for the hva.  This can be done by explicit checking the MMU notifier
 *   or by ensuring that KVM already has a valid mapping that covers the hva.
 *
 * - Do not use the result to install new mappings, e.g. use the host mapping
 *   level only to decide whether or not to zap an entry.  In this case, it's
 *   not required to hold mmu_lock (though it's highly likely the caller will
 *   want to hold mmu_lock anyways, e.g. to modify SPTEs).
 *
 * Note!  The lookup can still race with modifications to host page tables, but
 * the above "rules" ensure KVM will not _consume_ the result of the walk if a
 * race with the primary MMU occurs.
 */
static int host_pfn_mapping_level(struct kvm *kvm, gfn_t gfn,
                                  const struct kvm_memory_slot *slot)
{
        int level = PG_LEVEL_4K;
        unsigned long hva;
        unsigned long flags;
        pgd_t pgd;
        p4d_t p4d;
        pud_t pud;
        pmd_t pmd;

        /*
         * Note, using the already-retrieved memslot and __gfn_to_hva_memslot()
         * is not solely for performance, it's also necessary to avoid the
         * "writable" check in __gfn_to_hva_many(), which will always fail on
         * read-only memslots due to gfn_to_hva() assuming writes.  Earlier
         * page fault steps have already verified the guest isn't writing a
         * read-only memslot.
         */
        hva = __gfn_to_hva_memslot(slot, gfn);

        /*
         * Disable IRQs to prevent concurrent tear down of host page tables,
         * e.g. if the primary MMU promotes a P*D to a huge page and then frees
         * the original page table.
         */
        local_irq_save(flags);

        /*
         * Read each entry once.  As above, a non-leaf entry can be promoted to
         * a huge page _during_ this walk.  Re-reading the entry could send the
         * walk into the weeks, e.g. p*d_large() returns false (sees the old
         * value) and then p*d_offset() walks into the target huge page instead
         * of the old page table (sees the new value).
         */
        pgd = READ_ONCE(*pgd_offset(kvm->mm, hva));
        if (pgd_none(pgd))
                goto out;

        p4d = READ_ONCE(*p4d_offset(&pgd, hva));
        if (p4d_none(p4d) || !p4d_present(p4d))
                goto out;

        pud = READ_ONCE(*pud_offset(&p4d, hva));
        if (pud_none(pud) || !pud_present(pud))
                goto out;

        if (pud_large(pud)) {
                level = PG_LEVEL_1G;
                goto out;
        }

        pmd = READ_ONCE(*pmd_offset(&pud, hva));
        if (pmd_none(pmd) || !pmd_present(pmd))
                goto out;

        if (pmd_large(pmd))
                level = PG_LEVEL_2M;

out:
        local_irq_restore(flags);
        return level;
}

int kvm_mmu_max_mapping_level(struct kvm *kvm,
                              const struct kvm_memory_slot *slot, gfn_t gfn,
                              int max_level)
{
        struct kvm_lpage_info *linfo;
        int host_level;

        max_level = min(max_level, max_huge_page_level);
        for ( ; max_level > PG_LEVEL_4K; max_level--) {
                linfo = lpage_info_slot(gfn, slot, max_level);
                if (!linfo->disallow_lpage)
                        break;
        }

        if (max_level == PG_LEVEL_4K)
                return PG_LEVEL_4K;

        host_level = host_pfn_mapping_level(kvm, gfn, slot);
        return min(host_level, max_level);
}

void kvm_mmu_hugepage_adjust(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault)
{
        struct kvm_memory_slot *slot = fault->slot;
        kvm_pfn_t mask;

        fault->huge_page_disallowed = fault->exec && fault->nx_huge_page_workaround_enabled;

        if (unlikely(fault->max_level == PG_LEVEL_4K))
                return;

        if (is_error_noslot_pfn(fault->pfn))
                return;

        if (kvm_slot_dirty_track_enabled(slot))
                return;

        /*
         * Enforce the iTLB multihit workaround after capturing the requested
         * level, which will be used to do precise, accurate accounting.
         */
        fault->req_level = kvm_mmu_max_mapping_level(vcpu->kvm, slot,
                                                     fault->gfn, fault->max_level);
        if (fault->req_level == PG_LEVEL_4K || fault->huge_page_disallowed)
                return;

        /*
         * mmu_invalidate_retry() was successful and mmu_lock is held, so
         * the pmd can't be split from under us.
         */
        fault->goal_level = fault->req_level;
        mask = KVM_PAGES_PER_HPAGE(fault->goal_level) - 1;
        VM_BUG_ON((fault->gfn & mask) != (fault->pfn & mask));
        fault->pfn &= ~mask;
}

void disallowed_hugepage_adjust(struct kvm_page_fault *fault, u64 spte, int cur_level)
{
        if (cur_level > PG_LEVEL_4K &&
            cur_level == fault->goal_level &&
            is_shadow_present_pte(spte) &&
            !is_large_pte(spte) &&
            spte_to_child_sp(spte)->nx_huge_page_disallowed) {
                /*
                 * A small SPTE exists for this pfn, but FNAME(fetch),
                 * direct_map(), or kvm_tdp_mmu_map() would like to create a
                 * large PTE instead: just force them to go down another level,
                 * patching back for them into pfn the next 9 bits of the
                 * address.
                 */
                u64 page_mask = KVM_PAGES_PER_HPAGE(cur_level) -
                                KVM_PAGES_PER_HPAGE(cur_level - 1);
                fault->pfn |= fault->gfn & page_mask;
                fault->goal_level--;
        }
}

static int direct_map(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault)
{
        struct kvm_shadow_walk_iterator it;
        struct kvm_mmu_page *sp;
        int ret;
        gfn_t base_gfn = fault->gfn;

        kvm_mmu_hugepage_adjust(vcpu, fault);

        trace_kvm_mmu_spte_requested(fault);
        for_each_shadow_entry(vcpu, fault->addr, it) {
                /*
                 * We cannot overwrite existing page tables with an NX
                 * large page, as the leaf could be executable.
                 */
                if (fault->nx_huge_page_workaround_enabled)
                        disallowed_hugepage_adjust(fault, *it.sptep, it.level);

                base_gfn = fault->gfn & ~(KVM_PAGES_PER_HPAGE(it.level) - 1);
                if (it.level == fault->goal_level)
                        break;

                sp = kvm_mmu_get_child_sp(vcpu, it.sptep, base_gfn, true, ACC_ALL);
                if (sp == ERR_PTR(-EEXIST))
                        continue;

                link_shadow_page(vcpu, it.sptep, sp);
                if (fault->huge_page_disallowed)
                        account_nx_huge_page(vcpu->kvm, sp,
                                             fault->req_level >= it.level);
        }

        if (WARN_ON_ONCE(it.level != fault->goal_level))
                return -EFAULT;

        ret = mmu_set_spte(vcpu, fault->slot, it.sptep, ACC_ALL,
                           base_gfn, fault->pfn, fault);
        if (ret == RET_PF_SPURIOUS)
                return ret;

        direct_pte_prefetch(vcpu, it.sptep);
        return ret;
}

static void kvm_send_hwpoison_signal(struct kvm_memory_slot *slot, gfn_t gfn)
{
        unsigned long hva = gfn_to_hva_memslot(slot, gfn);

        send_sig_mceerr(BUS_MCEERR_AR, (void __user *)hva, PAGE_SHIFT, current);
}

static int kvm_handle_error_pfn(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault)
{
        if (is_sigpending_pfn(fault->pfn)) {
                kvm_handle_signal_exit(vcpu);
                return -EINTR;
        }

        /*
         * Do not cache the mmio info caused by writing the readonly gfn
         * into the spte otherwise read access on readonly gfn also can
         * caused mmio page fault and treat it as mmio access.
         */
        if (fault->pfn == KVM_PFN_ERR_RO_FAULT)
                return RET_PF_EMULATE;

        if (fault->pfn == KVM_PFN_ERR_HWPOISON) {
                kvm_send_hwpoison_signal(fault->slot, fault->gfn);
                return RET_PF_RETRY;
        }

        return -EFAULT;
}

static int kvm_handle_noslot_fault(struct kvm_vcpu *vcpu,
                                   struct kvm_page_fault *fault,
                                   unsigned int access)
{
        gva_t gva = fault->is_tdp ? 0 : fault->addr;

        vcpu_cache_mmio_info(vcpu, gva, fault->gfn,
                             access & shadow_mmio_access_mask);

        /*
         * If MMIO caching is disabled, emulate immediately without
         * touching the shadow page tables as attempting to install an
         * MMIO SPTE will just be an expensive nop.
         */
        if (unlikely(!enable_mmio_caching))
                return RET_PF_EMULATE;

        /*
         * Do not create an MMIO SPTE for a gfn greater than host.MAXPHYADDR,
         * any guest that generates such gfns is running nested and is being
         * tricked by L0 userspace (you can observe gfn > L1.MAXPHYADDR if and
         * only if L1's MAXPHYADDR is inaccurate with respect to the
         * hardware's).
         */
        if (unlikely(fault->gfn > kvm_mmu_max_gfn()))
                return RET_PF_EMULATE;

        return RET_PF_CONTINUE;
}

static bool page_fault_can_be_fast(struct kvm_page_fault *fault)
{
        /*
         * Page faults with reserved bits set, i.e. faults on MMIO SPTEs, only
         * reach the common page fault handler if the SPTE has an invalid MMIO
         * generation number.  Refreshing the MMIO generation needs to go down
         * the slow path.  Note, EPT Misconfigs do NOT set the PRESENT flag!
         */
        if (fault->rsvd)
                return false;

        /*
         * #PF can be fast if:
         *
         * 1. The shadow page table entry is not present and A/D bits are
         *    disabled _by KVM_, which could mean that the fault is potentially
         *    caused by access tracking (if enabled).  If A/D bits are enabled
         *    by KVM, but disabled by L1 for L2, KVM is forced to disable A/D
         *    bits for L2 and employ access tracking, but the fast page fault
         *    mechanism only supports direct MMUs.
         * 2. The shadow page table entry is present, the access is a write,
         *    and no reserved bits are set (MMIO SPTEs cannot be "fixed"), i.e.
         *    the fault was caused by a write-protection violation.  If the
         *    SPTE is MMU-writable (determined later), the fault can be fixed
         *    by setting the Writable bit, which can be done out of mmu_lock.
         */
        if (!fault->present)
                return !kvm_ad_enabled();

        /*
         * Note, instruction fetches and writes are mutually exclusive, ignore
         * the "exec" flag.
         */
        return fault->write;
}

/*
 * Returns true if the SPTE was fixed successfully. Otherwise,
 * someone else modified the SPTE from its original value.
 */
static bool
fast_pf_fix_direct_spte(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault,
                        u64 *sptep, u64 old_spte, u64 new_spte)
{
        /*
         * Theoretically we could also set dirty bit (and flush TLB) here in
         * order to eliminate unnecessary PML logging. See comments in
         * set_spte. But fast_page_fault is very unlikely to happen with PML
         * enabled, so we do not do this. This might result in the same GPA
         * to be logged in PML buffer again when the write really happens, and
         * eventually to be called by mark_page_dirty twice. But it's also no
         * harm. This also avoids the TLB flush needed after setting dirty bit
         * so non-PML cases won't be impacted.
         *
         * Compare with set_spte where instead shadow_dirty_mask is set.
         */
        if (!try_cmpxchg64(sptep, &old_spte, new_spte))
                return false;

        if (is_writable_pte(new_spte) && !is_writable_pte(old_spte))
                mark_page_dirty_in_slot(vcpu->kvm, fault->slot, fault->gfn);

        return true;
}

static bool is_access_allowed(struct kvm_page_fault *fault, u64 spte)
{
        if (fault->exec)
                return is_executable_pte(spte);

        if (fault->write)
                return is_writable_pte(spte);

        /* Fault was on Read access */
        return spte & PT_PRESENT_MASK;
}

/*
 * Returns the last level spte pointer of the shadow page walk for the given
 * gpa, and sets *spte to the spte value. This spte may be non-preset. If no
 * walk could be performed, returns NULL and *spte does not contain valid data.
 *
 * Contract:
 *  - Must be called between walk_shadow_page_lockless_{begin,end}.
 *  - The returned sptep must not be used after walk_shadow_page_lockless_end.
 */
static u64 *fast_pf_get_last_sptep(struct kvm_vcpu *vcpu, gpa_t gpa, u64 *spte)
{
        struct kvm_shadow_walk_iterator iterator;
        u64 old_spte;
        u64 *sptep = NULL;

        for_each_shadow_entry_lockless(vcpu, gpa, iterator, old_spte) {
                sptep = iterator.sptep;
                *spte = old_spte;
        }

        return sptep;
}

/*
 * Returns one of RET_PF_INVALID, RET_PF_FIXED or RET_PF_SPURIOUS.
 */
static int fast_page_fault(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault)
{
        struct kvm_mmu_page *sp;
        int ret = RET_PF_INVALID;
        u64 spte = 0ull;
        u64 *sptep = NULL;
        uint retry_count = 0;

        if (!page_fault_can_be_fast(fault))
                return ret;

        walk_shadow_page_lockless_begin(vcpu);

        do {
                u64 new_spte;

                if (tdp_mmu_enabled)
                        sptep = kvm_tdp_mmu_fast_pf_get_last_sptep(vcpu, fault->addr, &spte);
                else
                        sptep = fast_pf_get_last_sptep(vcpu, fault->addr, &spte);

                if (!is_shadow_present_pte(spte))
                        break;

                sp = sptep_to_sp(sptep);
                if (!is_last_spte(spte, sp->role.level))
                        break;

                /*
                 * Check whether the memory access that caused the fault would
                 * still cause it if it were to be performed right now. If not,
                 * then this is a spurious fault caused by TLB lazily flushed,
                 * or some other CPU has already fixed the PTE after the
                 * current CPU took the fault.
                 *
                 * Need not check the access of upper level table entries since
                 * they are always ACC_ALL.
                 */
                if (is_access_allowed(fault, spte)) {
                        ret = RET_PF_SPURIOUS;
                        break;
                }

                new_spte = spte;

                /*
                 * KVM only supports fixing page faults outside of MMU lock for
                 * direct MMUs, nested MMUs are always indirect, and KVM always
                 * uses A/D bits for non-nested MMUs.  Thus, if A/D bits are
                 * enabled, the SPTE can't be an access-tracked SPTE.
                 */
                if (unlikely(!kvm_ad_enabled()) && is_access_track_spte(spte))
                        new_spte = restore_acc_track_spte(new_spte);

                /*
                 * To keep things simple, only SPTEs that are MMU-writable can
                 * be made fully writable outside of mmu_lock, e.g. only SPTEs
                 * that were write-protected for dirty-logging or access
                 * tracking are handled here.  Don't bother checking if the
                 * SPTE is writable to prioritize running with A/D bits enabled.
                 * The is_access_allowed() check above handles the common case
                 * of the fault being spurious, and the SPTE is known to be
                 * shadow-present, i.e. except for access tracking restoration
                 * making the new SPTE writable, the check is wasteful.
                 */
                if (fault->write && is_mmu_writable_spte(spte)) {
                        new_spte |= PT_WRITABLE_MASK;

                        /*
                         * Do not fix write-permission on the large spte when
                         * dirty logging is enabled. Since we only dirty the
                         * first page into the dirty-bitmap in
                         * fast_pf_fix_direct_spte(), other pages are missed
                         * if its slot has dirty logging enabled.
                         *
                         * Instead, we let the slow page fault path create a
                         * normal spte to fix the access.
                         */
                        if (sp->role.level > PG_LEVEL_4K &&
                            kvm_slot_dirty_track_enabled(fault->slot))
                                break;
                }

                /* Verify that the fault can be handled in the fast path */
                if (new_spte == spte ||
                    !is_access_allowed(fault, new_spte))
                        break;

                /*
                 * Currently, fast page fault only works for direct mapping
                 * since the gfn is not stable for indirect shadow page. See
                 * Documentation/virt/kvm/locking.rst to get more detail.
                 */
                if (fast_pf_fix_direct_spte(vcpu, fault, sptep, spte, new_spte)) {
                        ret = RET_PF_FIXED;
                        break;
                }

                if (++retry_count > 4) {
                        printk_once(KERN_WARNING
                                "kvm: Fast #PF retrying more than 4 times.\n");
                        break;
                }

        } while (true);

        trace_fast_page_fault(vcpu, fault, sptep, spte, ret);
        walk_shadow_page_lockless_end(vcpu);

        if (ret != RET_PF_INVALID)
                vcpu->stat.pf_fast++;

        return ret;
}

static void mmu_free_root_page(struct kvm *kvm, hpa_t *root_hpa,
                               struct list_head *invalid_list)
{
        struct kvm_mmu_page *sp;

        if (!VALID_PAGE(*root_hpa))
                return;

        /*
         * The "root" may be a special root, e.g. a PAE entry, treat it as a
         * SPTE to ensure any non-PA bits are dropped.
         */
        sp = spte_to_child_sp(*root_hpa);
        if (WARN_ON(!sp))
                return;

        if (is_tdp_mmu_page(sp))
                kvm_tdp_mmu_put_root(kvm, sp, false);
        else if (!--sp->root_count && sp->role.invalid)
                kvm_mmu_prepare_zap_page(kvm, sp, invalid_list);

        *root_hpa = INVALID_PAGE;
}

/* roots_to_free must be some combination of the KVM_MMU_ROOT_* flags */
void kvm_mmu_free_roots(struct kvm *kvm, struct kvm_mmu *mmu,
                        ulong roots_to_free)
{
        int i;
        LIST_HEAD(invalid_list);
        bool free_active_root;

        BUILD_BUG_ON(KVM_MMU_NUM_PREV_ROOTS >= BITS_PER_LONG);

        /* Before acquiring the MMU lock, see if we need to do any real work. */
        free_active_root = (roots_to_free & KVM_MMU_ROOT_CURRENT)
                && VALID_PAGE(mmu->root.hpa);

        if (!free_active_root) {
                for (i = 0; i < KVM_MMU_NUM_PREV_ROOTS; i++)
                        if ((roots_to_free & KVM_MMU_ROOT_PREVIOUS(i)) &&
                            VALID_PAGE(mmu->prev_roots[i].hpa))
                                break;

                if (i == KVM_MMU_NUM_PREV_ROOTS)
                        return;
        }

        write_lock(&kvm->mmu_lock);

        for (i = 0; i < KVM_MMU_NUM_PREV_ROOTS; i++)
                if (roots_to_free & KVM_MMU_ROOT_PREVIOUS(i))
                        mmu_free_root_page(kvm, &mmu->prev_roots[i].hpa,
                                           &invalid_list);

        if (free_active_root) {
                if (to_shadow_page(mmu->root.hpa)) {
                        mmu_free_root_page(kvm, &mmu->root.hpa, &invalid_list);
                } else if (mmu->pae_root) {
                        for (i = 0; i < 4; ++i) {
                                if (!IS_VALID_PAE_ROOT(mmu->pae_root[i]))
                                        continue;

                                mmu_free_root_page(kvm, &mmu->pae_root[i],
                                                   &invalid_list);
                                mmu->pae_root[i] = INVALID_PAE_ROOT;
                        }
                }
                mmu->root.hpa = INVALID_PAGE;
                mmu->root.pgd = 0;
        }

        kvm_mmu_commit_zap_page(kvm, &invalid_list);
        write_unlock(&kvm->mmu_lock);
}
EXPORT_SYMBOL_GPL(kvm_mmu_free_roots);

void kvm_mmu_free_guest_mode_roots(struct kvm *kvm, struct kvm_mmu *mmu)
{
        unsigned long roots_to_free = 0;
        hpa_t root_hpa;
        int i;

        /*
         * This should not be called while L2 is active, L2 can't invalidate
         * _only_ its own roots, e.g. INVVPID unconditionally exits.
         */
        WARN_ON_ONCE(mmu->root_role.guest_mode);

        for (i = 0; i < KVM_MMU_NUM_PREV_ROOTS; i++) {
                root_hpa = mmu->prev_roots[i].hpa;
                if (!VALID_PAGE(root_hpa))
                        continue;

                if (!to_shadow_page(root_hpa) ||
                        to_shadow_page(root_hpa)->role.guest_mode)
                        roots_to_free |= KVM_MMU_ROOT_PREVIOUS(i);
        }

        kvm_mmu_free_roots(kvm, mmu, roots_to_free);
}
EXPORT_SYMBOL_GPL(kvm_mmu_free_guest_mode_roots);


static int mmu_check_root(struct kvm_vcpu *vcpu, gfn_t root_gfn)
{
        int ret = 0;

        if (!kvm_vcpu_is_visible_gfn(vcpu, root_gfn)) {
                kvm_make_request(KVM_REQ_TRIPLE_FAULT, vcpu);
                ret = 1;
        }

        return ret;
}

static hpa_t mmu_alloc_root(struct kvm_vcpu *vcpu, gfn_t gfn, int quadrant,
                            u8 level)
{
        union kvm_mmu_page_role role = vcpu->arch.mmu->root_role;
        struct kvm_mmu_page *sp;

        role.level = level;
        role.quadrant = quadrant;

        WARN_ON_ONCE(quadrant && !role.has_4_byte_gpte);
        WARN_ON_ONCE(role.direct && role.has_4_byte_gpte);

        sp = kvm_mmu_get_shadow_page(vcpu, gfn, role);
        ++sp->root_count;

        return __pa(sp->spt);
}

static int mmu_alloc_direct_roots(struct kvm_vcpu *vcpu)
{
        struct kvm_mmu *mmu = vcpu->arch.mmu;
        u8 shadow_root_level = mmu->root_role.level;
        hpa_t root;
        unsigned i;
        int r;

        write_lock(&vcpu->kvm->mmu_lock);
        r = make_mmu_pages_available(vcpu);
        if (r < 0)
                goto out_unlock;

        if (tdp_mmu_enabled) {
                root = kvm_tdp_mmu_get_vcpu_root_hpa(vcpu);
                mmu->root.hpa = root;
        } else if (shadow_root_level >= PT64_ROOT_4LEVEL) {
                root = mmu_alloc_root(vcpu, 0, 0, shadow_root_level);
                mmu->root.hpa = root;
        } else if (shadow_root_level == PT32E_ROOT_LEVEL) {
                if (WARN_ON_ONCE(!mmu->pae_root)) {
                        r = -EIO;
                        goto out_unlock;
                }

                for (i = 0; i < 4; ++i) {
                        WARN_ON_ONCE(IS_VALID_PAE_ROOT(mmu->pae_root[i]));

                        root = mmu_alloc_root(vcpu, i << (30 - PAGE_SHIFT), 0,
                                              PT32_ROOT_LEVEL);
                        mmu->pae_root[i] = root | PT_PRESENT_MASK |
                                           shadow_me_value;
                }
                mmu->root.hpa = __pa(mmu->pae_root);
        } else {
                WARN_ONCE(1, "Bad TDP root level = %d\n", shadow_root_level);
                r = -EIO;
                goto out_unlock;
        }

        /* root.pgd is ignored for direct MMUs. */
        mmu->root.pgd = 0;
out_unlock:
        write_unlock(&vcpu->kvm->mmu_lock);
        return r;
}

static int mmu_first_shadow_root_alloc(struct kvm *kvm)
{
        struct kvm_memslots *slots;
        struct kvm_memory_slot *slot;
        int r = 0, i, bkt;

        /*
         * Check if this is the first shadow root being allocated before
         * taking the lock.
         */
        if (kvm_shadow_root_allocated(kvm))
                return 0;

        mutex_lock(&kvm->slots_arch_lock);

        /* Recheck, under the lock, whether this is the first shadow root. */
        if (kvm_shadow_root_allocated(kvm))
                goto out_unlock;

        /*
         * Check if anything actually needs to be allocated, e.g. all metadata
         * will be allocated upfront if TDP is disabled.
         */
        if (kvm_memslots_have_rmaps(kvm) &&
            kvm_page_track_write_tracking_enabled(kvm))
                goto out_success;

        for (i = 0; i < KVM_ADDRESS_SPACE_NUM; i++) {
                slots = __kvm_memslots(kvm, i);
                kvm_for_each_memslot(slot, bkt, slots) {
                        /*
                         * Both of these functions are no-ops if the target is
                         * already allocated, so unconditionally calling both
                         * is safe.  Intentionally do NOT free allocations on
                         * failure to avoid having to track which allocations
                         * were made now versus when the memslot was created.
                         * The metadata is guaranteed to be freed when the slot
                         * is freed, and will be kept/used if userspace retries
                         * KVM_RUN instead of killing the VM.
                         */
                        r = memslot_rmap_alloc(slot, slot->npages);
                        if (r)
                                goto out_unlock;
                        r = kvm_page_track_write_tracking_alloc(slot);
                        if (r)
                                goto out_unlock;
                }
        }

        /*
         * Ensure that shadow_root_allocated becomes true strictly after
         * all the related pointers are set.
         */
out_success:
        smp_store_release(&kvm->arch.shadow_root_allocated, true);

out_unlock:
        mutex_unlock(&kvm->slots_arch_lock);
        return r;
}

static int mmu_alloc_shadow_roots(struct kvm_vcpu *vcpu)
{
        struct kvm_mmu *mmu = vcpu->arch.mmu;
        u64 pdptrs[4], pm_mask;
        gfn_t root_gfn, root_pgd;
        int quadrant, i, r;
        hpa_t root;

        root_pgd = mmu->get_guest_pgd(vcpu);
        root_gfn = root_pgd >> PAGE_SHIFT;

        if (mmu_check_root(vcpu, root_gfn))
                return 1;

        /*
         * On SVM, reading PDPTRs might access guest memory, which might fault
         * and thus might sleep.  Grab the PDPTRs before acquiring mmu_lock.
         */
        if (mmu->cpu_role.base.level == PT32E_ROOT_LEVEL) {
                for (i = 0; i < 4; ++i) {
                        pdptrs[i] = mmu->get_pdptr(vcpu, i);
                        if (!(pdptrs[i] & PT_PRESENT_MASK))
                                continue;

                        if (mmu_check_root(vcpu, pdptrs[i] >> PAGE_SHIFT))
                                return 1;
                }
        }

        r = mmu_first_shadow_root_alloc(vcpu->kvm);
        if (r)
                return r;

        write_lock(&vcpu->kvm->mmu_lock);
        r = make_mmu_pages_available(vcpu);
        if (r < 0)
                goto out_unlock;

        /*
         * Do we shadow a long mode page table? If so we need to
         * write-protect the guests page table root.
         */
        if (mmu->cpu_role.base.level >= PT64_ROOT_4LEVEL) {
                root = mmu_alloc_root(vcpu, root_gfn, 0,
                                      mmu->root_role.level);
                mmu->root.hpa = root;
                goto set_root_pgd;
        }

        if (WARN_ON_ONCE(!mmu->pae_root)) {
                r = -EIO;
                goto out_unlock;
        }

        /*
         * We shadow a 32 bit page table. This may be a legacy 2-level
         * or a PAE 3-level page table. In either case we need to be aware that
         * the shadow page table may be a PAE or a long mode page table.
         */
        pm_mask = PT_PRESENT_MASK | shadow_me_value;
        if (mmu->root_role.level >= PT64_ROOT_4LEVEL) {
                pm_mask |= PT_ACCESSED_MASK | PT_WRITABLE_MASK | PT_USER_MASK;

                if (WARN_ON_ONCE(!mmu->pml4_root)) {
                        r = -EIO;
                        goto out_unlock;
                }
                mmu->pml4_root[0] = __pa(mmu->pae_root) | pm_mask;

                if (mmu->root_role.level == PT64_ROOT_5LEVEL) {
                        if (WARN_ON_ONCE(!mmu->pml5_root)) {
                                r = -EIO;
                                goto out_unlock;
                        }
                        mmu->pml5_root[0] = __pa(mmu->pml4_root) | pm_mask;
                }
        }

        for (i = 0; i < 4; ++i) {
                WARN_ON_ONCE(IS_VALID_PAE_ROOT(mmu->pae_root[i]));

                if (mmu->cpu_role.base.level == PT32E_ROOT_LEVEL) {
                        if (!(pdptrs[i] & PT_PRESENT_MASK)) {
                                mmu->pae_root[i] = INVALID_PAE_ROOT;
                                continue;
                        }
                        root_gfn = pdptrs[i] >> PAGE_SHIFT;
                }

                /*
                 * If shadowing 32-bit non-PAE page tables, each PAE page
                 * directory maps one quarter of the guest's non-PAE page
                 * directory. Othwerise each PAE page direct shadows one guest
                 * PAE page directory so that quadrant should be 0.
                 */
                quadrant = (mmu->cpu_role.base.level == PT32_ROOT_LEVEL) ? i : 0;

                root = mmu_alloc_root(vcpu, root_gfn, quadrant, PT32_ROOT_LEVEL);
                mmu->pae_root[i] = root | pm_mask;
        }

        if (mmu->root_role.level == PT64_ROOT_5LEVEL)
                mmu->root.hpa = __pa(mmu->pml5_root);
        else if (mmu->root_role.level == PT64_ROOT_4LEVEL)
                mmu->root.hpa = __pa(mmu->pml4_root);
        else
                mmu->root.hpa = __pa(mmu->pae_root);

set_root_pgd:
        mmu->root.pgd = root_pgd;
out_unlock:
        write_unlock(&vcpu->kvm->mmu_lock);

        return r;
}

static int mmu_alloc_special_roots(struct kvm_vcpu *vcpu)
{
        struct kvm_mmu *mmu = vcpu->arch.mmu;
        bool need_pml5 = mmu->root_role.level > PT64_ROOT_4LEVEL;
        u64 *pml5_root = NULL;
        u64 *pml4_root = NULL;
        u64 *pae_root;

        /*
         * When shadowing 32-bit or PAE NPT with 64-bit NPT, the PML4 and PDP
         * tables are allocated and initialized at root creation as there is no
         * equivalent level in the guest's NPT to shadow.  Allocate the tables
         * on demand, as running a 32-bit L1 VMM on 64-bit KVM is very rare.
         */
        if (mmu->root_role.direct ||
            mmu->cpu_role.base.level >= PT64_ROOT_4LEVEL ||
            mmu->root_role.level < PT64_ROOT_4LEVEL)
                return 0;

        /*
         * NPT, the only paging mode that uses this horror, uses a fixed number
         * of levels for the shadow page tables, e.g. all MMUs are 4-level or
         * all MMus are 5-level.  Thus, this can safely require that pml5_root
         * is allocated if the other roots are valid and pml5 is needed, as any
         * prior MMU would also have required pml5.
         */
        if (mmu->pae_root && mmu->pml4_root && (!need_pml5 || mmu->pml5_root))
                return 0;

        /*
         * The special roots should always be allocated in concert.  Yell and
         * bail if KVM ends up in a state where only one of the roots is valid.
         */
        if (WARN_ON_ONCE(!tdp_enabled || mmu->pae_root || mmu->pml4_root ||
                         (need_pml5 && mmu->pml5_root)))
                return -EIO;

        /*
         * Unlike 32-bit NPT, the PDP table doesn't need to be in low mem, and
         * doesn't need to be decrypted.
         */
        pae_root = (void *)get_zeroed_page(GFP_KERNEL_ACCOUNT);
        if (!pae_root)
                return -ENOMEM;

#ifdef CONFIG_X86_64
        pml4_root = (void *)get_zeroed_page(GFP_KERNEL_ACCOUNT);
        if (!pml4_root)
                goto err_pml4;

        if (need_pml5) {
                pml5_root = (void *)get_zeroed_page(GFP_KERNEL_ACCOUNT);
                if (!pml5_root)
                        goto err_pml5;
        }
#endif

        mmu->pae_root = pae_root;
        mmu->pml4_root = pml4_root;
        mmu->pml5_root = pml5_root;

        return 0;

#ifdef CONFIG_X86_64
err_pml5:
        free_page((unsigned long)pml4_root);
err_pml4:
        free_page((unsigned long)pae_root);
        return -ENOMEM;
#endif
}

static bool is_unsync_root(hpa_t root)
{
        struct kvm_mmu_page *sp;

        if (!VALID_PAGE(root))
                return false;

        /*
         * The read barrier orders the CPU's read of SPTE.W during the page table
         * walk before the reads of sp->unsync/sp->unsync_children here.
         *
         * Even if another CPU was marking the SP as unsync-ed simultaneously,
         * any guest page table changes are not guaranteed to be visible anyway
         * until this VCPU issues a TLB flush strictly after those changes are
         * made.  We only need to ensure that the other CPU sets these flags
         * before any actual changes to the page tables are made.  The comments
         * in mmu_try_to_unsync_pages() describe what could go wrong if this
         * requirement isn't satisfied.
         */
        smp_rmb();
        sp = to_shadow_page(root);

        /*
         * PAE roots (somewhat arbitrarily) aren't backed by shadow pages, the
         * PDPTEs for a given PAE root need to be synchronized individually.
         */
        if (WARN_ON_ONCE(!sp))
                return false;

        if (sp->unsync || sp->unsync_children)
                return true;

        return false;
}

void kvm_mmu_sync_roots(struct kvm_vcpu *vcpu)
{
        int i;
        struct kvm_mmu_page *sp;

        if (vcpu->arch.mmu->root_role.direct)
                return;

        if (!VALID_PAGE(vcpu->arch.mmu->root.hpa))
                return;

        vcpu_clear_mmio_info(vcpu, MMIO_GVA_ANY);

        if (vcpu->arch.mmu->cpu_role.base.level >= PT64_ROOT_4LEVEL) {
                hpa_t root = vcpu->arch.mmu->root.hpa;
                sp = to_shadow_page(root);

                if (!is_unsync_root(root))
                        return;

                write_lock(&vcpu->kvm->mmu_lock);
                mmu_sync_children(vcpu, sp, true);
                write_unlock(&vcpu->kvm->mmu_lock);
                return;
        }

        write_lock(&vcpu->kvm->mmu_lock);

        for (i = 0; i < 4; ++i) {
                hpa_t root = vcpu->arch.mmu->pae_root[i];

                if (IS_VALID_PAE_ROOT(root)) {
                        sp = spte_to_child_sp(root);
                        mmu_sync_children(vcpu, sp, true);
                }
        }

        write_unlock(&vcpu->kvm->mmu_lock);
}

void kvm_mmu_sync_prev_roots(struct kvm_vcpu *vcpu)
{
        unsigned long roots_to_free = 0;
        int i;

        for (i = 0; i < KVM_MMU_NUM_PREV_ROOTS; i++)
                if (is_unsync_root(vcpu->arch.mmu->prev_roots[i].hpa))
                        roots_to_free |= KVM_MMU_ROOT_PREVIOUS(i);

        /* sync prev_roots by simply freeing them */
        kvm_mmu_free_roots(vcpu->kvm, vcpu->arch.mmu, roots_to_free);
}

static gpa_t nonpaging_gva_to_gpa(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu,
                                  gpa_t vaddr, u64 access,
                                  struct x86_exception *exception)
{
        if (exception)
                exception->error_code = 0;
        return kvm_translate_gpa(vcpu, mmu, vaddr, access, exception);
}

static bool mmio_info_in_cache(struct kvm_vcpu *vcpu, u64 addr, bool direct)
{
        /*
         * A nested guest cannot use the MMIO cache if it is using nested
         * page tables, because cr2 is a nGPA while the cache stores GPAs.
         */
        if (mmu_is_nested(vcpu))
                return false;

        if (direct)
                return vcpu_match_mmio_gpa(vcpu, addr);

        return vcpu_match_mmio_gva(vcpu, addr);
}

/*
 * Return the level of the lowest level SPTE added to sptes.
 * That SPTE may be non-present.
 *
 * Must be called between walk_shadow_page_lockless_{begin,end}.
 */
static int get_walk(struct kvm_vcpu *vcpu, u64 addr, u64 *sptes, int *root_level)
{
        struct kvm_shadow_walk_iterator iterator;
        int leaf = -1;
        u64 spte;

        for (shadow_walk_init(&iterator, vcpu, addr),
             *root_level = iterator.level;
             shadow_walk_okay(&iterator);
             __shadow_walk_next(&iterator, spte)) {
                leaf = iterator.level;
                spte = mmu_spte_get_lockless(iterator.sptep);

                sptes[leaf] = spte;
        }

        return leaf;
}

/* return true if reserved bit(s) are detected on a valid, non-MMIO SPTE. */
static bool get_mmio_spte(struct kvm_vcpu *vcpu, u64 addr, u64 *sptep)
{
        u64 sptes[PT64_ROOT_MAX_LEVEL + 1];
        struct rsvd_bits_validate *rsvd_check;
        int root, leaf, level;
        bool reserved = false;

        walk_shadow_page_lockless_begin(vcpu);

        if (is_tdp_mmu_active(vcpu))
                leaf = kvm_tdp_mmu_get_walk(vcpu, addr, sptes, &root);
        else
                leaf = get_walk(vcpu, addr, sptes, &root);

        walk_shadow_page_lockless_end(vcpu);

        if (unlikely(leaf < 0)) {
                *sptep = 0ull;
                return reserved;
        }

        *sptep = sptes[leaf];

        /*
         * Skip reserved bits checks on the terminal leaf if it's not a valid
         * SPTE.  Note, this also (intentionally) skips MMIO SPTEs, which, by
         * design, always have reserved bits set.  The purpose of the checks is
         * to detect reserved bits on non-MMIO SPTEs. i.e. buggy SPTEs.
         */
        if (!is_shadow_present_pte(sptes[leaf]))
                leaf++;

        rsvd_check = &vcpu->arch.mmu->shadow_zero_check;

        for (level = root; level >= leaf; level--)
                reserved |= is_rsvd_spte(rsvd_check, sptes[level], level);

        if (reserved) {
                pr_err("%s: reserved bits set on MMU-present spte, addr 0x%llx, hierarchy:\n",
                       __func__, addr);
                for (level = root; level >= leaf; level--)
                        pr_err("------ spte = 0x%llx level = %d, rsvd bits = 0x%llx",
                               sptes[level], level,
                               get_rsvd_bits(rsvd_check, sptes[level], level));
        }

        return reserved;
}

static int handle_mmio_page_fault(struct kvm_vcpu *vcpu, u64 addr, bool direct)
{
        u64 spte;
        bool reserved;

        if (mmio_info_in_cache(vcpu, addr, direct))
                return RET_PF_EMULATE;

        reserved = get_mmio_spte(vcpu, addr, &spte);
        if (WARN_ON(reserved))
                return -EINVAL;

        if (is_mmio_spte(spte)) {
                gfn_t gfn = get_mmio_spte_gfn(spte);
                unsigned int access = get_mmio_spte_access(spte);

                if (!check_mmio_spte(vcpu, spte))
                        return RET_PF_INVALID;

                if (direct)
                        addr = 0;

                trace_handle_mmio_page_fault(addr, gfn, access);
                vcpu_cache_mmio_info(vcpu, addr, gfn, access);
                return RET_PF_EMULATE;
        }

        /*
         * If the page table is zapped by other cpus, let CPU fault again on
         * the address.
         */
        return RET_PF_RETRY;
}

static bool page_fault_handle_page_track(struct kvm_vcpu *vcpu,
                                         struct kvm_page_fault *fault)
{
        if (unlikely(fault->rsvd))
                return false;

        if (!fault->present || !fault->write)
                return false;

        /*
         * guest is writing the page which is write tracked which can
         * not be fixed by page fault handler.
         */
        if (kvm_slot_page_track_is_active(vcpu->kvm, fault->slot, fault->gfn, KVM_PAGE_TRACK_WRITE))
                return true;

        return false;
}

static void shadow_page_table_clear_flood(struct kvm_vcpu *vcpu, gva_t addr)
{
        struct kvm_shadow_walk_iterator iterator;
        u64 spte;

        walk_shadow_page_lockless_begin(vcpu);
        for_each_shadow_entry_lockless(vcpu, addr, iterator, spte)
                clear_sp_write_flooding_count(iterator.sptep);
        walk_shadow_page_lockless_end(vcpu);
}

static u32 alloc_apf_token(struct kvm_vcpu *vcpu)
{
        /* make sure the token value is not 0 */
        u32 id = vcpu->arch.apf.id;

        if (id << 12 == 0)
                vcpu->arch.apf.id = 1;

        return (vcpu->arch.apf.id++ << 12) | vcpu->vcpu_id;
}

static bool kvm_arch_setup_async_pf(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa,
                                    gfn_t gfn)
{
        struct kvm_arch_async_pf arch;

        arch.token = alloc_apf_token(vcpu);
        arch.gfn = gfn;
        arch.direct_map = vcpu->arch.mmu->root_role.direct;
        arch.cr3 = vcpu->arch.mmu->get_guest_pgd(vcpu);

        return kvm_setup_async_pf(vcpu, cr2_or_gpa,
                                  kvm_vcpu_gfn_to_hva(vcpu, gfn), &arch);
}

void kvm_arch_async_page_ready(struct kvm_vcpu *vcpu, struct kvm_async_pf *work)
{
        int r;

        if ((vcpu->arch.mmu->root_role.direct != work->arch.direct_map) ||
              work->wakeup_all)
                return;

        r = kvm_mmu_reload(vcpu);
        if (unlikely(r))
                return;

        if (!vcpu->arch.mmu->root_role.direct &&
              work->arch.cr3 != vcpu->arch.mmu->get_guest_pgd(vcpu))
                return;

        kvm_mmu_do_page_fault(vcpu, work->cr2_or_gpa, 0, true);
}

static int __kvm_faultin_pfn(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault)
{
        struct kvm_memory_slot *slot = fault->slot;
        bool async;

        /*
         * Retry the page fault if the gfn hit a memslot that is being deleted
         * or moved.  This ensures any existing SPTEs for the old memslot will
         * be zapped before KVM inserts a new MMIO SPTE for the gfn.
         */
        if (slot && (slot->flags & KVM_MEMSLOT_INVALID))
                return RET_PF_RETRY;

        if (!kvm_is_visible_memslot(slot)) {
                /* Don't expose private memslots to L2. */
                if (is_guest_mode(vcpu)) {
                        fault->slot = NULL;
                        fault->pfn = KVM_PFN_NOSLOT;
                        fault->map_writable = false;
                        return RET_PF_CONTINUE;
                }
                /*
                 * If the APIC access page exists but is disabled, go directly
                 * to emulation without caching the MMIO access or creating a
                 * MMIO SPTE.  That way the cache doesn't need to be purged
                 * when the AVIC is re-enabled.
                 */
                if (slot && slot->id == APIC_ACCESS_PAGE_PRIVATE_MEMSLOT &&
                    !kvm_apicv_activated(vcpu->kvm))
                        return RET_PF_EMULATE;
        }

        async = false;
        fault->pfn = __gfn_to_pfn_memslot(slot, fault->gfn, false, false, &async,
                                          fault->write, &fault->map_writable,
                                          &fault->hva);
        if (!async)
                return RET_PF_CONTINUE; /* *pfn has correct page already */

        if (!fault->prefetch && kvm_can_do_async_pf(vcpu)) {
                trace_kvm_try_async_get_page(fault->addr, fault->gfn);
                if (kvm_find_async_pf_gfn(vcpu, fault->gfn)) {
                        trace_kvm_async_pf_repeated_fault(fault->addr, fault->gfn);
                        kvm_make_request(KVM_REQ_APF_HALT, vcpu);
                        return RET_PF_RETRY;
                } else if (kvm_arch_setup_async_pf(vcpu, fault->addr, fault->gfn)) {
                        return RET_PF_RETRY;
                }
        }

        /*
         * Allow gup to bail on pending non-fatal signals when it's also allowed
         * to wait for IO.  Note, gup always bails if it is unable to quickly
         * get a page and a fatal signal, i.e. SIGKILL, is pending.
         */
        fault->pfn = __gfn_to_pfn_memslot(slot, fault->gfn, false, true, NULL,
                                          fault->write, &fault->map_writable,
                                          &fault->hva);
        return RET_PF_CONTINUE;
}

static int kvm_faultin_pfn(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault,
                           unsigned int access)
{
        int ret;

        fault->mmu_seq = vcpu->kvm->mmu_invalidate_seq;
        smp_rmb();

        ret = __kvm_faultin_pfn(vcpu, fault);
        if (ret != RET_PF_CONTINUE)
                return ret;

        if (unlikely(is_error_pfn(fault->pfn)))
                return kvm_handle_error_pfn(vcpu, fault);

        if (unlikely(!fault->slot))
                return kvm_handle_noslot_fault(vcpu, fault, access);

        return RET_PF_CONTINUE;
}

/*
 * Returns true if the page fault is stale and needs to be retried, i.e. if the
 * root was invalidated by a memslot update or a relevant mmu_notifier fired.
 */
static bool is_page_fault_stale(struct kvm_vcpu *vcpu,
                                struct kvm_page_fault *fault)
{
        struct kvm_mmu_page *sp = to_shadow_page(vcpu->arch.mmu->root.hpa);

        /* Special roots, e.g. pae_root, are not backed by shadow pages. */
        if (sp && is_obsolete_sp(vcpu->kvm, sp))
                return true;

        /*
         * Roots without an associated shadow page are considered invalid if
         * there is a pending request to free obsolete roots.  The request is
         * only a hint that the current root _may_ be obsolete and needs to be
         * reloaded, e.g. if the guest frees a PGD that KVM is tracking as a
         * previous root, then __kvm_mmu_prepare_zap_page() signals all vCPUs
         * to reload even if no vCPU is actively using the root.
         */
        if (!sp && kvm_test_request(KVM_REQ_MMU_FREE_OBSOLETE_ROOTS, vcpu))
                return true;

        return fault->slot &&
               mmu_invalidate_retry_hva(vcpu->kvm, fault->mmu_seq, fault->hva);
}

static int direct_page_fault(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault)
{
        int r;

        if (page_fault_handle_page_track(vcpu, fault))
                return RET_PF_EMULATE;

        r = fast_page_fault(vcpu, fault);
        if (r != RET_PF_INVALID)
                return r;

        r = mmu_topup_memory_caches(vcpu, false);
        if (r)
                return r;

        r = kvm_faultin_pfn(vcpu, fault, ACC_ALL);
        if (r != RET_PF_CONTINUE)
                return r;

        r = RET_PF_RETRY;
        write_lock(&vcpu->kvm->mmu_lock);

        if (is_page_fault_stale(vcpu, fault))
                goto out_unlock;

        r = make_mmu_pages_available(vcpu);
        if (r)
                goto out_unlock;

        r = direct_map(vcpu, fault);

out_unlock:
        write_unlock(&vcpu->kvm->mmu_lock);
        kvm_release_pfn_clean(fault->pfn);
        return r;
}

static int nonpaging_page_fault(struct kvm_vcpu *vcpu,
                                struct kvm_page_fault *fault)
{
        pgprintk("%s: gva %lx error %x\n", __func__, fault->addr, fault->error_code);

        /* This path builds a PAE pagetable, we can map 2mb pages at maximum. */
        fault->max_level = PG_LEVEL_2M;
        return direct_page_fault(vcpu, fault);
}

int kvm_handle_page_fault(struct kvm_vcpu *vcpu, u64 error_code,
                                u64 fault_address, char *insn, int insn_len)
{
        int r = 1;
        u32 flags = vcpu->arch.apf.host_apf_flags;

#ifndef CONFIG_X86_64
        /* A 64-bit CR2 should be impossible on 32-bit KVM. */
        if (WARN_ON_ONCE(fault_address >> 32))
                return -EFAULT;
#endif

        vcpu->arch.l1tf_flush_l1d = true;
        if (!flags) {
                trace_kvm_page_fault(vcpu, fault_address, error_code);

                if (kvm_event_needs_reinjection(vcpu))
                        kvm_mmu_unprotect_page_virt(vcpu, fault_address);
                r = kvm_mmu_page_fault(vcpu, fault_address, error_code, insn,
                                insn_len);
        } else if (flags & KVM_PV_REASON_PAGE_NOT_PRESENT) {
                vcpu->arch.apf.host_apf_flags = 0;
                local_irq_disable();
                kvm_async_pf_task_wait_schedule(fault_address);
                local_irq_enable();
        } else {
                WARN_ONCE(1, "Unexpected host async PF flags: %x\n", flags);
        }

        return r;
}
EXPORT_SYMBOL_GPL(kvm_handle_page_fault);

#ifdef CONFIG_X86_64
static int kvm_tdp_mmu_page_fault(struct kvm_vcpu *vcpu,
                                  struct kvm_page_fault *fault)
{
        int r;

        if (page_fault_handle_page_track(vcpu, fault))
                return RET_PF_EMULATE;

        r = fast_page_fault(vcpu, fault);
        if (r != RET_PF_INVALID)
                return r;

        r = mmu_topup_memory_caches(vcpu, false);
        if (r)
                return r;

        r = kvm_faultin_pfn(vcpu, fault, ACC_ALL);
        if (r != RET_PF_CONTINUE)
                return r;

        r = RET_PF_RETRY;
        read_lock(&vcpu->kvm->mmu_lock);

        if (is_page_fault_stale(vcpu, fault))
                goto out_unlock;

        r = kvm_tdp_mmu_map(vcpu, fault);

out_unlock:
        read_unlock(&vcpu->kvm->mmu_lock);
        kvm_release_pfn_clean(fault->pfn);
        return r;
}
#endif

int kvm_tdp_page_fault(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault)
{
        /*
         * If the guest's MTRRs may be used to compute the "real" memtype,
         * restrict the mapping level to ensure KVM uses a consistent memtype
         * across the entire mapping.  If the host MTRRs are ignored by TDP
         * (shadow_memtype_mask is non-zero), and the VM has non-coherent DMA
         * (DMA doesn't snoop CPU caches), KVM's ABI is to honor the memtype
         * from the guest's MTRRs so that guest accesses to memory that is
         * DMA'd aren't cached against the guest's wishes.
         *
         * Note, KVM may still ultimately ignore guest MTRRs for certain PFNs,
         * e.g. KVM will force UC memtype for host MMIO.
         */
        if (shadow_memtype_mask && kvm_arch_has_noncoherent_dma(vcpu->kvm)) {
                for ( ; fault->max_level > PG_LEVEL_4K; --fault->max_level) {
                        int page_num = KVM_PAGES_PER_HPAGE(fault->max_level);
                        gfn_t base = fault->gfn & ~(page_num - 1);

                        if (kvm_mtrr_check_gfn_range_consistency(vcpu, base, page_num))
                                break;
                }
        }

#ifdef CONFIG_X86_64
        if (tdp_mmu_enabled)
                return kvm_tdp_mmu_page_fault(vcpu, fault);
#endif

        return direct_page_fault(vcpu, fault);
}

static void nonpaging_init_context(struct kvm_mmu *context)
{
        context->page_fault = nonpaging_page_fault;
        context->gva_to_gpa = nonpaging_gva_to_gpa;
        context->sync_page = nonpaging_sync_page;
        context->invlpg = NULL;
}

static inline bool is_root_usable(struct kvm_mmu_root_info *root, gpa_t pgd,
                                  union kvm_mmu_page_role role)
{
        return (role.direct || pgd == root->pgd) &&
               VALID_PAGE(root->hpa) &&
               role.word == to_shadow_page(root->hpa)->role.word;
}

/*
 * Find out if a previously cached root matching the new pgd/role is available,
 * and insert the current root as the MRU in the cache.
 * If a matching root is found, it is assigned to kvm_mmu->root and
 * true is returned.
 * If no match is found, kvm_mmu->root is left invalid, the LRU root is
 * evicted to make room for the current root, and false is returned.
 */
static bool cached_root_find_and_keep_current(struct kvm *kvm, struct kvm_mmu *mmu,
                                              gpa_t new_pgd,
                                              union kvm_mmu_page_role new_role)
{
        uint i;

        if (is_root_usable(&mmu->root, new_pgd, new_role))
                return true;

        for (i = 0; i < KVM_MMU_NUM_PREV_ROOTS; i++) {
                /*
                 * The swaps end up rotating the cache like this:
                 *   C   0 1 2 3   (on entry to the function)
                 *   0   C 1 2 3
                 *   1   C 0 2 3
                 *   2   C 0 1 3
                 *   3   C 0 1 2   (on exit from the loop)
                 */
                swap(mmu->root, mmu->prev_roots[i]);
                if (is_root_usable(&mmu->root, new_pgd, new_role))
                        return true;
        }

        kvm_mmu_free_roots(kvm, mmu, KVM_MMU_ROOT_CURRENT);
        return false;
}

/*
 * Find out if a previously cached root matching the new pgd/role is available.
 * On entry, mmu->root is invalid.
 * If a matching root is found, it is assigned to kvm_mmu->root, the LRU entry
 * of the cache becomes invalid, and true is returned.
 * If no match is found, kvm_mmu->root is left invalid and false is returned.
 */
static bool cached_root_find_without_current(struct kvm *kvm, struct kvm_mmu *mmu,
                                             gpa_t new_pgd,
                                             union kvm_mmu_page_role new_role)
{
        uint i;

        for (i = 0; i < KVM_MMU_NUM_PREV_ROOTS; i++)
                if (is_root_usable(&mmu->prev_roots[i], new_pgd, new_role))
                        goto hit;

        return false;

hit:
        swap(mmu->root, mmu->prev_roots[i]);
        /* Bubble up the remaining roots.  */
        for (; i < KVM_MMU_NUM_PREV_ROOTS - 1; i++)
                mmu->prev_roots[i] = mmu->prev_roots[i + 1];
        mmu->prev_roots[i].hpa = INVALID_PAGE;
        return true;
}

static bool fast_pgd_switch(struct kvm *kvm, struct kvm_mmu *mmu,
                            gpa_t new_pgd, union kvm_mmu_page_role new_role)
{
        /*
         * For now, limit the caching to 64-bit hosts+VMs in order to avoid
         * having to deal with PDPTEs. We may add support for 32-bit hosts/VMs
         * later if necessary.
         */
        if (VALID_PAGE(mmu->root.hpa) && !to_shadow_page(mmu->root.hpa))
                kvm_mmu_free_roots(kvm, mmu, KVM_MMU_ROOT_CURRENT);

        if (VALID_PAGE(mmu->root.hpa))
                return cached_root_find_and_keep_current(kvm, mmu, new_pgd, new_role);
        else
                return cached_root_find_without_current(kvm, mmu, new_pgd, new_role);
}

void kvm_mmu_new_pgd(struct kvm_vcpu *vcpu, gpa_t new_pgd)
{
        struct kvm_mmu *mmu = vcpu->arch.mmu;
        union kvm_mmu_page_role new_role = mmu->root_role;

        if (!fast_pgd_switch(vcpu->kvm, mmu, new_pgd, new_role)) {
                /* kvm_mmu_ensure_valid_pgd will set up a new root.  */
                return;
        }

        /*
         * It's possible that the cached previous root page is obsolete because
         * of a change in the MMU generation number. However, changing the
         * generation number is accompanied by KVM_REQ_MMU_FREE_OBSOLETE_ROOTS,
         * which will free the root set here and allocate a new one.
         */
        kvm_make_request(KVM_REQ_LOAD_MMU_PGD, vcpu);

        if (force_flush_and_sync_on_reuse) {
                kvm_make_request(KVM_REQ_MMU_SYNC, vcpu);
                kvm_make_request(KVM_REQ_TLB_FLUSH_CURRENT, vcpu);
        }

        /*
         * The last MMIO access's GVA and GPA are cached in the VCPU. When
         * switching to a new CR3, that GVA->GPA mapping may no longer be
         * valid. So clear any cached MMIO info even when we don't need to sync
         * the shadow page tables.
         */
        vcpu_clear_mmio_info(vcpu, MMIO_GVA_ANY);

        /*
         * If this is a direct root page, it doesn't have a write flooding
         * count. Otherwise, clear the write flooding count.
         */
        if (!new_role.direct)
                __clear_sp_write_flooding_count(
                                to_shadow_page(vcpu->arch.mmu->root.hpa));
}
EXPORT_SYMBOL_GPL(kvm_mmu_new_pgd);

static unsigned long get_cr3(struct kvm_vcpu *vcpu)
{
        return kvm_read_cr3(vcpu);
}

static bool sync_mmio_spte(struct kvm_vcpu *vcpu, u64 *sptep, gfn_t gfn,
                           unsigned int access)
{
        if (unlikely(is_mmio_spte(*sptep))) {
                if (gfn != get_mmio_spte_gfn(*sptep)) {
                        mmu_spte_clear_no_track(sptep);
                        return true;
                }

                mark_mmio_spte(vcpu, sptep, gfn, access);
                return true;
        }

        return false;
}

#define PTTYPE_EPT 18 /* arbitrary */
#define PTTYPE PTTYPE_EPT
#include "paging_tmpl.h"
#undef PTTYPE

#define PTTYPE 64
#include "paging_tmpl.h"
#undef PTTYPE

#define PTTYPE 32
#include "paging_tmpl.h"
#undef PTTYPE

static void
__reset_rsvds_bits_mask(struct rsvd_bits_validate *rsvd_check,
                        u64 pa_bits_rsvd, int level, bool nx, bool gbpages,
                        bool pse, bool amd)
{
        u64 gbpages_bit_rsvd = 0;
        u64 nonleaf_bit8_rsvd = 0;
        u64 high_bits_rsvd;

        rsvd_check->bad_mt_xwr = 0;

        if (!gbpages)
                gbpages_bit_rsvd = rsvd_bits(7, 7);

        if (level == PT32E_ROOT_LEVEL)
                high_bits_rsvd = pa_bits_rsvd & rsvd_bits(0, 62);
        else
                high_bits_rsvd = pa_bits_rsvd & rsvd_bits(0, 51);

        /* Note, NX doesn't exist in PDPTEs, this is handled below. */
        if (!nx)
                high_bits_rsvd |= rsvd_bits(63, 63);

        /*
         * Non-leaf PML4Es and PDPEs reserve bit 8 (which would be the G bit for
         * leaf entries) on AMD CPUs only.
         */
        if (amd)
                nonleaf_bit8_rsvd = rsvd_bits(8, 8);

        switch (level) {
        case PT32_ROOT_LEVEL:
                /* no rsvd bits for 2 level 4K page table entries */
                rsvd_check->rsvd_bits_mask[0][1] = 0;
                rsvd_check->rsvd_bits_mask[0][0] = 0;
                rsvd_check->rsvd_bits_mask[1][0] =
                        rsvd_check->rsvd_bits_mask[0][0];

                if (!pse) {
                        rsvd_check->rsvd_bits_mask[1][1] = 0;
                        break;
                }

                if (is_cpuid_PSE36())
                        /* 36bits PSE 4MB page */
                        rsvd_check->rsvd_bits_mask[1][1] = rsvd_bits(17, 21);
                else
                        /* 32 bits PSE 4MB page */
                        rsvd_check->rsvd_bits_mask[1][1] = rsvd_bits(13, 21);
                break;
        case PT32E_ROOT_LEVEL:
                rsvd_check->rsvd_bits_mask[0][2] = rsvd_bits(63, 63) |
                                                   high_bits_rsvd |
                                                   rsvd_bits(5, 8) |
                                                   rsvd_bits(1, 2);     /* PDPTE */
                rsvd_check->rsvd_bits_mask[0][1] = high_bits_rsvd;      /* PDE */
                rsvd_check->rsvd_bits_mask[0][0] = high_bits_rsvd;      /* PTE */
                rsvd_check->rsvd_bits_mask[1][1] = high_bits_rsvd |
                                                   rsvd_bits(13, 20);   /* large page */
                rsvd_check->rsvd_bits_mask[1][0] =
                        rsvd_check->rsvd_bits_mask[0][0];
                break;
        case PT64_ROOT_5LEVEL:
                rsvd_check->rsvd_bits_mask[0][4] = high_bits_rsvd |
                                                   nonleaf_bit8_rsvd |
                                                   rsvd_bits(7, 7);
                rsvd_check->rsvd_bits_mask[1][4] =
                        rsvd_check->rsvd_bits_mask[0][4];
                fallthrough;
        case PT64_ROOT_4LEVEL:
                rsvd_check->rsvd_bits_mask[0][3] = high_bits_rsvd |
                                                   nonleaf_bit8_rsvd |
                                                   rsvd_bits(7, 7);
                rsvd_check->rsvd_bits_mask[0][2] = high_bits_rsvd |
                                                   gbpages_bit_rsvd;
                rsvd_check->rsvd_bits_mask[0][1] = high_bits_rsvd;
                rsvd_check->rsvd_bits_mask[0][0] = high_bits_rsvd;
                rsvd_check->rsvd_bits_mask[1][3] =
                        rsvd_check->rsvd_bits_mask[0][3];
                rsvd_check->rsvd_bits_mask[1][2] = high_bits_rsvd |
                                                   gbpages_bit_rsvd |
                                                   rsvd_bits(13, 29);
                rsvd_check->rsvd_bits_mask[1][1] = high_bits_rsvd |
                                                   rsvd_bits(13, 20); /* large page */
                rsvd_check->rsvd_bits_mask[1][0] =
                        rsvd_check->rsvd_bits_mask[0][0];
                break;
        }
}

static bool guest_can_use_gbpages(struct kvm_vcpu *vcpu)
{
        /*
         * If TDP is enabled, let the guest use GBPAGES if they're supported in
         * hardware.  The hardware page walker doesn't let KVM disable GBPAGES,
         * i.e. won't treat them as reserved, and KVM doesn't redo the GVA->GPA
         * walk for performance and complexity reasons.  Not to mention KVM
         * _can't_ solve the problem because GVA->GPA walks aren't visible to
         * KVM once a TDP translation is installed.  Mimic hardware behavior so
         * that KVM's is at least consistent, i.e. doesn't randomly inject #PF.
         */
        return tdp_enabled ? boot_cpu_has(X86_FEATURE_GBPAGES) :
                             guest_cpuid_has(vcpu, X86_FEATURE_GBPAGES);
}

static void reset_guest_rsvds_bits_mask(struct kvm_vcpu *vcpu,
                                        struct kvm_mmu *context)
{
        __reset_rsvds_bits_mask(&context->guest_rsvd_check,
                                vcpu->arch.reserved_gpa_bits,
                                context->cpu_role.base.level, is_efer_nx(context),
                                guest_can_use_gbpages(vcpu),
                                is_cr4_pse(context),
                                guest_cpuid_is_amd_or_hygon(vcpu));
}

static void
__reset_rsvds_bits_mask_ept(struct rsvd_bits_validate *rsvd_check,
                            u64 pa_bits_rsvd, bool execonly, int huge_page_level)
{
        u64 high_bits_rsvd = pa_bits_rsvd & rsvd_bits(0, 51);
        u64 large_1g_rsvd = 0, large_2m_rsvd = 0;
        u64 bad_mt_xwr;

        if (huge_page_level < PG_LEVEL_1G)
                large_1g_rsvd = rsvd_bits(7, 7);
        if (huge_page_level < PG_LEVEL_2M)
                large_2m_rsvd = rsvd_bits(7, 7);

        rsvd_check->rsvd_bits_mask[0][4] = high_bits_rsvd | rsvd_bits(3, 7);
        rsvd_check->rsvd_bits_mask[0][3] = high_bits_rsvd | rsvd_bits(3, 7);
        rsvd_check->rsvd_bits_mask[0][2] = high_bits_rsvd | rsvd_bits(3, 6) | large_1g_rsvd;
        rsvd_check->rsvd_bits_mask[0][1] = high_bits_rsvd | rsvd_bits(3, 6) | large_2m_rsvd;
        rsvd_check->rsvd_bits_mask[0][0] = high_bits_rsvd;

        /* large page */
        rsvd_check->rsvd_bits_mask[1][4] = rsvd_check->rsvd_bits_mask[0][4];
        rsvd_check->rsvd_bits_mask[1][3] = rsvd_check->rsvd_bits_mask[0][3];
        rsvd_check->rsvd_bits_mask[1][2] = high_bits_rsvd | rsvd_bits(12, 29) | large_1g_rsvd;
        rsvd_check->rsvd_bits_mask[1][1] = high_bits_rsvd | rsvd_bits(12, 20) | large_2m_rsvd;
        rsvd_check->rsvd_bits_mask[1][0] = rsvd_check->rsvd_bits_mask[0][0];

        bad_mt_xwr = 0xFFull << (2 * 8);        /* bits 3..5 must not be 2 */
        bad_mt_xwr |= 0xFFull << (3 * 8);       /* bits 3..5 must not be 3 */
        bad_mt_xwr |= 0xFFull << (7 * 8);       /* bits 3..5 must not be 7 */
        bad_mt_xwr |= REPEAT_BYTE(1ull << 2);   /* bits 0..2 must not be 010 */
        bad_mt_xwr |= REPEAT_BYTE(1ull << 6);   /* bits 0..2 must not be 110 */
        if (!execonly) {
                /* bits 0..2 must not be 100 unless VMX capabilities allow it */
                bad_mt_xwr |= REPEAT_BYTE(1ull << 4);
        }
        rsvd_check->bad_mt_xwr = bad_mt_xwr;
}

static void reset_rsvds_bits_mask_ept(struct kvm_vcpu *vcpu,
                struct kvm_mmu *context, bool execonly, int huge_page_level)
{
        __reset_rsvds_bits_mask_ept(&context->guest_rsvd_check,
                                    vcpu->arch.reserved_gpa_bits, execonly,
                                    huge_page_level);
}

static inline u64 reserved_hpa_bits(void)
{
        return rsvd_bits(shadow_phys_bits, 63);
}

/*
 * the page table on host is the shadow page table for the page
 * table in guest or amd nested guest, its mmu features completely
 * follow the features in guest.
 */
static void reset_shadow_zero_bits_mask(struct kvm_vcpu *vcpu,
                                        struct kvm_mmu *context)
{
        /* @amd adds a check on bit of SPTEs, which KVM shouldn't use anyways. */
        bool is_amd = true;
        /* KVM doesn't use 2-level page tables for the shadow MMU. */
        bool is_pse = false;
        struct rsvd_bits_validate *shadow_zero_check;
        int i;

        WARN_ON_ONCE(context->root_role.level < PT32E_ROOT_LEVEL);

        shadow_zero_check = &context->shadow_zero_check;
        __reset_rsvds_bits_mask(shadow_zero_check, reserved_hpa_bits(),
                                context->root_role.level,
                                context->root_role.efer_nx,
                                guest_can_use_gbpages(vcpu), is_pse, is_amd);

        if (!shadow_me_mask)
                return;

        for (i = context->root_role.level; --i >= 0;) {
                /*
                 * So far shadow_me_value is a constant during KVM's life
                 * time.  Bits in shadow_me_value are allowed to be set.
                 * Bits in shadow_me_mask but not in shadow_me_value are
                 * not allowed to be set.
                 */
                shadow_zero_check->rsvd_bits_mask[0][i] |= shadow_me_mask;
                shadow_zero_check->rsvd_bits_mask[1][i] |= shadow_me_mask;
                shadow_zero_check->rsvd_bits_mask[0][i] &= ~shadow_me_value;
                shadow_zero_check->rsvd_bits_mask[1][i] &= ~shadow_me_value;
        }

}

static inline bool boot_cpu_is_amd(void)
{
        WARN_ON_ONCE(!tdp_enabled);
        return shadow_x_mask == 0;
}

/*
 * the direct page table on host, use as much mmu features as
 * possible, however, kvm currently does not do execution-protection.
 */
static void
reset_tdp_shadow_zero_bits_mask(struct kvm_mmu *context)
{
        struct rsvd_bits_validate *shadow_zero_check;
        int i;

        shadow_zero_check = &context->shadow_zero_check;

        if (boot_cpu_is_amd())
                __reset_rsvds_bits_mask(shadow_zero_check, reserved_hpa_bits(),
                                        context->root_role.level, true,
                                        boot_cpu_has(X86_FEATURE_GBPAGES),
                                        false, true);
        else
                __reset_rsvds_bits_mask_ept(shadow_zero_check,
                                            reserved_hpa_bits(), false,
                                            max_huge_page_level);

        if (!shadow_me_mask)
                return;

        for (i = context->root_role.level; --i >= 0;) {
                shadow_zero_check->rsvd_bits_mask[0][i] &= ~shadow_me_mask;
                shadow_zero_check->rsvd_bits_mask[1][i] &= ~shadow_me_mask;
        }
}

/*
 * as the comments in reset_shadow_zero_bits_mask() except it
 * is the shadow page table for intel nested guest.
 */
static void
reset_ept_shadow_zero_bits_mask(struct kvm_mmu *context, bool execonly)
{
        __reset_rsvds_bits_mask_ept(&context->shadow_zero_check,
                                    reserved_hpa_bits(), execonly,
                                    max_huge_page_level);
}

#define BYTE_MASK(access) \
        ((1 & (access) ? 2 : 0) | \
         (2 & (access) ? 4 : 0) | \
         (3 & (access) ? 8 : 0) | \
         (4 & (access) ? 16 : 0) | \
         (5 & (access) ? 32 : 0) | \
         (6 & (access) ? 64 : 0) | \
         (7 & (access) ? 128 : 0))


static void update_permission_bitmask(struct kvm_mmu *mmu, bool ept)
{
        unsigned byte;

        const u8 x = BYTE_MASK(ACC_EXEC_MASK);
        const u8 w = BYTE_MASK(ACC_WRITE_MASK);
        const u8 u = BYTE_MASK(ACC_USER_MASK);

        bool cr4_smep = is_cr4_smep(mmu);
        bool cr4_smap = is_cr4_smap(mmu);
        bool cr0_wp = is_cr0_wp(mmu);
        bool efer_nx = is_efer_nx(mmu);

        for (byte = 0; byte < ARRAY_SIZE(mmu->permissions); ++byte) {
                unsigned pfec = byte << 1;

                /*
                 * Each "*f" variable has a 1 bit for each UWX value
                 * that causes a fault with the given PFEC.
                 */

                /* Faults from writes to non-writable pages */
                u8 wf = (pfec & PFERR_WRITE_MASK) ? (u8)~w : 0;
                /* Faults from user mode accesses to supervisor pages */
                u8 uf = (pfec & PFERR_USER_MASK) ? (u8)~u : 0;
                /* Faults from fetches of non-executable pages*/
                u8 ff = (pfec & PFERR_FETCH_MASK) ? (u8)~x : 0;
                /* Faults from kernel mode fetches of user pages */
                u8 smepf = 0;
                /* Faults from kernel mode accesses of user pages */
                u8 smapf = 0;

                if (!ept) {
                        /* Faults from kernel mode accesses to user pages */
                        u8 kf = (pfec & PFERR_USER_MASK) ? 0 : u;

                        /* Not really needed: !nx will cause pte.nx to fault */
                        if (!efer_nx)
                                ff = 0;

                        /* Allow supervisor writes if !cr0.wp */
                        if (!cr0_wp)
                                wf = (pfec & PFERR_USER_MASK) ? wf : 0;

                        /* Disallow supervisor fetches of user code if cr4.smep */
                        if (cr4_smep)
                                smepf = (pfec & PFERR_FETCH_MASK) ? kf : 0;

                        /*
                         * SMAP:kernel-mode data accesses from user-mode
                         * mappings should fault. A fault is considered
                         * as a SMAP violation if all of the following
                         * conditions are true:
                         *   - X86_CR4_SMAP is set in CR4
                         *   - A user page is accessed
                         *   - The access is not a fetch
                         *   - The access is supervisor mode
                         *   - If implicit supervisor access or X86_EFLAGS_AC is clear
                         *
                         * Here, we cover the first four conditions.
                         * The fifth is computed dynamically in permission_fault();
                         * PFERR_RSVD_MASK bit will be set in PFEC if the access is
                         * *not* subject to SMAP restrictions.
                         */
                        if (cr4_smap)
                                smapf = (pfec & (PFERR_RSVD_MASK|PFERR_FETCH_MASK)) ? 0 : kf;
                }

                mmu->permissions[byte] = ff | uf | wf | smepf | smapf;
        }
}

/*
* PKU is an additional mechanism by which the paging controls access to
* user-mode addresses based on the value in the PKRU register.  Protection
* key violations are reported through a bit in the page fault error code.
* Unlike other bits of the error code, the PK bit is not known at the
* call site of e.g. gva_to_gpa; it must be computed directly in
* permission_fault based on two bits of PKRU, on some machine state (CR4,
* CR0, EFER, CPL), and on other bits of the error code and the page tables.
*
* In particular the following conditions come from the error code, the
* page tables and the machine state:
* - PK is always zero unless CR4.PKE=1 and EFER.LMA=1
* - PK is always zero if RSVD=1 (reserved bit set) or F=1 (instruction fetch)
* - PK is always zero if U=0 in the page tables
* - PKRU.WD is ignored if CR0.WP=0 and the access is a supervisor access.
*
* The PKRU bitmask caches the result of these four conditions.  The error
* code (minus the P bit) and the page table's U bit form an index into the
* PKRU bitmask.  Two bits of the PKRU bitmask are then extracted and ANDed
* with the two bits of the PKRU register corresponding to the protection key.
* For the first three conditions above the bits will be 00, thus masking
* away both AD and WD.  For all reads or if the last condition holds, WD
* only will be masked away.
*/
static void update_pkru_bitmask(struct kvm_mmu *mmu)
{
        unsigned bit;
        bool wp;

        mmu->pkru_mask = 0;

        if (!is_cr4_pke(mmu))
                return;

        wp = is_cr0_wp(mmu);

        for (bit = 0; bit < ARRAY_SIZE(mmu->permissions); ++bit) {
                unsigned pfec, pkey_bits;
                bool check_pkey, check_write, ff, uf, wf, pte_user;

                pfec = bit << 1;
                ff = pfec & PFERR_FETCH_MASK;
                uf = pfec & PFERR_USER_MASK;
                wf = pfec & PFERR_WRITE_MASK;

                /* PFEC.RSVD is replaced by ACC_USER_MASK. */
                pte_user = pfec & PFERR_RSVD_MASK;

                /*
                 * Only need to check the access which is not an
                 * instruction fetch and is to a user page.
                 */
                check_pkey = (!ff && pte_user);
                /*
                 * write access is controlled by PKRU if it is a
                 * user access or CR0.WP = 1.
                 */
                check_write = check_pkey && wf && (uf || wp);

                /* PKRU.AD stops both read and write access. */
                pkey_bits = !!check_pkey;
                /* PKRU.WD stops write access. */
                pkey_bits |= (!!check_write) << 1;

                mmu->pkru_mask |= (pkey_bits & 3) << pfec;
        }
}

static void reset_guest_paging_metadata(struct kvm_vcpu *vcpu,
                                        struct kvm_mmu *mmu)
{
        if (!is_cr0_pg(mmu))
                return;

        reset_guest_rsvds_bits_mask(vcpu, mmu);
        update_permission_bitmask(mmu, false);
        update_pkru_bitmask(mmu);
}

static void paging64_init_context(struct kvm_mmu *context)
{
        context->page_fault = paging64_page_fault;
        context->gva_to_gpa = paging64_gva_to_gpa;
        context->sync_page = paging64_sync_page;
        context->invlpg = paging64_invlpg;
}

static void paging32_init_context(struct kvm_mmu *context)
{
        context->page_fault = paging32_page_fault;
        context->gva_to_gpa = paging32_gva_to_gpa;
        context->sync_page = paging32_sync_page;
        context->invlpg = paging32_invlpg;
}

static union kvm_cpu_role
kvm_calc_cpu_role(struct kvm_vcpu *vcpu, const struct kvm_mmu_role_regs *regs)
{
        union kvm_cpu_role role = {0};

        role.base.access = ACC_ALL;
        role.base.smm = is_smm(vcpu);
        role.base.guest_mode = is_guest_mode(vcpu);
        role.ext.valid = 1;

        if (!____is_cr0_pg(regs)) {
                role.base.direct = 1;
                return role;
        }

        role.base.efer_nx = ____is_efer_nx(regs);
        role.base.cr0_wp = ____is_cr0_wp(regs);
        role.base.smep_andnot_wp = ____is_cr4_smep(regs) && !____is_cr0_wp(regs);
        role.base.smap_andnot_wp = ____is_cr4_smap(regs) && !____is_cr0_wp(regs);
        role.base.has_4_byte_gpte = !____is_cr4_pae(regs);

        if (____is_efer_lma(regs))
                role.base.level = ____is_cr4_la57(regs) ? PT64_ROOT_5LEVEL
                                                        : PT64_ROOT_4LEVEL;
        else if (____is_cr4_pae(regs))
                role.base.level = PT32E_ROOT_LEVEL;
        else
                role.base.level = PT32_ROOT_LEVEL;

        role.ext.cr4_smep = ____is_cr4_smep(regs);
        role.ext.cr4_smap = ____is_cr4_smap(regs);
        role.ext.cr4_pse = ____is_cr4_pse(regs);

        /* PKEY and LA57 are active iff long mode is active. */
        role.ext.cr4_pke = ____is_efer_lma(regs) && ____is_cr4_pke(regs);
        role.ext.cr4_la57 = ____is_efer_lma(regs) && ____is_cr4_la57(regs);
        role.ext.efer_lma = ____is_efer_lma(regs);
        return role;
}

static inline int kvm_mmu_get_tdp_level(struct kvm_vcpu *vcpu)
{
        /* tdp_root_level is architecture forced level, use it if nonzero */
        if (tdp_root_level)
                return tdp_root_level;

        /* Use 5-level TDP if and only if it's useful/necessary. */
        if (max_tdp_level == 5 && cpuid_maxphyaddr(vcpu) <= 48)
                return 4;

        return max_tdp_level;
}

static union kvm_mmu_page_role
kvm_calc_tdp_mmu_root_page_role(struct kvm_vcpu *vcpu,
                                union kvm_cpu_role cpu_role)
{
        union kvm_mmu_page_role role = {0};

        role.access = ACC_ALL;
        role.cr0_wp = true;
        role.efer_nx = true;
        role.smm = cpu_role.base.smm;
        role.guest_mode = cpu_role.base.guest_mode;
        role.ad_disabled = !kvm_ad_enabled();
        role.level = kvm_mmu_get_tdp_level(vcpu);
        role.direct = true;
        role.has_4_byte_gpte = false;

        return role;
}

static void init_kvm_tdp_mmu(struct kvm_vcpu *vcpu,
                             union kvm_cpu_role cpu_role)
{
        struct kvm_mmu *context = &vcpu->arch.root_mmu;
        union kvm_mmu_page_role root_role = kvm_calc_tdp_mmu_root_page_role(vcpu, cpu_role);

        if (cpu_role.as_u64 == context->cpu_role.as_u64 &&
            root_role.word == context->root_role.word)
                return;

        context->cpu_role.as_u64 = cpu_role.as_u64;
        context->root_role.word = root_role.word;
        context->page_fault = kvm_tdp_page_fault;
        context->sync_page = nonpaging_sync_page;
        context->invlpg = NULL;
        context->get_guest_pgd = get_cr3;
        context->get_pdptr = kvm_pdptr_read;
        context->inject_page_fault = kvm_inject_page_fault;

        if (!is_cr0_pg(context))
                context->gva_to_gpa = nonpaging_gva_to_gpa;
        else if (is_cr4_pae(context))
                context->gva_to_gpa = paging64_gva_to_gpa;
        else
                context->gva_to_gpa = paging32_gva_to_gpa;

        reset_guest_paging_metadata(vcpu, context);
        reset_tdp_shadow_zero_bits_mask(context);
}

static void shadow_mmu_init_context(struct kvm_vcpu *vcpu, struct kvm_mmu *context,
                                    union kvm_cpu_role cpu_role,
                                    union kvm_mmu_page_role root_role)
{
        if (cpu_role.as_u64 == context->cpu_role.as_u64 &&
            root_role.word == context->root_role.word)
                return;

        context->cpu_role.as_u64 = cpu_role.as_u64;
        context->root_role.word = root_role.word;

        if (!is_cr0_pg(context))
                nonpaging_init_context(context);
        else if (is_cr4_pae(context))
                paging64_init_context(context);
        else
                paging32_init_context(context);

        reset_guest_paging_metadata(vcpu, context);
        reset_shadow_zero_bits_mask(vcpu, context);
}

static void kvm_init_shadow_mmu(struct kvm_vcpu *vcpu,
                                union kvm_cpu_role cpu_role)
{
        struct kvm_mmu *context = &vcpu->arch.root_mmu;
        union kvm_mmu_page_role root_role;

        root_role = cpu_role.base;

        /* KVM uses PAE paging whenever the guest isn't using 64-bit paging. */
        root_role.level = max_t(u32, root_role.level, PT32E_ROOT_LEVEL);

        /*
         * KVM forces EFER.NX=1 when TDP is disabled, reflect it in the MMU role.
         * KVM uses NX when TDP is disabled to handle a variety of scenarios,
         * notably for huge SPTEs if iTLB multi-hit mitigation is enabled and
         * to generate correct permissions for CR0.WP=0/CR4.SMEP=1/EFER.NX=0.
         * The iTLB multi-hit workaround can be toggled at any time, so assume
         * NX can be used by any non-nested shadow MMU to avoid having to reset
         * MMU contexts.
         */
        root_role.efer_nx = true;

        shadow_mmu_init_context(vcpu, context, cpu_role, root_role);
}

void kvm_init_shadow_npt_mmu(struct kvm_vcpu *vcpu, unsigned long cr0,
                             unsigned long cr4, u64 efer, gpa_t nested_cr3)
{
        struct kvm_mmu *context = &vcpu->arch.guest_mmu;
        struct kvm_mmu_role_regs regs = {
                .cr0 = cr0,
                .cr4 = cr4 & ~X86_CR4_PKE,
                .efer = efer,
        };
        union kvm_cpu_role cpu_role = kvm_calc_cpu_role(vcpu, &regs);
        union kvm_mmu_page_role root_role;

        /* NPT requires CR0.PG=1. */
        WARN_ON_ONCE(cpu_role.base.direct);

        root_role = cpu_role.base;
        root_role.level = kvm_mmu_get_tdp_level(vcpu);
        if (root_role.level == PT64_ROOT_5LEVEL &&
            cpu_role.base.level == PT64_ROOT_4LEVEL)
                root_role.passthrough = 1;

        shadow_mmu_init_context(vcpu, context, cpu_role, root_role);
        kvm_mmu_new_pgd(vcpu, nested_cr3);
}
EXPORT_SYMBOL_GPL(kvm_init_shadow_npt_mmu);

static union kvm_cpu_role
kvm_calc_shadow_ept_root_page_role(struct kvm_vcpu *vcpu, bool accessed_dirty,
                                   bool execonly, u8 level)
{
        union kvm_cpu_role role = {0};

        /*
         * KVM does not support SMM transfer monitors, and consequently does not
         * support the "entry to SMM" control either.  role.base.smm is always 0.
         */
        WARN_ON_ONCE(is_smm(vcpu));
        role.base.level = level;
        role.base.has_4_byte_gpte = false;
        role.base.direct = false;
        role.base.ad_disabled = !accessed_dirty;
        role.base.guest_mode = true;
        role.base.access = ACC_ALL;

        role.ext.word = 0;
        role.ext.execonly = execonly;
        role.ext.valid = 1;

        return role;
}

void kvm_init_shadow_ept_mmu(struct kvm_vcpu *vcpu, bool execonly,
                             int huge_page_level, bool accessed_dirty,
                             gpa_t new_eptp)
{
        struct kvm_mmu *context = &vcpu->arch.guest_mmu;
        u8 level = vmx_eptp_page_walk_level(new_eptp);
        union kvm_cpu_role new_mode =
                kvm_calc_shadow_ept_root_page_role(vcpu, accessed_dirty,
                                                   execonly, level);

        if (new_mode.as_u64 != context->cpu_role.as_u64) {
                /* EPT, and thus nested EPT, does not consume CR0, CR4, nor EFER. */
                context->cpu_role.as_u64 = new_mode.as_u64;
                context->root_role.word = new_mode.base.word;

                context->page_fault = ept_page_fault;
                context->gva_to_gpa = ept_gva_to_gpa;
                context->sync_page = ept_sync_page;
                context->invlpg = ept_invlpg;

                update_permission_bitmask(context, true);
                context->pkru_mask = 0;
                reset_rsvds_bits_mask_ept(vcpu, context, execonly, huge_page_level);
                reset_ept_shadow_zero_bits_mask(context, execonly);
        }

        kvm_mmu_new_pgd(vcpu, new_eptp);
}
EXPORT_SYMBOL_GPL(kvm_init_shadow_ept_mmu);

static void init_kvm_softmmu(struct kvm_vcpu *vcpu,
                             union kvm_cpu_role cpu_role)
{
        struct kvm_mmu *context = &vcpu->arch.root_mmu;

        kvm_init_shadow_mmu(vcpu, cpu_role);

        context->get_guest_pgd     = get_cr3;
        context->get_pdptr         = kvm_pdptr_read;
        context->inject_page_fault = kvm_inject_page_fault;
}

static void init_kvm_nested_mmu(struct kvm_vcpu *vcpu,
                                union kvm_cpu_role new_mode)
{
        struct kvm_mmu *g_context = &vcpu->arch.nested_mmu;

        if (new_mode.as_u64 == g_context->cpu_role.as_u64)
                return;

        g_context->cpu_role.as_u64   = new_mode.as_u64;
        g_context->get_guest_pgd     = get_cr3;
        g_context->get_pdptr         = kvm_pdptr_read;
        g_context->inject_page_fault = kvm_inject_page_fault;

        /*
         * L2 page tables are never shadowed, so there is no need to sync
         * SPTEs.
         */
        g_context->invlpg            = NULL;

        /*
         * Note that arch.mmu->gva_to_gpa translates l2_gpa to l1_gpa using
         * L1's nested page tables (e.g. EPT12). The nested translation
         * of l2_gva to l1_gpa is done by arch.nested_mmu.gva_to_gpa using
         * L2's page tables as the first level of translation and L1's
         * nested page tables as the second level of translation. Basically
         * the gva_to_gpa functions between mmu and nested_mmu are swapped.
         */
        if (!is_paging(vcpu))
                g_context->gva_to_gpa = nonpaging_gva_to_gpa;
        else if (is_long_mode(vcpu))
                g_context->gva_to_gpa = paging64_gva_to_gpa;
        else if (is_pae(vcpu))
                g_context->gva_to_gpa = paging64_gva_to_gpa;
        else
                g_context->gva_to_gpa = paging32_gva_to_gpa;

        reset_guest_paging_metadata(vcpu, g_context);
}

void kvm_init_mmu(struct kvm_vcpu *vcpu)
{
        struct kvm_mmu_role_regs regs = vcpu_to_role_regs(vcpu);
        union kvm_cpu_role cpu_role = kvm_calc_cpu_role(vcpu, &regs);

        if (mmu_is_nested(vcpu))
                init_kvm_nested_mmu(vcpu, cpu_role);
        else if (tdp_enabled)
                init_kvm_tdp_mmu(vcpu, cpu_role);
        else
                init_kvm_softmmu(vcpu, cpu_role);
}
EXPORT_SYMBOL_GPL(kvm_init_mmu);

void kvm_mmu_after_set_cpuid(struct kvm_vcpu *vcpu)
{
        /*
         * Invalidate all MMU roles to force them to reinitialize as CPUID
         * information is factored into reserved bit calculations.
         *
         * Correctly handling multiple vCPU models with respect to paging and
         * physical address properties) in a single VM would require tracking
         * all relevant CPUID information in kvm_mmu_page_role. That is very
         * undesirable as it would increase the memory requirements for
         * gfn_track (see struct kvm_mmu_page_role comments).  For now that
         * problem is swept under the rug; KVM's CPUID API is horrific and
         * it's all but impossible to solve it without introducing a new API.
         */
        vcpu->arch.root_mmu.root_role.word = 0;
        vcpu->arch.guest_mmu.root_role.word = 0;
        vcpu->arch.nested_mmu.root_role.word = 0;
        vcpu->arch.root_mmu.cpu_role.ext.valid = 0;
        vcpu->arch.guest_mmu.cpu_role.ext.valid = 0;
        vcpu->arch.nested_mmu.cpu_role.ext.valid = 0;
        kvm_mmu_reset_context(vcpu);

        /*
         * Changing guest CPUID after KVM_RUN is forbidden, see the comment in
         * kvm_arch_vcpu_ioctl().
         */
        KVM_BUG_ON(vcpu->arch.last_vmentry_cpu != -1, vcpu->kvm);
}

void kvm_mmu_reset_context(struct kvm_vcpu *vcpu)
{
        kvm_mmu_unload(vcpu);
        kvm_init_mmu(vcpu);
}
EXPORT_SYMBOL_GPL(kvm_mmu_reset_context);

int kvm_mmu_load(struct kvm_vcpu *vcpu)
{
        int r;

        r = mmu_topup_memory_caches(vcpu, !vcpu->arch.mmu->root_role.direct);
        if (r)
                goto out;
        r = mmu_alloc_special_roots(vcpu);
        if (r)
                goto out;
        if (vcpu->arch.mmu->root_role.direct)
                r = mmu_alloc_direct_roots(vcpu);
        else
                r = mmu_alloc_shadow_roots(vcpu);
        if (r)
                goto out;

        kvm_mmu_sync_roots(vcpu);

        kvm_mmu_load_pgd(vcpu);

        /*
         * Flush any TLB entries for the new root, the provenance of the root
         * is unknown.  Even if KVM ensures there are no stale TLB entries
         * for a freed root, in theory another hypervisor could have left
         * stale entries.  Flushing on alloc also allows KVM to skip the TLB
         * flush when freeing a root (see kvm_tdp_mmu_put_root()).
         */
        static_call(kvm_x86_flush_tlb_current)(vcpu);
out:
        return r;
}

void kvm_mmu_unload(struct kvm_vcpu *vcpu)
{
        struct kvm *kvm = vcpu->kvm;

        kvm_mmu_free_roots(kvm, &vcpu->arch.root_mmu, KVM_MMU_ROOTS_ALL);
        WARN_ON(VALID_PAGE(vcpu->arch.root_mmu.root.hpa));
        kvm_mmu_free_roots(kvm, &vcpu->arch.guest_mmu, KVM_MMU_ROOTS_ALL);
        WARN_ON(VALID_PAGE(vcpu->arch.guest_mmu.root.hpa));
        vcpu_clear_mmio_info(vcpu, MMIO_GVA_ANY);
}

static bool is_obsolete_root(struct kvm *kvm, hpa_t root_hpa)
{
        struct kvm_mmu_page *sp;

        if (!VALID_PAGE(root_hpa))
                return false;

        /*
         * When freeing obsolete roots, treat roots as obsolete if they don't
         * have an associated shadow page.  This does mean KVM will get false
         * positives and free roots that don't strictly need to be freed, but
         * such false positives are relatively rare:
         *
         *  (a) only PAE paging and nested NPT has roots without shadow pages
         *  (b) remote reloads due to a memslot update obsoletes _all_ roots
         *  (c) KVM doesn't track previous roots for PAE paging, and the guest
         *      is unlikely to zap an in-use PGD.
         */
        sp = to_shadow_page(root_hpa);
        return !sp || is_obsolete_sp(kvm, sp);
}

static void __kvm_mmu_free_obsolete_roots(struct kvm *kvm, struct kvm_mmu *mmu)
{
        unsigned long roots_to_free = 0;
        int i;

        if (is_obsolete_root(kvm, mmu->root.hpa))
                roots_to_free |= KVM_MMU_ROOT_CURRENT;

        for (i = 0; i < KVM_MMU_NUM_PREV_ROOTS; i++) {
                if (is_obsolete_root(kvm, mmu->prev_roots[i].hpa))
                        roots_to_free |= KVM_MMU_ROOT_PREVIOUS(i);
        }

        if (roots_to_free)
                kvm_mmu_free_roots(kvm, mmu, roots_to_free);
}

void kvm_mmu_free_obsolete_roots(struct kvm_vcpu *vcpu)
{
        __kvm_mmu_free_obsolete_roots(vcpu->kvm, &vcpu->arch.root_mmu);
        __kvm_mmu_free_obsolete_roots(vcpu->kvm, &vcpu->arch.guest_mmu);
}

static u64 mmu_pte_write_fetch_gpte(struct kvm_vcpu *vcpu, gpa_t *gpa,
                                    int *bytes)
{
        u64 gentry = 0;
        int r;

        /*
         * Assume that the pte write on a page table of the same type
         * as the current vcpu paging mode since we update the sptes only
         * when they have the same mode.
         */
        if (is_pae(vcpu) && *bytes == 4) {
                /* Handle a 32-bit guest writing two halves of a 64-bit gpte */
                *gpa &= ~(gpa_t)7;
                *bytes = 8;
        }

        if (*bytes == 4 || *bytes == 8) {
                r = kvm_vcpu_read_guest_atomic(vcpu, *gpa, &gentry, *bytes);
                if (r)
                        gentry = 0;
        }

        return gentry;
}

/*
 * If we're seeing too many writes to a page, it may no longer be a page table,
 * or we may be forking, in which case it is better to unmap the page.
 */
static bool detect_write_flooding(struct kvm_mmu_page *sp)
{
        /*
         * Skip write-flooding detected for the sp whose level is 1, because
         * it can become unsync, then the guest page is not write-protected.
         */
        if (sp->role.level == PG_LEVEL_4K)
                return false;

        atomic_inc(&sp->write_flooding_count);
        return atomic_read(&sp->write_flooding_count) >= 3;
}

/*
 * Misaligned accesses are too much trouble to fix up; also, they usually
 * indicate a page is not used as a page table.
 */
static bool detect_write_misaligned(struct kvm_mmu_page *sp, gpa_t gpa,
                                    int bytes)
{
        unsigned offset, pte_size, misaligned;

        pgprintk("misaligned: gpa %llx bytes %d role %x\n",
                 gpa, bytes, sp->role.word);

        offset = offset_in_page(gpa);
        pte_size = sp->role.has_4_byte_gpte ? 4 : 8;

        /*
         * Sometimes, the OS only writes the last one bytes to update status
         * bits, for example, in linux, andb instruction is used in clear_bit().
         */
        if (!(offset & (pte_size - 1)) && bytes == 1)
                return false;

        misaligned = (offset ^ (offset + bytes - 1)) & ~(pte_size - 1);
        misaligned |= bytes < 4;

        return misaligned;
}

static u64 *get_written_sptes(struct kvm_mmu_page *sp, gpa_t gpa, int *nspte)
{
        unsigned page_offset, quadrant;
        u64 *spte;
        int level;

        page_offset = offset_in_page(gpa);
        level = sp->role.level;
        *nspte = 1;
        if (sp->role.has_4_byte_gpte) {
                page_offset <<= 1;      /* 32->64 */
                /*
                 * A 32-bit pde maps 4MB while the shadow pdes map
                 * only 2MB.  So we need to double the offset again
                 * and zap two pdes instead of one.
                 */
                if (level == PT32_ROOT_LEVEL) {
                        page_offset &= ~7; /* kill rounding error */
                        page_offset <<= 1;
                        *nspte = 2;
                }
                quadrant = page_offset >> PAGE_SHIFT;
                page_offset &= ~PAGE_MASK;
                if (quadrant != sp->role.quadrant)
                        return NULL;
        }

        spte = &sp->spt[page_offset / sizeof(*spte)];
        return spte;
}

static void kvm_mmu_pte_write(struct kvm_vcpu *vcpu, gpa_t gpa,
                              const u8 *new, int bytes,
                              struct kvm_page_track_notifier_node *node)
{
        gfn_t gfn = gpa >> PAGE_SHIFT;
        struct kvm_mmu_page *sp;
        LIST_HEAD(invalid_list);
        u64 entry, gentry, *spte;
        int npte;
        bool flush = false;

        /*
         * If we don't have indirect shadow pages, it means no page is
         * write-protected, so we can exit simply.
         */
        if (!READ_ONCE(vcpu->kvm->arch.indirect_shadow_pages))
                return;

        pgprintk("%s: gpa %llx bytes %d\n", __func__, gpa, bytes);

        write_lock(&vcpu->kvm->mmu_lock);

        gentry = mmu_pte_write_fetch_gpte(vcpu, &gpa, &bytes);

        ++vcpu->kvm->stat.mmu_pte_write;

        for_each_gfn_valid_sp_with_gptes(vcpu->kvm, sp, gfn) {
                if (detect_write_misaligned(sp, gpa, bytes) ||
                      detect_write_flooding(sp)) {
                        kvm_mmu_prepare_zap_page(vcpu->kvm, sp, &invalid_list);
                        ++vcpu->kvm->stat.mmu_flooded;
                        continue;
                }

                spte = get_written_sptes(sp, gpa, &npte);
                if (!spte)
                        continue;

                while (npte--) {
                        entry = *spte;
                        mmu_page_zap_pte(vcpu->kvm, sp, spte, NULL);
                        if (gentry && sp->role.level != PG_LEVEL_4K)
                                ++vcpu->kvm->stat.mmu_pde_zapped;
                        if (is_shadow_present_pte(entry))
                                flush = true;
                        ++spte;
                }
        }
        kvm_mmu_remote_flush_or_zap(vcpu->kvm, &invalid_list, flush);
        write_unlock(&vcpu->kvm->mmu_lock);
}

int noinline kvm_mmu_page_fault(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa, u64 error_code,
                       void *insn, int insn_len)
{
        int r, emulation_type = EMULTYPE_PF;
        bool direct = vcpu->arch.mmu->root_role.direct;

        if (WARN_ON(!VALID_PAGE(vcpu->arch.mmu->root.hpa)))
                return RET_PF_RETRY;

        r = RET_PF_INVALID;
        if (unlikely(error_code & PFERR_RSVD_MASK)) {
                r = handle_mmio_page_fault(vcpu, cr2_or_gpa, direct);
                if (r == RET_PF_EMULATE)
                        goto emulate;
        }

        if (r == RET_PF_INVALID) {
                r = kvm_mmu_do_page_fault(vcpu, cr2_or_gpa,
                                          lower_32_bits(error_code), false);
                if (KVM_BUG_ON(r == RET_PF_INVALID, vcpu->kvm))
                        return -EIO;
        }

        if (r < 0)
                return r;
        if (r != RET_PF_EMULATE)
                return 1;

        /*
         * Before emulating the instruction, check if the error code
         * was due to a RO violation while translating the guest page.
         * This can occur when using nested virtualization with nested
         * paging in both guests. If true, we simply unprotect the page
         * and resume the guest.
         */
        if (vcpu->arch.mmu->root_role.direct &&
            (error_code & PFERR_NESTED_GUEST_PAGE) == PFERR_NESTED_GUEST_PAGE) {
                kvm_mmu_unprotect_page(vcpu->kvm, gpa_to_gfn(cr2_or_gpa));
                return 1;
        }

        /*
         * vcpu->arch.mmu.page_fault returned RET_PF_EMULATE, but we can still
         * optimistically try to just unprotect the page and let the processor
         * re-execute the instruction that caused the page fault.  Do not allow
         * retrying MMIO emulation, as it's not only pointless but could also
         * cause us to enter an infinite loop because the processor will keep
         * faulting on the non-existent MMIO address.  Retrying an instruction
         * from a nested guest is also pointless and dangerous as we are only
         * explicitly shadowing L1's page tables, i.e. unprotecting something
         * for L1 isn't going to magically fix whatever issue cause L2 to fail.
         */
        if (!mmio_info_in_cache(vcpu, cr2_or_gpa, direct) && !is_guest_mode(vcpu))
                emulation_type |= EMULTYPE_ALLOW_RETRY_PF;
emulate:
        return x86_emulate_instruction(vcpu, cr2_or_gpa, emulation_type, insn,
                                       insn_len);
}
EXPORT_SYMBOL_GPL(kvm_mmu_page_fault);

void kvm_mmu_invalidate_gva(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu,
                            gva_t gva, hpa_t root_hpa)
{
        int i;

        /* It's actually a GPA for vcpu->arch.guest_mmu.  */
        if (mmu != &vcpu->arch.guest_mmu) {
                /* INVLPG on a non-canonical address is a NOP according to the SDM.  */
                if (is_noncanonical_address(gva, vcpu))
                        return;

                static_call(kvm_x86_flush_tlb_gva)(vcpu, gva);
        }

        if (!mmu->invlpg)
                return;

        if (root_hpa == INVALID_PAGE) {
                mmu->invlpg(vcpu, gva, mmu->root.hpa);

                /*
                 * INVLPG is required to invalidate any global mappings for the VA,
                 * irrespective of PCID. Since it would take us roughly similar amount
                 * of work to determine whether any of the prev_root mappings of the VA
                 * is marked global, or to just sync it blindly, so we might as well
                 * just always sync it.
                 *
                 * Mappings not reachable via the current cr3 or the prev_roots will be
                 * synced when switching to that cr3, so nothing needs to be done here
                 * for them.
                 */
                for (i = 0; i < KVM_MMU_NUM_PREV_ROOTS; i++)
                        if (VALID_PAGE(mmu->prev_roots[i].hpa))
                                mmu->invlpg(vcpu, gva, mmu->prev_roots[i].hpa);
        } else {
                mmu->invlpg(vcpu, gva, root_hpa);
        }
}

void kvm_mmu_invlpg(struct kvm_vcpu *vcpu, gva_t gva)
{
        kvm_mmu_invalidate_gva(vcpu, vcpu->arch.walk_mmu, gva, INVALID_PAGE);
        ++vcpu->stat.invlpg;
}
EXPORT_SYMBOL_GPL(kvm_mmu_invlpg);


void kvm_mmu_invpcid_gva(struct kvm_vcpu *vcpu, gva_t gva, unsigned long pcid)
{
        struct kvm_mmu *mmu = vcpu->arch.mmu;
        bool tlb_flush = false;
        uint i;

        if (pcid == kvm_get_active_pcid(vcpu)) {
                if (mmu->invlpg)
                        mmu->invlpg(vcpu, gva, mmu->root.hpa);
                tlb_flush = true;
        }

        for (i = 0; i < KVM_MMU_NUM_PREV_ROOTS; i++) {
                if (VALID_PAGE(mmu->prev_roots[i].hpa) &&
                    pcid == kvm_get_pcid(vcpu, mmu->prev_roots[i].pgd)) {
                        if (mmu->invlpg)
                                mmu->invlpg(vcpu, gva, mmu->prev_roots[i].hpa);
                        tlb_flush = true;
                }
        }

        if (tlb_flush)
                static_call(kvm_x86_flush_tlb_gva)(vcpu, gva);

        ++vcpu->stat.invlpg;

        /*
         * Mappings not reachable via the current cr3 or the prev_roots will be
         * synced when switching to that cr3, so nothing needs to be done here
         * for them.
         */
}

void kvm_configure_mmu(bool enable_tdp, int tdp_forced_root_level,
                       int tdp_max_root_level, int tdp_huge_page_level)
{
        tdp_enabled = enable_tdp;
        tdp_root_level = tdp_forced_root_level;
        max_tdp_level = tdp_max_root_level;

#ifdef CONFIG_X86_64
        tdp_mmu_enabled = tdp_mmu_allowed && tdp_enabled;
#endif
        /*
         * max_huge_page_level reflects KVM's MMU capabilities irrespective
         * of kernel support, e.g. KVM may be capable of using 1GB pages when
         * the kernel is not.  But, KVM never creates a page size greater than
         * what is used by the kernel for any given HVA, i.e. the kernel's
         * capabilities are ultimately consulted by kvm_mmu_hugepage_adjust().
         */
        if (tdp_enabled)
                max_huge_page_level = tdp_huge_page_level;
        else if (boot_cpu_has(X86_FEATURE_GBPAGES))
                max_huge_page_level = PG_LEVEL_1G;
        else
                max_huge_page_level = PG_LEVEL_2M;
}
EXPORT_SYMBOL_GPL(kvm_configure_mmu);

/* The return value indicates if tlb flush on all vcpus is needed. */
typedef bool (*slot_level_handler) (struct kvm *kvm,
                                    struct kvm_rmap_head *rmap_head,
                                    const struct kvm_memory_slot *slot);

/* The caller should hold mmu-lock before calling this function. */
static __always_inline bool
slot_handle_level_range(struct kvm *kvm, const struct kvm_memory_slot *memslot,
                        slot_level_handler fn, int start_level, int end_level,
                        gfn_t start_gfn, gfn_t end_gfn, bool flush_on_yield,
                        bool flush)
{
        struct slot_rmap_walk_iterator iterator;

        for_each_slot_rmap_range(memslot, start_level, end_level, start_gfn,
                        end_gfn, &iterator) {
                if (iterator.rmap)
                        flush |= fn(kvm, iterator.rmap, memslot);

                if (need_resched() || rwlock_needbreak(&kvm->mmu_lock)) {
                        if (flush && flush_on_yield) {
                                kvm_flush_remote_tlbs_with_address(kvm,
                                                start_gfn,
                                                iterator.gfn - start_gfn + 1);
                                flush = false;
                        }
                        cond_resched_rwlock_write(&kvm->mmu_lock);
                }
        }

        return flush;
}

static __always_inline bool
slot_handle_level(struct kvm *kvm, const struct kvm_memory_slot *memslot,
                  slot_level_handler fn, int start_level, int end_level,
                  bool flush_on_yield)
{
        return slot_handle_level_range(kvm, memslot, fn, start_level,
                        end_level, memslot->base_gfn,
                        memslot->base_gfn + memslot->npages - 1,
                        flush_on_yield, false);
}

static __always_inline bool
slot_handle_level_4k(struct kvm *kvm, const struct kvm_memory_slot *memslot,
                     slot_level_handler fn, bool flush_on_yield)
{
        return slot_handle_level(kvm, memslot, fn, PG_LEVEL_4K,
                                 PG_LEVEL_4K, flush_on_yield);
}

static void free_mmu_pages(struct kvm_mmu *mmu)
{
        if (!tdp_enabled && mmu->pae_root)
                set_memory_encrypted((unsigned long)mmu->pae_root, 1);
        free_page((unsigned long)mmu->pae_root);
        free_page((unsigned long)mmu->pml4_root);
        free_page((unsigned long)mmu->pml5_root);
}

static int __kvm_mmu_create(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu)
{
        struct page *page;
        int i;

        mmu->root.hpa = INVALID_PAGE;
        mmu->root.pgd = 0;
        for (i = 0; i < KVM_MMU_NUM_PREV_ROOTS; i++)
                mmu->prev_roots[i] = KVM_MMU_ROOT_INFO_INVALID;

        /* vcpu->arch.guest_mmu isn't used when !tdp_enabled. */
        if (!tdp_enabled && mmu == &vcpu->arch.guest_mmu)
                return 0;

        /*
         * When using PAE paging, the four PDPTEs are treated as 'root' pages,
         * while the PDP table is a per-vCPU construct that's allocated at MMU
         * creation.  When emulating 32-bit mode, cr3 is only 32 bits even on
         * x86_64.  Therefore we need to allocate the PDP table in the first
         * 4GB of memory, which happens to fit the DMA32 zone.  TDP paging
         * generally doesn't use PAE paging and can skip allocating the PDP
         * table.  The main exception, handled here, is SVM's 32-bit NPT.  The
         * other exception is for shadowing L1's 32-bit or PAE NPT on 64-bit
         * KVM; that horror is handled on-demand by mmu_alloc_special_roots().
         */
        if (tdp_enabled && kvm_mmu_get_tdp_level(vcpu) > PT32E_ROOT_LEVEL)
                return 0;

        page = alloc_page(GFP_KERNEL_ACCOUNT | __GFP_DMA32);
        if (!page)
                return -ENOMEM;

        mmu->pae_root = page_address(page);

        /*
         * CR3 is only 32 bits when PAE paging is used, thus it's impossible to
         * get the CPU to treat the PDPTEs as encrypted.  Decrypt the page so
         * that KVM's writes and the CPU's reads get along.  Note, this is
         * only necessary when using shadow paging, as 64-bit NPT can get at
         * the C-bit even when shadowing 32-bit NPT, and SME isn't supported
         * by 32-bit kernels (when KVM itself uses 32-bit NPT).
         */
        if (!tdp_enabled)
                set_memory_decrypted((unsigned long)mmu->pae_root, 1);
        else
                WARN_ON_ONCE(shadow_me_value);

        for (i = 0; i < 4; ++i)
                mmu->pae_root[i] = INVALID_PAE_ROOT;

        return 0;
}

int kvm_mmu_create(struct kvm_vcpu *vcpu)
{
        int ret;

        vcpu->arch.mmu_pte_list_desc_cache.kmem_cache = pte_list_desc_cache;
        vcpu->arch.mmu_pte_list_desc_cache.gfp_zero = __GFP_ZERO;

        vcpu->arch.mmu_page_header_cache.kmem_cache = mmu_page_header_cache;
        vcpu->arch.mmu_page_header_cache.gfp_zero = __GFP_ZERO;

        vcpu->arch.mmu_shadow_page_cache.gfp_zero = __GFP_ZERO;

        vcpu->arch.mmu = &vcpu->arch.root_mmu;
        vcpu->arch.walk_mmu = &vcpu->arch.root_mmu;

        ret = __kvm_mmu_create(vcpu, &vcpu->arch.guest_mmu);
        if (ret)
                return ret;

        ret = __kvm_mmu_create(vcpu, &vcpu->arch.root_mmu);
        if (ret)
                goto fail_allocate_root;

        return ret;
 fail_allocate_root:
        free_mmu_pages(&vcpu->arch.guest_mmu);
        return ret;
}

#define BATCH_ZAP_PAGES 10
static void kvm_zap_obsolete_pages(struct kvm *kvm)
{
        struct kvm_mmu_page *sp, *node;
        int nr_zapped, batch = 0;
        bool unstable;

restart:
        list_for_each_entry_safe_reverse(sp, node,
              &kvm->arch.active_mmu_pages, link) {
                /*
                 * No obsolete valid page exists before a newly created page
                 * since active_mmu_pages is a FIFO list.
                 */
                if (!is_obsolete_sp(kvm, sp))
                        break;

                /*
                 * Invalid pages should never land back on the list of active
                 * pages.  Skip the bogus page, otherwise we'll get stuck in an
                 * infinite loop if the page gets put back on the list (again).
                 */
                if (WARN_ON(sp->role.invalid))
                        continue;

                /*
                 * No need to flush the TLB since we're only zapping shadow
                 * pages with an obsolete generation number and all vCPUS have
                 * loaded a new root, i.e. the shadow pages being zapped cannot
                 * be in active use by the guest.
                 */
                if (batch >= BATCH_ZAP_PAGES &&
                    cond_resched_rwlock_write(&kvm->mmu_lock)) {
                        batch = 0;
                        goto restart;
                }

                unstable = __kvm_mmu_prepare_zap_page(kvm, sp,
                                &kvm->arch.zapped_obsolete_pages, &nr_zapped);
                batch += nr_zapped;

                if (unstable)
                        goto restart;
        }

        /*
         * Kick all vCPUs (via remote TLB flush) before freeing the page tables
         * to ensure KVM is not in the middle of a lockless shadow page table
         * walk, which may reference the pages.  The remote TLB flush itself is
         * not required and is simply a convenient way to kick vCPUs as needed.
         * KVM performs a local TLB flush when allocating a new root (see
         * kvm_mmu_load()), and the reload in the caller ensure no vCPUs are
         * running with an obsolete MMU.
         */
        kvm_mmu_commit_zap_page(kvm, &kvm->arch.zapped_obsolete_pages);
}

/*
 * Fast invalidate all shadow pages and use lock-break technique
 * to zap obsolete pages.
 *
 * It's required when memslot is being deleted or VM is being
 * destroyed, in these cases, we should ensure that KVM MMU does
 * not use any resource of the being-deleted slot or all slots
 * after calling the function.
 */
static void kvm_mmu_zap_all_fast(struct kvm *kvm)
{
        lockdep_assert_held(&kvm->slots_lock);

        write_lock(&kvm->mmu_lock);
        trace_kvm_mmu_zap_all_fast(kvm);

        /*
         * Toggle mmu_valid_gen between '0' and '1'.  Because slots_lock is
         * held for the entire duration of zapping obsolete pages, it's
         * impossible for there to be multiple invalid generations associated
         * with *valid* shadow pages at any given time, i.e. there is exactly
         * one valid generation and (at most) one invalid generation.
         */
        kvm->arch.mmu_valid_gen = kvm->arch.mmu_valid_gen ? 0 : 1;

        /*
         * In order to ensure all vCPUs drop their soon-to-be invalid roots,
         * invalidating TDP MMU roots must be done while holding mmu_lock for
         * write and in the same critical section as making the reload request,
         * e.g. before kvm_zap_obsolete_pages() could drop mmu_lock and yield.
         */
        if (tdp_mmu_enabled)
                kvm_tdp_mmu_invalidate_all_roots(kvm);

        /*
         * Notify all vcpus to reload its shadow page table and flush TLB.
         * Then all vcpus will switch to new shadow page table with the new
         * mmu_valid_gen.
         *
         * Note: we need to do this under the protection of mmu_lock,
         * otherwise, vcpu would purge shadow page but miss tlb flush.
         */
        kvm_make_all_cpus_request(kvm, KVM_REQ_MMU_FREE_OBSOLETE_ROOTS);

        kvm_zap_obsolete_pages(kvm);

        write_unlock(&kvm->mmu_lock);

        /*
         * Zap the invalidated TDP MMU roots, all SPTEs must be dropped before
         * returning to the caller, e.g. if the zap is in response to a memslot
         * deletion, mmu_notifier callbacks will be unable to reach the SPTEs
         * associated with the deleted memslot once the update completes, and
         * Deferring the zap until the final reference to the root is put would
         * lead to use-after-free.
         */
        if (tdp_mmu_enabled)
                kvm_tdp_mmu_zap_invalidated_roots(kvm);
}

static bool kvm_has_zapped_obsolete_pages(struct kvm *kvm)
{
        return unlikely(!list_empty_careful(&kvm->arch.zapped_obsolete_pages));
}

static void kvm_mmu_invalidate_zap_pages_in_memslot(struct kvm *kvm,
                        struct kvm_memory_slot *slot,
                        struct kvm_page_track_notifier_node *node)
{
        kvm_mmu_zap_all_fast(kvm);
}

int kvm_mmu_init_vm(struct kvm *kvm)
{
        struct kvm_page_track_notifier_node *node = &kvm->arch.mmu_sp_tracker;
        int r;

        INIT_LIST_HEAD(&kvm->arch.active_mmu_pages);
        INIT_LIST_HEAD(&kvm->arch.zapped_obsolete_pages);
        INIT_LIST_HEAD(&kvm->arch.possible_nx_huge_pages);
        spin_lock_init(&kvm->arch.mmu_unsync_pages_lock);

        if (tdp_mmu_enabled) {
                r = kvm_mmu_init_tdp_mmu(kvm);
                if (r < 0)
                        return r;
        }

        node->track_write = kvm_mmu_pte_write;
        node->track_flush_slot = kvm_mmu_invalidate_zap_pages_in_memslot;
        kvm_page_track_register_notifier(kvm, node);

        kvm->arch.split_page_header_cache.kmem_cache = mmu_page_header_cache;
        kvm->arch.split_page_header_cache.gfp_zero = __GFP_ZERO;

        kvm->arch.split_shadow_page_cache.gfp_zero = __GFP_ZERO;

        kvm->arch.split_desc_cache.kmem_cache = pte_list_desc_cache;
        kvm->arch.split_desc_cache.gfp_zero = __GFP_ZERO;

        return 0;
}

static void mmu_free_vm_memory_caches(struct kvm *kvm)
{
        kvm_mmu_free_memory_cache(&kvm->arch.split_desc_cache);
        kvm_mmu_free_memory_cache(&kvm->arch.split_page_header_cache);
        kvm_mmu_free_memory_cache(&kvm->arch.split_shadow_page_cache);
}

void kvm_mmu_uninit_vm(struct kvm *kvm)
{
        struct kvm_page_track_notifier_node *node = &kvm->arch.mmu_sp_tracker;

        kvm_page_track_unregister_notifier(kvm, node);

        if (tdp_mmu_enabled)
                kvm_mmu_uninit_tdp_mmu(kvm);

        mmu_free_vm_memory_caches(kvm);
}

static bool kvm_rmap_zap_gfn_range(struct kvm *kvm, gfn_t gfn_start, gfn_t gfn_end)
{
        const struct kvm_memory_slot *memslot;
        struct kvm_memslots *slots;
        struct kvm_memslot_iter iter;
        bool flush = false;
        gfn_t start, end;
        int i;

        if (!kvm_memslots_have_rmaps(kvm))
                return flush;

        for (i = 0; i < KVM_ADDRESS_SPACE_NUM; i++) {
                slots = __kvm_memslots(kvm, i);

                kvm_for_each_memslot_in_gfn_range(&iter, slots, gfn_start, gfn_end) {
                        memslot = iter.slot;
                        start = max(gfn_start, memslot->base_gfn);
                        end = min(gfn_end, memslot->base_gfn + memslot->npages);
                        if (WARN_ON_ONCE(start >= end))
                                continue;

                        flush = slot_handle_level_range(kvm, memslot, __kvm_zap_rmap,
                                                        PG_LEVEL_4K, KVM_MAX_HUGEPAGE_LEVEL,
                                                        start, end - 1, true, flush);
                }
        }

        return flush;
}

/*
 * Invalidate (zap) SPTEs that cover GFNs from gfn_start and up to gfn_end
 * (not including it)
 */
void kvm_zap_gfn_range(struct kvm *kvm, gfn_t gfn_start, gfn_t gfn_end)
{
        bool flush;
        int i;

        if (WARN_ON_ONCE(gfn_end <= gfn_start))
                return;

        write_lock(&kvm->mmu_lock);

        kvm_mmu_invalidate_begin(kvm, 0, -1ul);

        flush = kvm_rmap_zap_gfn_range(kvm, gfn_start, gfn_end);

        if (tdp_mmu_enabled) {
                for (i = 0; i < KVM_ADDRESS_SPACE_NUM; i++)
                        flush = kvm_tdp_mmu_zap_leafs(kvm, i, gfn_start,
                                                      gfn_end, true, flush);
        }

        if (flush)
                kvm_flush_remote_tlbs_with_address(kvm, gfn_start,
                                                   gfn_end - gfn_start);

        kvm_mmu_invalidate_end(kvm, 0, -1ul);

        write_unlock(&kvm->mmu_lock);
}

static bool slot_rmap_write_protect(struct kvm *kvm,
                                    struct kvm_rmap_head *rmap_head,
                                    const struct kvm_memory_slot *slot)
{
        return rmap_write_protect(rmap_head, false);
}

void kvm_mmu_slot_remove_write_access(struct kvm *kvm,
                                      const struct kvm_memory_slot *memslot,
                                      int start_level)
{
        if (kvm_memslots_have_rmaps(kvm)) {
                write_lock(&kvm->mmu_lock);
                slot_handle_level(kvm, memslot, slot_rmap_write_protect,
                                  start_level, KVM_MAX_HUGEPAGE_LEVEL, false);
                write_unlock(&kvm->mmu_lock);
        }

        if (tdp_mmu_enabled) {
                read_lock(&kvm->mmu_lock);
                kvm_tdp_mmu_wrprot_slot(kvm, memslot, start_level);
                read_unlock(&kvm->mmu_lock);
        }
}

static inline bool need_topup(struct kvm_mmu_memory_cache *cache, int min)
{
        return kvm_mmu_memory_cache_nr_free_objects(cache) < min;
}

static bool need_topup_split_caches_or_resched(struct kvm *kvm)
{
        if (need_resched() || rwlock_needbreak(&kvm->mmu_lock))
                return true;

        /*
         * In the worst case, SPLIT_DESC_CACHE_MIN_NR_OBJECTS descriptors are needed
         * to split a single huge page. Calculating how many are actually needed
         * is possible but not worth the complexity.
         */
        return need_topup(&kvm->arch.split_desc_cache, SPLIT_DESC_CACHE_MIN_NR_OBJECTS) ||
               need_topup(&kvm->arch.split_page_header_cache, 1) ||
               need_topup(&kvm->arch.split_shadow_page_cache, 1);
}

static int topup_split_caches(struct kvm *kvm)
{
        /*
         * Allocating rmap list entries when splitting huge pages for nested
         * MMUs is uncommon as KVM needs to use a list if and only if there is
         * more than one rmap entry for a gfn, i.e. requires an L1 gfn to be
         * aliased by multiple L2 gfns and/or from multiple nested roots with
         * different roles.  Aliasing gfns when using TDP is atypical for VMMs;
         * a few gfns are often aliased during boot, e.g. when remapping BIOS,
         * but aliasing rarely occurs post-boot or for many gfns.  If there is
         * only one rmap entry, rmap->val points directly at that one entry and
         * doesn't need to allocate a list.  Buffer the cache by the default
         * capacity so that KVM doesn't have to drop mmu_lock to topup if KVM
         * encounters an aliased gfn or two.
         */
        const int capacity = SPLIT_DESC_CACHE_MIN_NR_OBJECTS +
                             KVM_ARCH_NR_OBJS_PER_MEMORY_CACHE;
        int r;

        lockdep_assert_held(&kvm->slots_lock);

        r = __kvm_mmu_topup_memory_cache(&kvm->arch.split_desc_cache, capacity,
                                         SPLIT_DESC_CACHE_MIN_NR_OBJECTS);
        if (r)
                return r;

        r = kvm_mmu_topup_memory_cache(&kvm->arch.split_page_header_cache, 1);
        if (r)
                return r;

        return kvm_mmu_topup_memory_cache(&kvm->arch.split_shadow_page_cache, 1);
}

static struct kvm_mmu_page *shadow_mmu_get_sp_for_split(struct kvm *kvm, u64 *huge_sptep)
{
        struct kvm_mmu_page *huge_sp = sptep_to_sp(huge_sptep);
        struct shadow_page_caches caches = {};
        union kvm_mmu_page_role role;
        unsigned int access;
        gfn_t gfn;

        gfn = kvm_mmu_page_get_gfn(huge_sp, spte_index(huge_sptep));
        access = kvm_mmu_page_get_access(huge_sp, spte_index(huge_sptep));

        /*
         * Note, huge page splitting always uses direct shadow pages, regardless
         * of whether the huge page itself is mapped by a direct or indirect
         * shadow page, since the huge page region itself is being directly
         * mapped with smaller pages.
         */
        role = kvm_mmu_child_role(huge_sptep, /*direct=*/true, access);

        /* Direct SPs do not require a shadowed_info_cache. */
        caches.page_header_cache = &kvm->arch.split_page_header_cache;
        caches.shadow_page_cache = &kvm->arch.split_shadow_page_cache;

        /* Safe to pass NULL for vCPU since requesting a direct SP. */
        return __kvm_mmu_get_shadow_page(kvm, NULL, &caches, gfn, role);
}

static void shadow_mmu_split_huge_page(struct kvm *kvm,
                                       const struct kvm_memory_slot *slot,
                                       u64 *huge_sptep)

{
        struct kvm_mmu_memory_cache *cache = &kvm->arch.split_desc_cache;
        u64 huge_spte = READ_ONCE(*huge_sptep);
        struct kvm_mmu_page *sp;
        bool flush = false;
        u64 *sptep, spte;
        gfn_t gfn;
        int index;

        sp = shadow_mmu_get_sp_for_split(kvm, huge_sptep);

        for (index = 0; index < SPTE_ENT_PER_PAGE; index++) {
                sptep = &sp->spt[index];
                gfn = kvm_mmu_page_get_gfn(sp, index);

                /*
                 * The SP may already have populated SPTEs, e.g. if this huge
                 * page is aliased by multiple sptes with the same access
                 * permissions. These entries are guaranteed to map the same
                 * gfn-to-pfn translation since the SP is direct, so no need to
                 * modify them.
                 *
                 * However, if a given SPTE points to a lower level page table,
                 * that lower level page table may only be partially populated.
                 * Installing such SPTEs would effectively unmap a potion of the
                 * huge page. Unmapping guest memory always requires a TLB flush
                 * since a subsequent operation on the unmapped regions would
                 * fail to detect the need to flush.
                 */
                if (is_shadow_present_pte(*sptep)) {
                        flush |= !is_last_spte(*sptep, sp->role.level);
                        continue;
                }

                spte = make_huge_page_split_spte(kvm, huge_spte, sp->role, index);
                mmu_spte_set(sptep, spte);
                __rmap_add(kvm, cache, slot, sptep, gfn, sp->role.access);
        }

        __link_shadow_page(kvm, cache, huge_sptep, sp, flush);
}

static int shadow_mmu_try_split_huge_page(struct kvm *kvm,
                                          const struct kvm_memory_slot *slot,
                                          u64 *huge_sptep)
{
        struct kvm_mmu_page *huge_sp = sptep_to_sp(huge_sptep);
        int level, r = 0;
        gfn_t gfn;
        u64 spte;

        /* Grab information for the tracepoint before dropping the MMU lock. */
        gfn = kvm_mmu_page_get_gfn(huge_sp, spte_index(huge_sptep));
        level = huge_sp->role.level;
        spte = *huge_sptep;

        if (kvm_mmu_available_pages(kvm) <= KVM_MIN_FREE_MMU_PAGES) {
                r = -ENOSPC;
                goto out;
        }

        if (need_topup_split_caches_or_resched(kvm)) {
                write_unlock(&kvm->mmu_lock);
                cond_resched();
                /*
                 * If the topup succeeds, return -EAGAIN to indicate that the
                 * rmap iterator should be restarted because the MMU lock was
                 * dropped.
                 */
                r = topup_split_caches(kvm) ?: -EAGAIN;
                write_lock(&kvm->mmu_lock);
                goto out;
        }

        shadow_mmu_split_huge_page(kvm, slot, huge_sptep);

out:
        trace_kvm_mmu_split_huge_page(gfn, spte, level, r);
        return r;
}

static bool shadow_mmu_try_split_huge_pages(struct kvm *kvm,
                                            struct kvm_rmap_head *rmap_head,
                                            const struct kvm_memory_slot *slot)
{
        struct rmap_iterator iter;
        struct kvm_mmu_page *sp;
        u64 *huge_sptep;
        int r;

restart:
        for_each_rmap_spte(rmap_head, &iter, huge_sptep) {
                sp = sptep_to_sp(huge_sptep);

                /* TDP MMU is enabled, so rmap only contains nested MMU SPs. */
                if (WARN_ON_ONCE(!sp->role.guest_mode))
                        continue;

                /* The rmaps should never contain non-leaf SPTEs. */
                if (WARN_ON_ONCE(!is_large_pte(*huge_sptep)))
                        continue;

                /* SPs with level >PG_LEVEL_4K should never by unsync. */
                if (WARN_ON_ONCE(sp->unsync))
                        continue;

                /* Don't bother splitting huge pages on invalid SPs. */
                if (sp->role.invalid)
                        continue;

                r = shadow_mmu_try_split_huge_page(kvm, slot, huge_sptep);

                /*
                 * The split succeeded or needs to be retried because the MMU
                 * lock was dropped. Either way, restart the iterator to get it
                 * back into a consistent state.
                 */
                if (!r || r == -EAGAIN)
                        goto restart;

                /* The split failed and shouldn't be retried (e.g. -ENOMEM). */
                break;
        }

        return false;
}

static void kvm_shadow_mmu_try_split_huge_pages(struct kvm *kvm,
                                                const struct kvm_memory_slot *slot,
                                                gfn_t start, gfn_t end,
                                                int target_level)
{
        int level;

        /*
         * Split huge pages starting with KVM_MAX_HUGEPAGE_LEVEL and working
         * down to the target level. This ensures pages are recursively split
         * all the way to the target level. There's no need to split pages
         * already at the target level.
         */
        for (level = KVM_MAX_HUGEPAGE_LEVEL; level > target_level; level--) {
                slot_handle_level_range(kvm, slot, shadow_mmu_try_split_huge_pages,
                                        level, level, start, end - 1, true, false);
        }
}

/* Must be called with the mmu_lock held in write-mode. */
void kvm_mmu_try_split_huge_pages(struct kvm *kvm,
                                   const struct kvm_memory_slot *memslot,
                                   u64 start, u64 end,
                                   int target_level)
{
        if (!tdp_mmu_enabled)
                return;

        if (kvm_memslots_have_rmaps(kvm))
                kvm_shadow_mmu_try_split_huge_pages(kvm, memslot, start, end, target_level);

        kvm_tdp_mmu_try_split_huge_pages(kvm, memslot, start, end, target_level, false);

        /*
         * A TLB flush is unnecessary at this point for the same resons as in
         * kvm_mmu_slot_try_split_huge_pages().
         */
}

void kvm_mmu_slot_try_split_huge_pages(struct kvm *kvm,
                                        const struct kvm_memory_slot *memslot,
                                        int target_level)
{
        u64 start = memslot->base_gfn;
        u64 end = start + memslot->npages;

        if (!tdp_mmu_enabled)
                return;

        if (kvm_memslots_have_rmaps(kvm)) {
                write_lock(&kvm->mmu_lock);
                kvm_shadow_mmu_try_split_huge_pages(kvm, memslot, start, end, target_level);
                write_unlock(&kvm->mmu_lock);
        }

        read_lock(&kvm->mmu_lock);
        kvm_tdp_mmu_try_split_huge_pages(kvm, memslot, start, end, target_level, true);
        read_unlock(&kvm->mmu_lock);

        /*
         * No TLB flush is necessary here. KVM will flush TLBs after
         * write-protecting and/or clearing dirty on the newly split SPTEs to
         * ensure that guest writes are reflected in the dirty log before the
         * ioctl to enable dirty logging on this memslot completes. Since the
         * split SPTEs retain the write and dirty bits of the huge SPTE, it is
         * safe for KVM to decide if a TLB flush is necessary based on the split
         * SPTEs.
         */
}

static bool kvm_mmu_zap_collapsible_spte(struct kvm *kvm,
                                         struct kvm_rmap_head *rmap_head,
                                         const struct kvm_memory_slot *slot)
{
        u64 *sptep;
        struct rmap_iterator iter;
        int need_tlb_flush = 0;
        struct kvm_mmu_page *sp;

restart:
        for_each_rmap_spte(rmap_head, &iter, sptep) {
                sp = sptep_to_sp(sptep);

                /*
                 * We cannot do huge page mapping for indirect shadow pages,
                 * which are found on the last rmap (level = 1) when not using
                 * tdp; such shadow pages are synced with the page table in
                 * the guest, and the guest page table is using 4K page size
                 * mapping if the indirect sp has level = 1.
                 */
                if (sp->role.direct &&
                    sp->role.level < kvm_mmu_max_mapping_level(kvm, slot, sp->gfn,
                                                               PG_LEVEL_NUM)) {
                        kvm_zap_one_rmap_spte(kvm, rmap_head, sptep);

                        if (kvm_available_flush_tlb_with_range())
                                kvm_flush_remote_tlbs_with_address(kvm, sp->gfn,
                                        KVM_PAGES_PER_HPAGE(sp->role.level));
                        else
                                need_tlb_flush = 1;

                        goto restart;
                }
        }

        return need_tlb_flush;
}

static void kvm_rmap_zap_collapsible_sptes(struct kvm *kvm,
                                           const struct kvm_memory_slot *slot)
{
        /*
         * Note, use KVM_MAX_HUGEPAGE_LEVEL - 1 since there's no need to zap
         * pages that are already mapped at the maximum hugepage level.
         */
        if (slot_handle_level(kvm, slot, kvm_mmu_zap_collapsible_spte,
                              PG_LEVEL_4K, KVM_MAX_HUGEPAGE_LEVEL - 1, true))
                kvm_arch_flush_remote_tlbs_memslot(kvm, slot);
}

void kvm_mmu_zap_collapsible_sptes(struct kvm *kvm,
                                   const struct kvm_memory_slot *slot)
{
        if (kvm_memslots_have_rmaps(kvm)) {
                write_lock(&kvm->mmu_lock);
                kvm_rmap_zap_collapsible_sptes(kvm, slot);
                write_unlock(&kvm->mmu_lock);
        }

        if (tdp_mmu_enabled) {
                read_lock(&kvm->mmu_lock);
                kvm_tdp_mmu_zap_collapsible_sptes(kvm, slot);
                read_unlock(&kvm->mmu_lock);
        }
}

void kvm_arch_flush_remote_tlbs_memslot(struct kvm *kvm,
                                        const struct kvm_memory_slot *memslot)
{
        /*
         * All current use cases for flushing the TLBs for a specific memslot
         * related to dirty logging, and many do the TLB flush out of mmu_lock.
         * The interaction between the various operations on memslot must be
         * serialized by slots_locks to ensure the TLB flush from one operation
         * is observed by any other operation on the same memslot.
         */
        lockdep_assert_held(&kvm->slots_lock);
        kvm_flush_remote_tlbs_with_address(kvm, memslot->base_gfn,
                                           memslot->npages);
}

void kvm_mmu_slot_leaf_clear_dirty(struct kvm *kvm,
                                   const struct kvm_memory_slot *memslot)
{
        if (kvm_memslots_have_rmaps(kvm)) {
                write_lock(&kvm->mmu_lock);
                /*
                 * Clear dirty bits only on 4k SPTEs since the legacy MMU only
                 * support dirty logging at a 4k granularity.
                 */
                slot_handle_level_4k(kvm, memslot, __rmap_clear_dirty, false);
                write_unlock(&kvm->mmu_lock);
        }

        if (tdp_mmu_enabled) {
                read_lock(&kvm->mmu_lock);
                kvm_tdp_mmu_clear_dirty_slot(kvm, memslot);
                read_unlock(&kvm->mmu_lock);
        }

        /*
         * The caller will flush the TLBs after this function returns.
         *
         * It's also safe to flush TLBs out of mmu lock here as currently this
         * function is only used for dirty logging, in which case flushing TLB
         * out of mmu lock also guarantees no dirty pages will be lost in
         * dirty_bitmap.
         */
}

void kvm_mmu_zap_all(struct kvm *kvm)
{
        struct kvm_mmu_page *sp, *node;
        LIST_HEAD(invalid_list);
        int ign;

        write_lock(&kvm->mmu_lock);
restart:
        list_for_each_entry_safe(sp, node, &kvm->arch.active_mmu_pages, link) {
                if (WARN_ON(sp->role.invalid))
                        continue;
                if (__kvm_mmu_prepare_zap_page(kvm, sp, &invalid_list, &ign))
                        goto restart;
                if (cond_resched_rwlock_write(&kvm->mmu_lock))
                        goto restart;
        }

        kvm_mmu_commit_zap_page(kvm, &invalid_list);

        if (tdp_mmu_enabled)
                kvm_tdp_mmu_zap_all(kvm);

        write_unlock(&kvm->mmu_lock);
}

void kvm_mmu_invalidate_mmio_sptes(struct kvm *kvm, u64 gen)
{
        WARN_ON(gen & KVM_MEMSLOT_GEN_UPDATE_IN_PROGRESS);

        gen &= MMIO_SPTE_GEN_MASK;

        /*
         * Generation numbers are incremented in multiples of the number of
         * address spaces in order to provide unique generations across all
         * address spaces.  Strip what is effectively the address space
         * modifier prior to checking for a wrap of the MMIO generation so
         * that a wrap in any address space is detected.
         */
        gen &= ~((u64)KVM_ADDRESS_SPACE_NUM - 1);

        /*
         * The very rare case: if the MMIO generation number has wrapped,
         * zap all shadow pages.
         */
        if (unlikely(gen == 0)) {
                kvm_debug_ratelimited("kvm: zapping shadow pages for mmio generation wraparound\n");
                kvm_mmu_zap_all_fast(kvm);
        }
}

static unsigned long
mmu_shrink_scan(struct shrinker *shrink, struct shrink_control *sc)
{
        struct kvm *kvm;
        int nr_to_scan = sc->nr_to_scan;
        unsigned long freed = 0;

        mutex_lock(&kvm_lock);

        list_for_each_entry(kvm, &vm_list, vm_list) {
                int idx;
                LIST_HEAD(invalid_list);

                /*
                 * Never scan more than sc->nr_to_scan VM instances.
                 * Will not hit this condition practically since we do not try
                 * to shrink more than one VM and it is very unlikely to see
                 * !n_used_mmu_pages so many times.
                 */
                if (!nr_to_scan--)
                        break;
                /*
                 * n_used_mmu_pages is accessed without holding kvm->mmu_lock
                 * here. We may skip a VM instance errorneosly, but we do not
                 * want to shrink a VM that only started to populate its MMU
                 * anyway.
                 */
                if (!kvm->arch.n_used_mmu_pages &&
                    !kvm_has_zapped_obsolete_pages(kvm))
                        continue;

                idx = srcu_read_lock(&kvm->srcu);
                write_lock(&kvm->mmu_lock);

                if (kvm_has_zapped_obsolete_pages(kvm)) {
                        kvm_mmu_commit_zap_page(kvm,
                              &kvm->arch.zapped_obsolete_pages);
                        goto unlock;
                }

                freed = kvm_mmu_zap_oldest_mmu_pages(kvm, sc->nr_to_scan);

unlock:
                write_unlock(&kvm->mmu_lock);
                srcu_read_unlock(&kvm->srcu, idx);

                /*
                 * unfair on small ones
                 * per-vm shrinkers cry out
                 * sadness comes quickly
                 */
                list_move_tail(&kvm->vm_list, &vm_list);
                break;
        }

        mutex_unlock(&kvm_lock);
        return freed;
}

static unsigned long
mmu_shrink_count(struct shrinker *shrink, struct shrink_control *sc)
{
        return percpu_counter_read_positive(&kvm_total_used_mmu_pages);
}

static struct shrinker mmu_shrinker = {
        .count_objects = mmu_shrink_count,
        .scan_objects = mmu_shrink_scan,
        .seeks = DEFAULT_SEEKS * 10,
};

static void mmu_destroy_caches(void)
{
        kmem_cache_destroy(pte_list_desc_cache);
        kmem_cache_destroy(mmu_page_header_cache);
}

static bool get_nx_auto_mode(void)
{
        /* Return true when CPU has the bug, and mitigations are ON */
        return boot_cpu_has_bug(X86_BUG_ITLB_MULTIHIT) && !cpu_mitigations_off();
}

static void __set_nx_huge_pages(bool val)
{
        nx_huge_pages = itlb_multihit_kvm_mitigation = val;
}

static int set_nx_huge_pages(const char *val, const struct kernel_param *kp)
{
        bool old_val = nx_huge_pages;
        bool new_val;

        /* In "auto" mode deploy workaround only if CPU has the bug. */
        if (sysfs_streq(val, "off"))
                new_val = 0;
        else if (sysfs_streq(val, "force"))
                new_val = 1;
        else if (sysfs_streq(val, "auto"))
                new_val = get_nx_auto_mode();
        else if (strtobool(val, &new_val) < 0)
                return -EINVAL;

        __set_nx_huge_pages(new_val);

        if (new_val != old_val) {
                struct kvm *kvm;

                mutex_lock(&kvm_lock);

                list_for_each_entry(kvm, &vm_list, vm_list) {
                        mutex_lock(&kvm->slots_lock);
                        kvm_mmu_zap_all_fast(kvm);
                        mutex_unlock(&kvm->slots_lock);

                        wake_up_process(kvm->arch.nx_huge_page_recovery_thread);
                }
                mutex_unlock(&kvm_lock);
        }

        return 0;
}

/*
 * nx_huge_pages needs to be resolved to true/false when kvm.ko is loaded, as
 * its default value of -1 is technically undefined behavior for a boolean.
 * Forward the module init call to SPTE code so that it too can handle module
 * params that need to be resolved/snapshot.
 */
void __init kvm_mmu_x86_module_init(void)
{
        if (nx_huge_pages == -1)
                __set_nx_huge_pages(get_nx_auto_mode());

        /*
         * Snapshot userspace's desire to enable the TDP MMU. Whether or not the
         * TDP MMU is actually enabled is determined in kvm_configure_mmu()
         * when the vendor module is loaded.
         */
        tdp_mmu_allowed = tdp_mmu_enabled;

        kvm_mmu_spte_module_init();
}

/*
 * The bulk of the MMU initialization is deferred until the vendor module is
 * loaded as many of the masks/values may be modified by VMX or SVM, i.e. need
 * to be reset when a potentially different vendor module is loaded.
 */
int kvm_mmu_vendor_module_init(void)
{
        int ret = -ENOMEM;

        /*
         * MMU roles use union aliasing which is, generally speaking, an
         * undefined behavior. However, we supposedly know how compilers behave
         * and the current status quo is unlikely to change. Guardians below are
         * supposed to let us know if the assumption becomes false.
         */
        BUILD_BUG_ON(sizeof(union kvm_mmu_page_role) != sizeof(u32));
        BUILD_BUG_ON(sizeof(union kvm_mmu_extended_role) != sizeof(u32));
        BUILD_BUG_ON(sizeof(union kvm_cpu_role) != sizeof(u64));

        kvm_mmu_reset_all_pte_masks();

        pte_list_desc_cache = kmem_cache_create("pte_list_desc",
                                            sizeof(struct pte_list_desc),
                                            0, SLAB_ACCOUNT, NULL);
        if (!pte_list_desc_cache)
                goto out;

        mmu_page_header_cache = kmem_cache_create("kvm_mmu_page_header",
                                                  sizeof(struct kvm_mmu_page),
                                                  0, SLAB_ACCOUNT, NULL);
        if (!mmu_page_header_cache)
                goto out;

        if (percpu_counter_init(&kvm_total_used_mmu_pages, 0, GFP_KERNEL))
                goto out;

        ret = register_shrinker(&mmu_shrinker, "x86-mmu");
        if (ret)
                goto out_shrinker;

        return 0;

out_shrinker:
        percpu_counter_destroy(&kvm_total_used_mmu_pages);
out:
        mmu_destroy_caches();
        return ret;
}

void kvm_mmu_destroy(struct kvm_vcpu *vcpu)
{
        kvm_mmu_unload(vcpu);
        free_mmu_pages(&vcpu->arch.root_mmu);
        free_mmu_pages(&vcpu->arch.guest_mmu);
        mmu_free_memory_caches(vcpu);
}

void kvm_mmu_vendor_module_exit(void)
{
        mmu_destroy_caches();
        percpu_counter_destroy(&kvm_total_used_mmu_pages);
        unregister_shrinker(&mmu_shrinker);
}

/*
 * Calculate the effective recovery period, accounting for '0' meaning "let KVM
 * select a halving time of 1 hour".  Returns true if recovery is enabled.
 */
static bool calc_nx_huge_pages_recovery_period(uint *period)
{
        /*
         * Use READ_ONCE to get the params, this may be called outside of the
         * param setters, e.g. by the kthread to compute its next timeout.
         */
        bool enabled = READ_ONCE(nx_huge_pages);
        uint ratio = READ_ONCE(nx_huge_pages_recovery_ratio);

        if (!enabled || !ratio)
                return false;

        *period = READ_ONCE(nx_huge_pages_recovery_period_ms);
        if (!*period) {
                /* Make sure the period is not less than one second.  */
                ratio = min(ratio, 3600u);
                *period = 60 * 60 * 1000 / ratio;
        }
        return true;
}

static int set_nx_huge_pages_recovery_param(const char *val, const struct kernel_param *kp)
{
        bool was_recovery_enabled, is_recovery_enabled;
        uint old_period, new_period;
        int err;

        was_recovery_enabled = calc_nx_huge_pages_recovery_period(&old_period);

        err = param_set_uint(val, kp);
        if (err)
                return err;

        is_recovery_enabled = calc_nx_huge_pages_recovery_period(&new_period);

        if (is_recovery_enabled &&
            (!was_recovery_enabled || old_period > new_period)) {
                struct kvm *kvm;

                mutex_lock(&kvm_lock);

                list_for_each_entry(kvm, &vm_list, vm_list)
                        wake_up_process(kvm->arch.nx_huge_page_recovery_thread);

                mutex_unlock(&kvm_lock);
        }

        return err;
}

static void kvm_recover_nx_huge_pages(struct kvm *kvm)
{
        unsigned long nx_lpage_splits = kvm->stat.nx_lpage_splits;
        struct kvm_memory_slot *slot;
        int rcu_idx;
        struct kvm_mmu_page *sp;
        unsigned int ratio;
        LIST_HEAD(invalid_list);
        bool flush = false;
        ulong to_zap;

        rcu_idx = srcu_read_lock(&kvm->srcu);
        write_lock(&kvm->mmu_lock);

        /*
         * Zapping TDP MMU shadow pages, including the remote TLB flush, must
         * be done under RCU protection, because the pages are freed via RCU
         * callback.
         */
        rcu_read_lock();

        ratio = READ_ONCE(nx_huge_pages_recovery_ratio);
        to_zap = ratio ? DIV_ROUND_UP(nx_lpage_splits, ratio) : 0;
        for ( ; to_zap; --to_zap) {
                if (list_empty(&kvm->arch.possible_nx_huge_pages))
                        break;

                /*
                 * We use a separate list instead of just using active_mmu_pages
                 * because the number of shadow pages that be replaced with an
                 * NX huge page is expected to be relatively small compared to
                 * the total number of shadow pages.  And because the TDP MMU
                 * doesn't use active_mmu_pages.
                 */
                sp = list_first_entry(&kvm->arch.possible_nx_huge_pages,
                                      struct kvm_mmu_page,
                                      possible_nx_huge_page_link);
                WARN_ON_ONCE(!sp->nx_huge_page_disallowed);
                WARN_ON_ONCE(!sp->role.direct);

                /*
                 * Unaccount and do not attempt to recover any NX Huge Pages
                 * that are being dirty tracked, as they would just be faulted
                 * back in as 4KiB pages. The NX Huge Pages in this slot will be
                 * recovered, along with all the other huge pages in the slot,
                 * when dirty logging is disabled.
                 *
                 * Since gfn_to_memslot() is relatively expensive, it helps to
                 * skip it if it the test cannot possibly return true.  On the
                 * other hand, if any memslot has logging enabled, chances are
                 * good that all of them do, in which case unaccount_nx_huge_page()
                 * is much cheaper than zapping the page.
                 *
                 * If a memslot update is in progress, reading an incorrect value
                 * of kvm->nr_memslots_dirty_logging is not a problem: if it is
                 * becoming zero, gfn_to_memslot() will be done unnecessarily; if
                 * it is becoming nonzero, the page will be zapped unnecessarily.
                 * Either way, this only affects efficiency in racy situations,
                 * and not correctness.
                 */
                slot = NULL;
                if (atomic_read(&kvm->nr_memslots_dirty_logging)) {
                        slot = gfn_to_memslot(kvm, sp->gfn);
                        WARN_ON_ONCE(!slot);
                }

                if (slot && kvm_slot_dirty_track_enabled(slot))
                        unaccount_nx_huge_page(kvm, sp);
                else if (is_tdp_mmu_page(sp))
                        flush |= kvm_tdp_mmu_zap_sp(kvm, sp);
                else
                        kvm_mmu_prepare_zap_page(kvm, sp, &invalid_list);
                WARN_ON_ONCE(sp->nx_huge_page_disallowed);

                if (need_resched() || rwlock_needbreak(&kvm->mmu_lock)) {
                        kvm_mmu_remote_flush_or_zap(kvm, &invalid_list, flush);
                        rcu_read_unlock();

                        cond_resched_rwlock_write(&kvm->mmu_lock);
                        flush = false;

                        rcu_read_lock();
                }
        }
        kvm_mmu_remote_flush_or_zap(kvm, &invalid_list, flush);

        rcu_read_unlock();

        write_unlock(&kvm->mmu_lock);
        srcu_read_unlock(&kvm->srcu, rcu_idx);
}

static long get_nx_huge_page_recovery_timeout(u64 start_time)
{
        bool enabled;
        uint period;

        enabled = calc_nx_huge_pages_recovery_period(&period);

        return enabled ? start_time + msecs_to_jiffies(period) - get_jiffies_64()
                       : MAX_SCHEDULE_TIMEOUT;
}

static int kvm_nx_huge_page_recovery_worker(struct kvm *kvm, uintptr_t data)
{
        u64 start_time;
        long remaining_time;

        while (true) {
                start_time = get_jiffies_64();
                remaining_time = get_nx_huge_page_recovery_timeout(start_time);

                set_current_state(TASK_INTERRUPTIBLE);
                while (!kthread_should_stop() && remaining_time > 0) {
                        schedule_timeout(remaining_time);
                        remaining_time = get_nx_huge_page_recovery_timeout(start_time);
                        set_current_state(TASK_INTERRUPTIBLE);
                }

                set_current_state(TASK_RUNNING);

                if (kthread_should_stop())
                        return 0;

                kvm_recover_nx_huge_pages(kvm);
        }
}

int kvm_mmu_post_init_vm(struct kvm *kvm)
{
        int err;

        err = kvm_vm_create_worker_thread(kvm, kvm_nx_huge_page_recovery_worker, 0,
                                          "kvm-nx-lpage-recovery",
                                          &kvm->arch.nx_huge_page_recovery_thread);
        if (!err)
                kthread_unpark(kvm->arch.nx_huge_page_recovery_thread);

        return err;
}

void kvm_mmu_pre_destroy_vm(struct kvm *kvm)
{
        if (kvm->arch.nx_huge_page_recovery_thread)
                kthread_stop(kvm->arch.nx_huge_page_recovery_thread);
}