arch/arm64/kvm/hyp/nvhe/mem_protect.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Copyright (C) 2020 Google LLC
   4  * Author: Quentin Perret <qperret@google.com>
   5  */
   6
   7 #include <linux/kvm_host.h>
   8 #include <asm/kvm_emulate.h>
   9 #include <asm/kvm_hyp.h>
  10 #include <asm/kvm_mmu.h>
  11 #include <asm/kvm_pgtable.h>
  12 #include <asm/stage2_pgtable.h>
  13
  14 #include <hyp/switch.h>
  15
  16 #include <nvhe/gfp.h>
  17 #include <nvhe/memory.h>
  18 #include <nvhe/mem_protect.h>
  19 #include <nvhe/mm.h>
  20
  21 #define KVM_HOST_S2_FLAGS (KVM_PGTABLE_S2_NOFWB | KVM_PGTABLE_S2_IDMAP)
  22
  23 extern unsigned long hyp_nr_cpus;
  24 struct host_kvm host_kvm;
  25
  26 static struct hyp_pool host_s2_pool;
  27
  28 /*
  29  * Copies of the host's CPU features registers holding sanitized values.
  30  */
  31 u64 id_aa64mmfr0_el1_sys_val;
  32 u64 id_aa64mmfr1_el1_sys_val;
  33
  34 const u8 pkvm_hyp_id = 1;
  35
  36 static void *host_s2_zalloc_pages_exact(size_t size)
  37 {
  38         return hyp_alloc_pages(&host_s2_pool, get_order(size));
  39 }
  40
  41 static void *host_s2_zalloc_page(void *pool)
  42 {
  43         return hyp_alloc_pages(pool, 0);
  44 }
  45
  46 static void host_s2_get_page(void *addr)
  47 {
  48         hyp_get_page(&host_s2_pool, addr);
  49 }
  50
  51 static void host_s2_put_page(void *addr)
  52 {
  53         hyp_put_page(&host_s2_pool, addr);
  54 }
  55
  56 static int prepare_s2_pool(void *pgt_pool_base)
  57 {
  58         unsigned long nr_pages, pfn;
  59         int ret;
  60
  61         pfn = hyp_virt_to_pfn(pgt_pool_base);
  62         nr_pages = host_s2_pgtable_pages();
  63         ret = hyp_pool_init(&host_s2_pool, pfn, nr_pages, 0);
  64         if (ret)
  65                 return ret;
  66
  67         host_kvm.mm_ops = (struct kvm_pgtable_mm_ops) {
  68                 .zalloc_pages_exact = host_s2_zalloc_pages_exact,
  69                 .zalloc_page = host_s2_zalloc_page,
  70                 .phys_to_virt = hyp_phys_to_virt,
  71                 .virt_to_phys = hyp_virt_to_phys,
  72                 .page_count = hyp_page_count,
  73                 .get_page = host_s2_get_page,
  74                 .put_page = host_s2_put_page,
  75         };
  76
  77         return 0;
  78 }
  79
  80 static void prepare_host_vtcr(void)
  81 {
  82         u32 parange, phys_shift;
  83
  84         /* The host stage 2 is id-mapped, so use parange for T0SZ */
  85         parange = kvm_get_parange(id_aa64mmfr0_el1_sys_val);
  86         phys_shift = id_aa64mmfr0_parange_to_phys_shift(parange);
  87
  88         host_kvm.arch.vtcr = kvm_get_vtcr(id_aa64mmfr0_el1_sys_val,
  89                                           id_aa64mmfr1_el1_sys_val, phys_shift);
  90 }
  91
  92 static bool host_stage2_force_pte_cb(u64 addr, u64 end, enum kvm_pgtable_prot prot);
  93
  94 int kvm_host_prepare_stage2(void *pgt_pool_base)
  95 {
  96         struct kvm_s2_mmu *mmu = &host_kvm.arch.mmu;
  97         int ret;
  98
  99         prepare_host_vtcr();
 100         hyp_spin_lock_init(&host_kvm.lock);
 101
 102         ret = prepare_s2_pool(pgt_pool_base);
 103         if (ret)
 104                 return ret;
 105
 106         ret = __kvm_pgtable_stage2_init(&host_kvm.pgt, &host_kvm.arch,
 107                                         &host_kvm.mm_ops, KVM_HOST_S2_FLAGS,
 108                                         host_stage2_force_pte_cb);
 109         if (ret)
 110                 return ret;
 111
 112         mmu->pgd_phys = __hyp_pa(host_kvm.pgt.pgd);
 113         mmu->arch = &host_kvm.arch;
 114         mmu->pgt = &host_kvm.pgt;
 115         WRITE_ONCE(mmu->vmid.vmid_gen, 0);
 116         WRITE_ONCE(mmu->vmid.vmid, 0);
 117
 118         return 0;
 119 }
 120
 121 int __pkvm_prot_finalize(void)
 122 {
 123         struct kvm_s2_mmu *mmu = &host_kvm.arch.mmu;
 124         struct kvm_nvhe_init_params *params = this_cpu_ptr(&kvm_init_params);
 125
 126         params->vttbr = kvm_get_vttbr(mmu);
 127         params->vtcr = host_kvm.arch.vtcr;
 128         params->hcr_el2 |= HCR_VM;
 129         kvm_flush_dcache_to_poc(params, sizeof(*params));
 130
 131         write_sysreg(params->hcr_el2, hcr_el2);
 132         __load_stage2(&host_kvm.arch.mmu, &host_kvm.arch);
 133
 134         /*
 135          * Make sure to have an ISB before the TLB maintenance below but only
 136          * when __load_stage2() doesn't include one already.
 137          */
 138         asm(ALTERNATIVE("isb", "nop", ARM64_WORKAROUND_SPECULATIVE_AT));
 139
 140         /* Invalidate stale HCR bits that may be cached in TLBs */
 141         __tlbi(vmalls12e1);
 142         dsb(nsh);
 143         isb();
 144
 145         return 0;
 146 }
 147
 148 static int host_stage2_unmap_dev_all(void)
 149 {
 150         struct kvm_pgtable *pgt = &host_kvm.pgt;
 151         struct memblock_region *reg;
 152         u64 addr = 0;
 153         int i, ret;
 154
 155         /* Unmap all non-memory regions to recycle the pages */
 156         for (i = 0; i < hyp_memblock_nr; i++, addr = reg->base + reg->size) {
 157                 reg = &hyp_memory[i];
 158                 ret = kvm_pgtable_stage2_unmap(pgt, addr, reg->base - addr);
 159                 if (ret)
 160                         return ret;
 161         }
 162         return kvm_pgtable_stage2_unmap(pgt, addr, BIT(pgt->ia_bits) - addr);
 163 }
 164
 165 struct kvm_mem_range {
 166         u64 start;
 167         u64 end;
 168 };
 169
 170 static bool find_mem_range(phys_addr_t addr, struct kvm_mem_range *range)
 171 {
 172         int cur, left = 0, right = hyp_memblock_nr;
 173         struct memblock_region *reg;
 174         phys_addr_t end;
 175
 176         range->start = 0;
 177         range->end = ULONG_MAX;
 178
 179         /* The list of memblock regions is sorted, binary search it */
 180         while (left < right) {
 181                 cur = (left + right) >> 1;
 182                 reg = &hyp_memory[cur];
 183                 end = reg->base + reg->size;
 184                 if (addr < reg->base) {
 185                         right = cur;
 186                         range->end = reg->base;
 187                 } else if (addr >= end) {
 188                         left = cur + 1;
 189                         range->start = end;
 190                 } else {
 191                         range->start = reg->base;
 192                         range->end = end;
 193                         return true;
 194                 }
 195         }
 196
 197         return false;
 198 }
 199
 200 bool addr_is_memory(phys_addr_t phys)
 201 {
 202         struct kvm_mem_range range;
 203
 204         return find_mem_range(phys, &range);
 205 }
 206
 207 static bool is_in_mem_range(u64 addr, struct kvm_mem_range *range)
 208 {
 209         return range->start <= addr && addr < range->end;
 210 }
 211
 212 static bool range_is_memory(u64 start, u64 end)
 213 {
 214         struct kvm_mem_range r;
 215
 216         if (!find_mem_range(start, &r))
 217                 return false;
 218
 219         return is_in_mem_range(end - 1, &r);
 220 }
 221
 222 static inline int __host_stage2_idmap(u64 start, u64 end,
 223                                       enum kvm_pgtable_prot prot)
 224 {
 225         return kvm_pgtable_stage2_map(&host_kvm.pgt, start, end - start, start,
 226                                       prot, &host_s2_pool);
 227 }
 228
 229 /*
 230  * The pool has been provided with enough pages to cover all of memory with
 231  * page granularity, but it is difficult to know how much of the MMIO range
 232  * we will need to cover upfront, so we may need to 'recycle' the pages if we
 233  * run out.
 234  */
 235 #define host_stage2_try(fn, ...)                                        \
 236         ({                                                              \
 237                 int __ret;                                              \
 238                 hyp_assert_lock_held(&host_kvm.lock);                   \
 239                 __ret = fn(__VA_ARGS__);                                \
 240                 if (__ret == -ENOMEM) {                                 \
 241                         __ret = host_stage2_unmap_dev_all();            \
 242                         if (!__ret)                                     \
 243                                 __ret = fn(__VA_ARGS__);                \
 244                 }                                                       \
 245                 __ret;                                                  \
 246          })
 247
 248 static inline bool range_included(struct kvm_mem_range *child,
 249                                   struct kvm_mem_range *parent)
 250 {
 251         return parent->start <= child->start && child->end <= parent->end;
 252 }
 253
 254 static int host_stage2_adjust_range(u64 addr, struct kvm_mem_range *range)
 255 {
 256         struct kvm_mem_range cur;
 257         kvm_pte_t pte;
 258         u32 level;
 259         int ret;
 260
 261         hyp_assert_lock_held(&host_kvm.lock);
 262         ret = kvm_pgtable_get_leaf(&host_kvm.pgt, addr, &pte, &level);
 263         if (ret)
 264                 return ret;
 265
 266         if (kvm_pte_valid(pte))
 267                 return -EAGAIN;
 268
 269         if (pte)
 270                 return -EPERM;
 271
 272         do {
 273                 u64 granule = kvm_granule_size(level);
 274                 cur.start = ALIGN_DOWN(addr, granule);
 275                 cur.end = cur.start + granule;
 276                 level++;
 277         } while ((level < KVM_PGTABLE_MAX_LEVELS) &&
 278                         !(kvm_level_supports_block_mapping(level) &&
 279                           range_included(&cur, range)));
 280
 281         *range = cur;
 282
 283         return 0;
 284 }
 285
 286 int host_stage2_idmap_locked(phys_addr_t addr, u64 size,
 287                              enum kvm_pgtable_prot prot)
 288 {
 289         hyp_assert_lock_held(&host_kvm.lock);
 290
 291         return host_stage2_try(__host_stage2_idmap, addr, addr + size, prot);
 292 }
 293
 294 int host_stage2_set_owner_locked(phys_addr_t addr, u64 size, u8 owner_id)
 295 {
 296         hyp_assert_lock_held(&host_kvm.lock);
 297
 298         return host_stage2_try(kvm_pgtable_stage2_set_owner, &host_kvm.pgt,
 299                                addr, size, &host_s2_pool, owner_id);
 300 }
 301
 302 static bool host_stage2_force_pte_cb(u64 addr, u64 end, enum kvm_pgtable_prot prot)
 303 {
 304         /*
 305          * Block mappings must be used with care in the host stage-2 as a
 306          * kvm_pgtable_stage2_map() operation targeting a page in the range of
 307          * an existing block will delete the block under the assumption that
 308          * mappings in the rest of the block range can always be rebuilt lazily.
 309          * That assumption is correct for the host stage-2 with RWX mappings
 310          * targeting memory or RW mappings targeting MMIO ranges (see
 311          * host_stage2_idmap() below which implements some of the host memory
 312          * abort logic). However, this is not safe for any other mappings where
 313          * the host stage-2 page-table is in fact the only place where this
 314          * state is stored. In all those cases, it is safer to use page-level
 315          * mappings, hence avoiding to lose the state because of side-effects in
 316          * kvm_pgtable_stage2_map().
 317          */
 318         if (range_is_memory(addr, end))
 319                 return prot != PKVM_HOST_MEM_PROT;
 320         else
 321                 return prot != PKVM_HOST_MMIO_PROT;
 322 }
 323
 324 static int host_stage2_idmap(u64 addr)
 325 {
 326         struct kvm_mem_range range;
 327         bool is_memory = find_mem_range(addr, &range);
 328         enum kvm_pgtable_prot prot;
 329         int ret;
 330
 331         prot = is_memory ? PKVM_HOST_MEM_PROT : PKVM_HOST_MMIO_PROT;
 332
 333         hyp_spin_lock(&host_kvm.lock);
 334         ret = host_stage2_adjust_range(addr, &range);
 335         if (ret)
 336                 goto unlock;
 337
 338         ret = host_stage2_idmap_locked(range.start, range.end - range.start, prot);
 339 unlock:
 340         hyp_spin_unlock(&host_kvm.lock);
 341
 342         return ret;
 343 }
 344
 345 static inline bool check_prot(enum kvm_pgtable_prot prot,
 346                               enum kvm_pgtable_prot required,
 347                               enum kvm_pgtable_prot denied)
 348 {
 349         return (prot & (required | denied)) == required;
 350 }
 351
 352 int __pkvm_host_share_hyp(u64 pfn)
 353 {
 354         phys_addr_t addr = hyp_pfn_to_phys(pfn);
 355         enum kvm_pgtable_prot prot, cur;
 356         void *virt = __hyp_va(addr);
 357         enum pkvm_page_state state;
 358         kvm_pte_t pte;
 359         int ret;
 360
 361         if (!addr_is_memory(addr))
 362                 return -EINVAL;
 363
 364         hyp_spin_lock(&host_kvm.lock);
 365         hyp_spin_lock(&pkvm_pgd_lock);
 366
 367         ret = kvm_pgtable_get_leaf(&host_kvm.pgt, addr, &pte, NULL);
 368         if (ret)
 369                 goto unlock;
 370         if (!pte)
 371                 goto map_shared;
 372
 373         /*
 374          * Check attributes in the host stage-2 PTE. We need the page to be:
 375          *  - mapped RWX as we're sharing memory;
 376          *  - not borrowed, as that implies absence of ownership.
 377          * Otherwise, we can't let it got through
 378          */
 379         cur = kvm_pgtable_stage2_pte_prot(pte);
 380         prot = pkvm_mkstate(0, PKVM_PAGE_SHARED_BORROWED);
 381         if (!check_prot(cur, PKVM_HOST_MEM_PROT, prot)) {
 382                 ret = -EPERM;
 383                 goto unlock;
 384         }
 385
 386         state = pkvm_getstate(cur);
 387         if (state == PKVM_PAGE_OWNED)
 388                 goto map_shared;
 389
 390         /*
 391          * Tolerate double-sharing the same page, but this requires
 392          * cross-checking the hypervisor stage-1.
 393          */
 394         if (state != PKVM_PAGE_SHARED_OWNED) {
 395                 ret = -EPERM;
 396                 goto unlock;
 397         }
 398
 399         ret = kvm_pgtable_get_leaf(&pkvm_pgtable, (u64)virt, &pte, NULL);
 400         if (ret)
 401                 goto unlock;
 402
 403         /*
 404          * If the page has been shared with the hypervisor, it must be
 405          * already mapped as SHARED_BORROWED in its stage-1.
 406          */
 407         cur = kvm_pgtable_hyp_pte_prot(pte);
 408         prot = pkvm_mkstate(PAGE_HYP, PKVM_PAGE_SHARED_BORROWED);
 409         if (!check_prot(cur, prot, ~prot))
 410                 ret = -EPERM;
 411         goto unlock;
 412
 413 map_shared:
 414         /*
 415          * If the page is not yet shared, adjust mappings in both page-tables
 416          * while both locks are held.
 417          */
 418         prot = pkvm_mkstate(PAGE_HYP, PKVM_PAGE_SHARED_BORROWED);
 419         ret = pkvm_create_mappings_locked(virt, virt + PAGE_SIZE, prot);
 420         BUG_ON(ret);
 421
 422         prot = pkvm_mkstate(PKVM_HOST_MEM_PROT, PKVM_PAGE_SHARED_OWNED);
 423         ret = host_stage2_idmap_locked(addr, PAGE_SIZE, prot);
 424         BUG_ON(ret);
 425
 426 unlock:
 427         hyp_spin_unlock(&pkvm_pgd_lock);
 428         hyp_spin_unlock(&host_kvm.lock);
 429
 430         return ret;
 431 }
 432
 433 void handle_host_mem_abort(struct kvm_cpu_context *host_ctxt)
 434 {
 435         struct kvm_vcpu_fault_info fault;
 436         u64 esr, addr;
 437         int ret = 0;
 438
 439         esr = read_sysreg_el2(SYS_ESR);
 440         BUG_ON(!__get_fault_info(esr, &fault));
 441
 442         addr = (fault.hpfar_el2 & HPFAR_MASK) << 8;
 443         ret = host_stage2_idmap(addr);
 444         BUG_ON(ret && ret != -EAGAIN);
 445 }