arch/mips/kvm/mmu.c

   1 /*
   2  * This file is subject to the terms and conditions of the GNU General Public
   3  * License.  See the file "COPYING" in the main directory of this archive
   4  * for more details.
   5  *
   6  * KVM/MIPS MMU handling in the KVM module.
   7  *
   8  * Copyright (C) 2012  MIPS Technologies, Inc.  All rights reserved.
   9  * Authors: Sanjay Lal <sanjayl@kymasys.com>
  10  */
  11
  12 #include <linux/highmem.h>
  13 #include <linux/kvm_host.h>
  14 #include <linux/uaccess.h>
  15 #include <asm/mmu_context.h>
  16 #include <asm/pgalloc.h>
  17
  18 /*
  19  * KVM_MMU_CACHE_MIN_PAGES is the number of GPA page table translation levels
  20  * for which pages need to be cached.
  21  */
  22 #if defined(__PAGETABLE_PMD_FOLDED)
  23 #define KVM_MMU_CACHE_MIN_PAGES 1
  24 #else
  25 #define KVM_MMU_CACHE_MIN_PAGES 2
  26 #endif
  27
  28 void kvm_mmu_free_memory_caches(struct kvm_vcpu *vcpu)
  29 {
  30         kvm_mmu_free_memory_cache(&vcpu->arch.mmu_page_cache);
  31 }
  32
  33 /**
  34  * kvm_pgd_init() - Initialise KVM GPA page directory.
  35  * @page:       Pointer to page directory (PGD) for KVM GPA.
  36  *
  37  * Initialise a KVM GPA page directory with pointers to the invalid table, i.e.
  38  * representing no mappings. This is similar to pgd_init(), however it
  39  * initialises all the page directory pointers, not just the ones corresponding
  40  * to the userland address space (since it is for the guest physical address
  41  * space rather than a virtual address space).
  42  */
  43 static void kvm_pgd_init(void *page)
  44 {
  45         unsigned long *p, *end;
  46         unsigned long entry;
  47
  48 #ifdef __PAGETABLE_PMD_FOLDED
  49         entry = (unsigned long)invalid_pte_table;
  50 #else
  51         entry = (unsigned long)invalid_pmd_table;
  52 #endif
  53
  54         p = (unsigned long *)page;
  55         end = p + PTRS_PER_PGD;
  56
  57         do {
  58                 p[0] = entry;
  59                 p[1] = entry;
  60                 p[2] = entry;
  61                 p[3] = entry;
  62                 p[4] = entry;
  63                 p += 8;
  64                 p[-3] = entry;
  65                 p[-2] = entry;
  66                 p[-1] = entry;
  67         } while (p != end);
  68 }
  69
  70 /**
  71  * kvm_pgd_alloc() - Allocate and initialise a KVM GPA page directory.
  72  *
  73  * Allocate a blank KVM GPA page directory (PGD) for representing guest physical
  74  * to host physical page mappings.
  75  *
  76  * Returns:     Pointer to new KVM GPA page directory.
  77  *              NULL on allocation failure.
  78  */
  79 pgd_t *kvm_pgd_alloc(void)
  80 {
  81         pgd_t *ret;
  82
  83         ret = (pgd_t *)__get_free_pages(GFP_KERNEL, PGD_ORDER);
  84         if (ret)
  85                 kvm_pgd_init(ret);
  86
  87         return ret;
  88 }
  89
  90 /**
  91  * kvm_mips_walk_pgd() - Walk page table with optional allocation.
  92  * @pgd:        Page directory pointer.
  93  * @addr:       Address to index page table using.
  94  * @cache:      MMU page cache to allocate new page tables from, or NULL.
  95  *
  96  * Walk the page tables pointed to by @pgd to find the PTE corresponding to the
  97  * address @addr. If page tables don't exist for @addr, they will be created
  98  * from the MMU cache if @cache is not NULL.
  99  *
 100  * Returns:     Pointer to pte_t corresponding to @addr.
 101  *              NULL if a page table doesn't exist for @addr and !@cache.
 102  *              NULL if a page table allocation failed.
 103  */
 104 static pte_t *kvm_mips_walk_pgd(pgd_t *pgd, struct kvm_mmu_memory_cache *cache,
 105                                 unsigned long addr)
 106 {
 107         p4d_t *p4d;
 108         pud_t *pud;
 109         pmd_t *pmd;
 110
 111         pgd += pgd_index(addr);
 112         if (pgd_none(*pgd)) {
 113                 /* Not used on MIPS yet */
 114                 BUG();
 115                 return NULL;
 116         }
 117         p4d = p4d_offset(pgd, addr);
 118         pud = pud_offset(p4d, addr);
 119         if (pud_none(*pud)) {
 120                 pmd_t *new_pmd;
 121
 122                 if (!cache)
 123                         return NULL;
 124                 new_pmd = kvm_mmu_memory_cache_alloc(cache);
 125                 pmd_init((unsigned long)new_pmd,
 126                          (unsigned long)invalid_pte_table);
 127                 pud_populate(NULL, pud, new_pmd);
 128         }
 129         pmd = pmd_offset(pud, addr);
 130         if (pmd_none(*pmd)) {
 131                 pte_t *new_pte;
 132
 133                 if (!cache)
 134                         return NULL;
 135                 new_pte = kvm_mmu_memory_cache_alloc(cache);
 136                 clear_page(new_pte);
 137                 pmd_populate_kernel(NULL, pmd, new_pte);
 138         }
 139         return pte_offset_kernel(pmd, addr);
 140 }
 141
 142 /* Caller must hold kvm->mm_lock */
 143 static pte_t *kvm_mips_pte_for_gpa(struct kvm *kvm,
 144                                    struct kvm_mmu_memory_cache *cache,
 145                                    unsigned long addr)
 146 {
 147         return kvm_mips_walk_pgd(kvm->arch.gpa_mm.pgd, cache, addr);
 148 }
 149
 150 /*
 151  * kvm_mips_flush_gpa_{pte,pmd,pud,pgd,pt}.
 152  * Flush a range of guest physical address space from the VM's GPA page tables.
 153  */
 154
 155 static bool kvm_mips_flush_gpa_pte(pte_t *pte, unsigned long start_gpa,
 156                                    unsigned long end_gpa)
 157 {
 158         int i_min = pte_index(start_gpa);
 159         int i_max = pte_index(end_gpa);
 160         bool safe_to_remove = (i_min == 0 && i_max == PTRS_PER_PTE - 1);
 161         int i;
 162
 163         for (i = i_min; i <= i_max; ++i) {
 164                 if (!pte_present(pte[i]))
 165                         continue;
 166
 167                 set_pte(pte + i, __pte(0));
 168         }
 169         return safe_to_remove;
 170 }
 171
 172 static bool kvm_mips_flush_gpa_pmd(pmd_t *pmd, unsigned long start_gpa,
 173                                    unsigned long end_gpa)
 174 {
 175         pte_t *pte;
 176         unsigned long end = ~0ul;
 177         int i_min = pmd_index(start_gpa);
 178         int i_max = pmd_index(end_gpa);
 179         bool safe_to_remove = (i_min == 0 && i_max == PTRS_PER_PMD - 1);
 180         int i;
 181
 182         for (i = i_min; i <= i_max; ++i, start_gpa = 0) {
 183                 if (!pmd_present(pmd[i]))
 184                         continue;
 185
 186                 pte = pte_offset_kernel(pmd + i, 0);
 187                 if (i == i_max)
 188                         end = end_gpa;
 189
 190                 if (kvm_mips_flush_gpa_pte(pte, start_gpa, end)) {
 191                         pmd_clear(pmd + i);
 192                         pte_free_kernel(NULL, pte);
 193                 } else {
 194                         safe_to_remove = false;
 195                 }
 196         }
 197         return safe_to_remove;
 198 }
 199
 200 static bool kvm_mips_flush_gpa_pud(pud_t *pud, unsigned long start_gpa,
 201                                    unsigned long end_gpa)
 202 {
 203         pmd_t *pmd;
 204         unsigned long end = ~0ul;
 205         int i_min = pud_index(start_gpa);
 206         int i_max = pud_index(end_gpa);
 207         bool safe_to_remove = (i_min == 0 && i_max == PTRS_PER_PUD - 1);
 208         int i;
 209
 210         for (i = i_min; i <= i_max; ++i, start_gpa = 0) {
 211                 if (!pud_present(pud[i]))
 212                         continue;
 213
 214                 pmd = pmd_offset(pud + i, 0);
 215                 if (i == i_max)
 216                         end = end_gpa;
 217
 218                 if (kvm_mips_flush_gpa_pmd(pmd, start_gpa, end)) {
 219                         pud_clear(pud + i);
 220                         pmd_free(NULL, pmd);
 221                 } else {
 222                         safe_to_remove = false;
 223                 }
 224         }
 225         return safe_to_remove;
 226 }
 227
 228 static bool kvm_mips_flush_gpa_pgd(pgd_t *pgd, unsigned long start_gpa,
 229                                    unsigned long end_gpa)
 230 {
 231         p4d_t *p4d;
 232         pud_t *pud;
 233         unsigned long end = ~0ul;
 234         int i_min = pgd_index(start_gpa);
 235         int i_max = pgd_index(end_gpa);
 236         bool safe_to_remove = (i_min == 0 && i_max == PTRS_PER_PGD - 1);
 237         int i;
 238
 239         for (i = i_min; i <= i_max; ++i, start_gpa = 0) {
 240                 if (!pgd_present(pgd[i]))
 241                         continue;
 242
 243                 p4d = p4d_offset(pgd, 0);
 244                 pud = pud_offset(p4d + i, 0);
 245                 if (i == i_max)
 246                         end = end_gpa;
 247
 248                 if (kvm_mips_flush_gpa_pud(pud, start_gpa, end)) {
 249                         pgd_clear(pgd + i);
 250                         pud_free(NULL, pud);
 251                 } else {
 252                         safe_to_remove = false;
 253                 }
 254         }
 255         return safe_to_remove;
 256 }
 257
 258 /**
 259  * kvm_mips_flush_gpa_pt() - Flush a range of guest physical addresses.
 260  * @kvm:        KVM pointer.
 261  * @start_gfn:  Guest frame number of first page in GPA range to flush.
 262  * @end_gfn:    Guest frame number of last page in GPA range to flush.
 263  *
 264  * Flushes a range of GPA mappings from the GPA page tables.
 265  *
 266  * The caller must hold the @kvm->mmu_lock spinlock.
 267  *
 268  * Returns:     Whether its safe to remove the top level page directory because
 269  *              all lower levels have been removed.
 270  */
 271 bool kvm_mips_flush_gpa_pt(struct kvm *kvm, gfn_t start_gfn, gfn_t end_gfn)
 272 {
 273         return kvm_mips_flush_gpa_pgd(kvm->arch.gpa_mm.pgd,
 274                                       start_gfn << PAGE_SHIFT,
 275                                       end_gfn << PAGE_SHIFT);
 276 }
 277
 278 #define BUILD_PTE_RANGE_OP(name, op)                                    \
 279 static int kvm_mips_##name##_pte(pte_t *pte, unsigned long start,       \
 280                                  unsigned long end)                     \
 281 {                                                                       \
 282         int ret = 0;                                                    \
 283         int i_min = pte_index(start);                           \
 284         int i_max = pte_index(end);                                     \
 285         int i;                                                          \
 286         pte_t old, new;                                                 \
 287                                                                         \
 288         for (i = i_min; i <= i_max; ++i) {                              \
 289                 if (!pte_present(pte[i]))                               \
 290                         continue;                                       \
 291                                                                         \
 292                 old = pte[i];                                           \
 293                 new = op(old);                                          \
 294                 if (pte_val(new) == pte_val(old))                       \
 295                         continue;                                       \
 296                 set_pte(pte + i, new);                                  \
 297                 ret = 1;                                                \
 298         }                                                               \
 299         return ret;                                                     \
 300 }                                                                       \
 301                                                                         \
 302 /* returns true if anything was done */                                 \
 303 static int kvm_mips_##name##_pmd(pmd_t *pmd, unsigned long start,       \
 304                                  unsigned long end)                     \
 305 {                                                                       \
 306         int ret = 0;                                                    \
 307         pte_t *pte;                                                     \
 308         unsigned long cur_end = ~0ul;                                   \
 309         int i_min = pmd_index(start);                           \
 310         int i_max = pmd_index(end);                                     \
 311         int i;                                                          \
 312                                                                         \
 313         for (i = i_min; i <= i_max; ++i, start = 0) {                   \
 314                 if (!pmd_present(pmd[i]))                               \
 315                         continue;                                       \
 316                                                                         \
 317                 pte = pte_offset_kernel(pmd + i, 0);                            \
 318                 if (i == i_max)                                         \
 319                         cur_end = end;                                  \
 320                                                                         \
 321                 ret |= kvm_mips_##name##_pte(pte, start, cur_end);      \
 322         }                                                               \
 323         return ret;                                                     \
 324 }                                                                       \
 325                                                                         \
 326 static int kvm_mips_##name##_pud(pud_t *pud, unsigned long start,       \
 327                                  unsigned long end)                     \
 328 {                                                                       \
 329         int ret = 0;                                                    \
 330         pmd_t *pmd;                                                     \
 331         unsigned long cur_end = ~0ul;                                   \
 332         int i_min = pud_index(start);                           \
 333         int i_max = pud_index(end);                                     \
 334         int i;                                                          \
 335                                                                         \
 336         for (i = i_min; i <= i_max; ++i, start = 0) {                   \
 337                 if (!pud_present(pud[i]))                               \
 338                         continue;                                       \
 339                                                                         \
 340                 pmd = pmd_offset(pud + i, 0);                           \
 341                 if (i == i_max)                                         \
 342                         cur_end = end;                                  \
 343                                                                         \
 344                 ret |= kvm_mips_##name##_pmd(pmd, start, cur_end);      \
 345         }                                                               \
 346         return ret;                                                     \
 347 }                                                                       \
 348                                                                         \
 349 static int kvm_mips_##name##_pgd(pgd_t *pgd, unsigned long start,       \
 350                                  unsigned long end)                     \
 351 {                                                                       \
 352         int ret = 0;                                                    \
 353         p4d_t *p4d;                                                     \
 354         pud_t *pud;                                                     \
 355         unsigned long cur_end = ~0ul;                                   \
 356         int i_min = pgd_index(start);                                   \
 357         int i_max = pgd_index(end);                                     \
 358         int i;                                                          \
 359                                                                         \
 360         for (i = i_min; i <= i_max; ++i, start = 0) {                   \
 361                 if (!pgd_present(pgd[i]))                               \
 362                         continue;                                       \
 363                                                                         \
 364                 p4d = p4d_offset(pgd, 0);                               \
 365                 pud = pud_offset(p4d + i, 0);                           \
 366                 if (i == i_max)                                         \
 367                         cur_end = end;                                  \
 368                                                                         \
 369                 ret |= kvm_mips_##name##_pud(pud, start, cur_end);      \
 370         }                                                               \
 371         return ret;                                                     \
 372 }
 373
 374 /*
 375  * kvm_mips_mkclean_gpa_pt.
 376  * Mark a range of guest physical address space clean (writes fault) in the VM's
 377  * GPA page table to allow dirty page tracking.
 378  */
 379
 380 BUILD_PTE_RANGE_OP(mkclean, pte_mkclean)
 381
 382 /**
 383  * kvm_mips_mkclean_gpa_pt() - Make a range of guest physical addresses clean.
 384  * @kvm:        KVM pointer.
 385  * @start_gfn:  Guest frame number of first page in GPA range to flush.
 386  * @end_gfn:    Guest frame number of last page in GPA range to flush.
 387  *
 388  * Make a range of GPA mappings clean so that guest writes will fault and
 389  * trigger dirty page logging.
 390  *
 391  * The caller must hold the @kvm->mmu_lock spinlock.
 392  *
 393  * Returns:     Whether any GPA mappings were modified, which would require
 394  *              derived mappings (GVA page tables & TLB enties) to be
 395  *              invalidated.
 396  */
 397 int kvm_mips_mkclean_gpa_pt(struct kvm *kvm, gfn_t start_gfn, gfn_t end_gfn)
 398 {
 399         return kvm_mips_mkclean_pgd(kvm->arch.gpa_mm.pgd,
 400                                     start_gfn << PAGE_SHIFT,
 401                                     end_gfn << PAGE_SHIFT);
 402 }
 403
 404 /**
 405  * kvm_arch_mmu_enable_log_dirty_pt_masked() - write protect dirty pages
 406  * @kvm:        The KVM pointer
 407  * @slot:       The memory slot associated with mask
 408  * @gfn_offset: The gfn offset in memory slot
 409  * @mask:       The mask of dirty pages at offset 'gfn_offset' in this memory
 410  *              slot to be write protected
 411  *
 412  * Walks bits set in mask write protects the associated pte's. Caller must
 413  * acquire @kvm->mmu_lock.
 414  */
 415 void kvm_arch_mmu_enable_log_dirty_pt_masked(struct kvm *kvm,
 416                 struct kvm_memory_slot *slot,
 417                 gfn_t gfn_offset, unsigned long mask)
 418 {
 419         gfn_t base_gfn = slot->base_gfn + gfn_offset;
 420         gfn_t start = base_gfn +  __ffs(mask);
 421         gfn_t end = base_gfn + __fls(mask);
 422
 423         kvm_mips_mkclean_gpa_pt(kvm, start, end);
 424 }
 425
 426 /*
 427  * kvm_mips_mkold_gpa_pt.
 428  * Mark a range of guest physical address space old (all accesses fault) in the
 429  * VM's GPA page table to allow detection of commonly used pages.
 430  */
 431
 432 BUILD_PTE_RANGE_OP(mkold, pte_mkold)
 433
 434 static int kvm_mips_mkold_gpa_pt(struct kvm *kvm, gfn_t start_gfn,
 435                                  gfn_t end_gfn)
 436 {
 437         return kvm_mips_mkold_pgd(kvm->arch.gpa_mm.pgd,
 438                                   start_gfn << PAGE_SHIFT,
 439                                   end_gfn << PAGE_SHIFT);
 440 }
 441
 442 bool kvm_unmap_gfn_range(struct kvm *kvm, struct kvm_gfn_range *range)
 443 {
 444         kvm_mips_flush_gpa_pt(kvm, range->start, range->end);
 445         return true;
 446 }
 447
 448 bool kvm_set_spte_gfn(struct kvm *kvm, struct kvm_gfn_range *range)
 449 {
 450         gpa_t gpa = range->start << PAGE_SHIFT;
 451         pte_t hva_pte = range->pte;
 452         pte_t *gpa_pte = kvm_mips_pte_for_gpa(kvm, NULL, gpa);
 453         pte_t old_pte;
 454
 455         if (!gpa_pte)
 456                 return false;
 457
 458         /* Mapping may need adjusting depending on memslot flags */
 459         old_pte = *gpa_pte;
 460         if (range->slot->flags & KVM_MEM_LOG_DIRTY_PAGES && !pte_dirty(old_pte))
 461                 hva_pte = pte_mkclean(hva_pte);
 462         else if (range->slot->flags & KVM_MEM_READONLY)
 463                 hva_pte = pte_wrprotect(hva_pte);
 464
 465         set_pte(gpa_pte, hva_pte);
 466
 467         /* Replacing an absent or old page doesn't need flushes */
 468         if (!pte_present(old_pte) || !pte_young(old_pte))
 469                 return false;
 470
 471         /* Pages swapped, aged, moved, or cleaned require flushes */
 472         return !pte_present(hva_pte) ||
 473                !pte_young(hva_pte) ||
 474                pte_pfn(old_pte) != pte_pfn(hva_pte) ||
 475                (pte_dirty(old_pte) && !pte_dirty(hva_pte));
 476 }
 477
 478 bool kvm_age_gfn(struct kvm *kvm, struct kvm_gfn_range *range)
 479 {
 480         return kvm_mips_mkold_gpa_pt(kvm, range->start, range->end);
 481 }
 482
 483 bool kvm_test_age_gfn(struct kvm *kvm, struct kvm_gfn_range *range)
 484 {
 485         gpa_t gpa = range->start << PAGE_SHIFT;
 486         pte_t *gpa_pte = kvm_mips_pte_for_gpa(kvm, NULL, gpa);
 487
 488         if (!gpa_pte)
 489                 return false;
 490         return pte_young(*gpa_pte);
 491 }
 492
 493 /**
 494  * _kvm_mips_map_page_fast() - Fast path GPA fault handler.
 495  * @vcpu:               VCPU pointer.
 496  * @gpa:                Guest physical address of fault.
 497  * @write_fault:        Whether the fault was due to a write.
 498  * @out_entry:          New PTE for @gpa (written on success unless NULL).
 499  * @out_buddy:          New PTE for @gpa's buddy (written on success unless
 500  *                      NULL).
 501  *
 502  * Perform fast path GPA fault handling, doing all that can be done without
 503  * calling into KVM. This handles marking old pages young (for idle page
 504  * tracking), and dirtying of clean pages (for dirty page logging).
 505  *
 506  * Returns:     0 on success, in which case we can update derived mappings and
 507  *              resume guest execution.
 508  *              -EFAULT on failure due to absent GPA mapping or write to
 509  *              read-only page, in which case KVM must be consulted.
 510  */
 511 static int _kvm_mips_map_page_fast(struct kvm_vcpu *vcpu, unsigned long gpa,
 512                                    bool write_fault,
 513                                    pte_t *out_entry, pte_t *out_buddy)
 514 {
 515         struct kvm *kvm = vcpu->kvm;
 516         gfn_t gfn = gpa >> PAGE_SHIFT;
 517         pte_t *ptep;
 518         kvm_pfn_t pfn = 0;      /* silence bogus GCC warning */
 519         bool pfn_valid = false;
 520         int ret = 0;
 521
 522         spin_lock(&kvm->mmu_lock);
 523
 524         /* Fast path - just check GPA page table for an existing entry */
 525         ptep = kvm_mips_pte_for_gpa(kvm, NULL, gpa);
 526         if (!ptep || !pte_present(*ptep)) {
 527                 ret = -EFAULT;
 528                 goto out;
 529         }
 530
 531         /* Track access to pages marked old */
 532         if (!pte_young(*ptep)) {
 533                 set_pte(ptep, pte_mkyoung(*ptep));
 534                 pfn = pte_pfn(*ptep);
 535                 pfn_valid = true;
 536                 /* call kvm_set_pfn_accessed() after unlock */
 537         }
 538         if (write_fault && !pte_dirty(*ptep)) {
 539                 if (!pte_write(*ptep)) {
 540                         ret = -EFAULT;
 541                         goto out;
 542                 }
 543
 544                 /* Track dirtying of writeable pages */
 545                 set_pte(ptep, pte_mkdirty(*ptep));
 546                 pfn = pte_pfn(*ptep);
 547                 mark_page_dirty(kvm, gfn);
 548                 kvm_set_pfn_dirty(pfn);
 549         }
 550
 551         if (out_entry)
 552                 *out_entry = *ptep;
 553         if (out_buddy)
 554                 *out_buddy = *ptep_buddy(ptep);
 555
 556 out:
 557         spin_unlock(&kvm->mmu_lock);
 558         if (pfn_valid)
 559                 kvm_set_pfn_accessed(pfn);
 560         return ret;
 561 }
 562
 563 /**
 564  * kvm_mips_map_page() - Map a guest physical page.
 565  * @vcpu:               VCPU pointer.
 566  * @gpa:                Guest physical address of fault.
 567  * @write_fault:        Whether the fault was due to a write.
 568  * @out_entry:          New PTE for @gpa (written on success unless NULL).
 569  * @out_buddy:          New PTE for @gpa's buddy (written on success unless
 570  *                      NULL).
 571  *
 572  * Handle GPA faults by creating a new GPA mapping (or updating an existing
 573  * one).
 574  *
 575  * This takes care of marking pages young or dirty (idle/dirty page tracking),
 576  * asking KVM for the corresponding PFN, and creating a mapping in the GPA page
 577  * tables. Derived mappings (GVA page tables and TLBs) must be handled by the
 578  * caller.
 579  *
 580  * Returns:     0 on success, in which case the caller may use the @out_entry
 581  *              and @out_buddy PTEs to update derived mappings and resume guest
 582  *              execution.
 583  *              -EFAULT if there is no memory region at @gpa or a write was
 584  *              attempted to a read-only memory region. This is usually handled
 585  *              as an MMIO access.
 586  */
 587 static int kvm_mips_map_page(struct kvm_vcpu *vcpu, unsigned long gpa,
 588                              bool write_fault,
 589                              pte_t *out_entry, pte_t *out_buddy)
 590 {
 591         struct kvm *kvm = vcpu->kvm;
 592         struct kvm_mmu_memory_cache *memcache = &vcpu->arch.mmu_page_cache;
 593         gfn_t gfn = gpa >> PAGE_SHIFT;
 594         int srcu_idx, err;
 595         kvm_pfn_t pfn;
 596         pte_t *ptep, entry, old_pte;
 597         bool writeable;
 598         unsigned long prot_bits;
 599         unsigned long mmu_seq;
 600
 601         /* Try the fast path to handle old / clean pages */
 602         srcu_idx = srcu_read_lock(&kvm->srcu);
 603         err = _kvm_mips_map_page_fast(vcpu, gpa, write_fault, out_entry,
 604                                       out_buddy);
 605         if (!err)
 606                 goto out;
 607
 608         /* We need a minimum of cached pages ready for page table creation */
 609         err = kvm_mmu_topup_memory_cache(memcache, KVM_MMU_CACHE_MIN_PAGES);
 610         if (err)
 611                 goto out;
 612
 613 retry:
 614         /*
 615          * Used to check for invalidations in progress, of the pfn that is
 616          * returned by pfn_to_pfn_prot below.
 617          */
 618         mmu_seq = kvm->mmu_notifier_seq;
 619         /*
 620          * Ensure the read of mmu_notifier_seq isn't reordered with PTE reads in
 621          * gfn_to_pfn_prot() (which calls get_user_pages()), so that we don't
 622          * risk the page we get a reference to getting unmapped before we have a
 623          * chance to grab the mmu_lock without mmu_notifier_retry() noticing.
 624          *
 625          * This smp_rmb() pairs with the effective smp_wmb() of the combination
 626          * of the pte_unmap_unlock() after the PTE is zapped, and the
 627          * spin_lock() in kvm_mmu_notifier_invalidate_<page|range_end>() before
 628          * mmu_notifier_seq is incremented.
 629          */
 630         smp_rmb();
 631
 632         /* Slow path - ask KVM core whether we can access this GPA */
 633         pfn = gfn_to_pfn_prot(kvm, gfn, write_fault, &writeable);
 634         if (is_error_noslot_pfn(pfn)) {
 635                 err = -EFAULT;
 636                 goto out;
 637         }
 638
 639         spin_lock(&kvm->mmu_lock);
 640         /* Check if an invalidation has taken place since we got pfn */
 641         if (mmu_notifier_retry(kvm, mmu_seq)) {
 642                 /*
 643                  * This can happen when mappings are changed asynchronously, but
 644                  * also synchronously if a COW is triggered by
 645                  * gfn_to_pfn_prot().
 646                  */
 647                 spin_unlock(&kvm->mmu_lock);
 648                 kvm_release_pfn_clean(pfn);
 649                 goto retry;
 650         }
 651
 652         /* Ensure page tables are allocated */
 653         ptep = kvm_mips_pte_for_gpa(kvm, memcache, gpa);
 654
 655         /* Set up the PTE */
 656         prot_bits = _PAGE_PRESENT | __READABLE | _page_cachable_default;
 657         if (writeable) {
 658                 prot_bits |= _PAGE_WRITE;
 659                 if (write_fault) {
 660                         prot_bits |= __WRITEABLE;
 661                         mark_page_dirty(kvm, gfn);
 662                         kvm_set_pfn_dirty(pfn);
 663                 }
 664         }
 665         entry = pfn_pte(pfn, __pgprot(prot_bits));
 666
 667         /* Write the PTE */
 668         old_pte = *ptep;
 669         set_pte(ptep, entry);
 670
 671         err = 0;
 672         if (out_entry)
 673                 *out_entry = *ptep;
 674         if (out_buddy)
 675                 *out_buddy = *ptep_buddy(ptep);
 676
 677         spin_unlock(&kvm->mmu_lock);
 678         kvm_release_pfn_clean(pfn);
 679         kvm_set_pfn_accessed(pfn);
 680 out:
 681         srcu_read_unlock(&kvm->srcu, srcu_idx);
 682         return err;
 683 }
 684
 685 int kvm_mips_handle_vz_root_tlb_fault(unsigned long badvaddr,
 686                                       struct kvm_vcpu *vcpu,
 687                                       bool write_fault)
 688 {
 689         int ret;
 690
 691         ret = kvm_mips_map_page(vcpu, badvaddr, write_fault, NULL, NULL);
 692         if (ret)
 693                 return ret;
 694
 695         /* Invalidate this entry in the TLB */
 696         return kvm_vz_host_tlb_inv(vcpu, badvaddr);
 697 }
 698
 699 /**
 700  * kvm_mips_migrate_count() - Migrate timer.
 701  * @vcpu:       Virtual CPU.
 702  *
 703  * Migrate CP0_Count hrtimer to the current CPU by cancelling and restarting it
 704  * if it was running prior to being cancelled.
 705  *
 706  * Must be called when the VCPU is migrated to a different CPU to ensure that
 707  * timer expiry during guest execution interrupts the guest and causes the
 708  * interrupt to be delivered in a timely manner.
 709  */
 710 static void kvm_mips_migrate_count(struct kvm_vcpu *vcpu)
 711 {
 712         if (hrtimer_cancel(&vcpu->arch.comparecount_timer))
 713                 hrtimer_restart(&vcpu->arch.comparecount_timer);
 714 }
 715
 716 /* Restore ASID once we are scheduled back after preemption */
 717 void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
 718 {
 719         unsigned long flags;
 720
 721         kvm_debug("%s: vcpu %p, cpu: %d\n", __func__, vcpu, cpu);
 722
 723         local_irq_save(flags);
 724
 725         vcpu->cpu = cpu;
 726         if (vcpu->arch.last_sched_cpu != cpu) {
 727                 kvm_debug("[%d->%d]KVM VCPU[%d] switch\n",
 728                           vcpu->arch.last_sched_cpu, cpu, vcpu->vcpu_id);
 729                 /*
 730                  * Migrate the timer interrupt to the current CPU so that it
 731                  * always interrupts the guest and synchronously triggers a
 732                  * guest timer interrupt.
 733                  */
 734                 kvm_mips_migrate_count(vcpu);
 735         }
 736
 737         /* restore guest state to registers */
 738         kvm_mips_callbacks->vcpu_load(vcpu, cpu);
 739
 740         local_irq_restore(flags);
 741 }
 742
 743 /* ASID can change if another task is scheduled during preemption */
 744 void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
 745 {
 746         unsigned long flags;
 747         int cpu;
 748
 749         local_irq_save(flags);
 750
 751         cpu = smp_processor_id();
 752         vcpu->arch.last_sched_cpu = cpu;
 753         vcpu->cpu = -1;
 754
 755         /* save guest state in registers */
 756         kvm_mips_callbacks->vcpu_put(vcpu, cpu);
 757
 758         local_irq_restore(flags);
 759 }