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   1 /*
   2  * Kernel-based Virtual Machine driver for Linux
   3  *
   4  * This module enables machines with Intel VT-x extensions to run virtual
   5  * machines without emulation or binary translation.
   6  *
   7  * MMU support
   8  *
   9  * Copyright (C) 2006 Qumranet, Inc.
  10  *
  11  * Authors:
  12  *   Yaniv Kamay  <yaniv@qumranet.com>
  13  *   Avi Kivity   <avi@qumranet.com>
  14  *
  15  * This work is licensed under the terms of the GNU GPL, version 2.  See
  16  * the COPYING file in the top-level directory.
  17  *
  18  */
  19
  20 /*
  21  * We need the mmu code to access both 32-bit and 64-bit guest ptes,
  22  * so the code in this file is compiled twice, once per pte size.
  23  */
  24
  25 #if PTTYPE == 64
  26         #define pt_element_t u64
  27         #define guest_walker guest_walker64
  28         #define FNAME(name) paging##64_##name
  29         #define PT_BASE_ADDR_MASK PT64_BASE_ADDR_MASK
  30         #define PT_DIR_BASE_ADDR_MASK PT64_DIR_BASE_ADDR_MASK
  31         #define PT_INDEX(addr, level) PT64_INDEX(addr, level)
  32         #define SHADOW_PT_INDEX(addr, level) PT64_INDEX(addr, level)
  33         #define PT_LEVEL_MASK(level) PT64_LEVEL_MASK(level)
  34         #define PT_LEVEL_BITS PT64_LEVEL_BITS
  35         #ifdef CONFIG_X86_64
  36         #define PT_MAX_FULL_LEVELS 4
  37         #else
  38         #define PT_MAX_FULL_LEVELS 2
  39         #endif
  40 #elif PTTYPE == 32
  41         #define pt_element_t u32
  42         #define guest_walker guest_walker32
  43         #define FNAME(name) paging##32_##name
  44         #define PT_BASE_ADDR_MASK PT32_BASE_ADDR_MASK
  45         #define PT_DIR_BASE_ADDR_MASK PT32_DIR_BASE_ADDR_MASK
  46         #define PT_INDEX(addr, level) PT32_INDEX(addr, level)
  47         #define SHADOW_PT_INDEX(addr, level) PT64_INDEX(addr, level)
  48         #define PT_LEVEL_MASK(level) PT32_LEVEL_MASK(level)
  49         #define PT_LEVEL_BITS PT32_LEVEL_BITS
  50         #define PT_MAX_FULL_LEVELS 2
  51 #else
  52         #error Invalid PTTYPE value
  53 #endif
  54
  55 /*
  56  * The guest_walker structure emulates the behavior of the hardware page
  57  * table walker.
  58  */
  59 struct guest_walker {
  60         int level;
  61         gfn_t table_gfn[PT_MAX_FULL_LEVELS];
  62         pt_element_t *table;
  63         pt_element_t pte;
  64         pt_element_t *ptep;
  65         struct page *page;
  66         int index;
  67         pt_element_t inherited_ar;
  68         gfn_t gfn;
  69         u32 error_code;
  70 };
  71
  72 /*
  73  * Fetch a guest pte for a guest virtual address
  74  */
  75 static int FNAME(walk_addr)(struct guest_walker *walker,
  76                             struct kvm_vcpu *vcpu, gva_t addr,
  77                             int write_fault, int user_fault, int fetch_fault)
  78 {
  79         hpa_t hpa;
  80         struct kvm_memory_slot *slot;
  81         pt_element_t *ptep;
  82         pt_element_t root;
  83         gfn_t table_gfn;
  84
  85         pgprintk("%s: addr %lx\n", __FUNCTION__, addr);
  86         walker->level = vcpu->mmu.root_level;
  87         walker->table = NULL;
  88         walker->page = NULL;
  89         walker->ptep = NULL;
  90         root = vcpu->cr3;
  91 #if PTTYPE == 64
  92         if (!is_long_mode(vcpu)) {
  93                 walker->ptep = &vcpu->pdptrs[(addr >> 30) & 3];
  94                 root = *walker->ptep;
  95                 walker->pte = root;
  96                 if (!(root & PT_PRESENT_MASK))
  97                         goto not_present;
  98                 --walker->level;
  99         }
 100 #endif
 101         table_gfn = (root & PT64_BASE_ADDR_MASK) >> PAGE_SHIFT;
 102         walker->table_gfn[walker->level - 1] = table_gfn;
 103         pgprintk("%s: table_gfn[%d] %lx\n", __FUNCTION__,
 104                  walker->level - 1, table_gfn);
 105         slot = gfn_to_memslot(vcpu->kvm, table_gfn);
 106         hpa = safe_gpa_to_hpa(vcpu->kvm, root & PT64_BASE_ADDR_MASK);
 107         walker->page = pfn_to_page(hpa >> PAGE_SHIFT);
 108         walker->table = kmap_atomic(walker->page, KM_USER0);
 109
 110         ASSERT((!is_long_mode(vcpu) && is_pae(vcpu)) ||
 111                (vcpu->cr3 & CR3_NONPAE_RESERVED_BITS) == 0);
 112
 113         walker->inherited_ar = PT_USER_MASK | PT_WRITABLE_MASK;
 114
 115         for (;;) {
 116                 int index = PT_INDEX(addr, walker->level);
 117                 hpa_t paddr;
 118
 119                 ptep = &walker->table[index];
 120                 walker->index = index;
 121                 ASSERT(((unsigned long)walker->table & PAGE_MASK) ==
 122                        ((unsigned long)ptep & PAGE_MASK));
 123
 124                 if (!is_present_pte(*ptep))
 125                         goto not_present;
 126
 127                 if (write_fault && !is_writeble_pte(*ptep))
 128                         if (user_fault || is_write_protection(vcpu))
 129                                 goto access_error;
 130
 131                 if (user_fault && !(*ptep & PT_USER_MASK))
 132                         goto access_error;
 133
 134 #if PTTYPE == 64
 135                 if (fetch_fault && is_nx(vcpu) && (*ptep & PT64_NX_MASK))
 136                         goto access_error;
 137 #endif
 138
 139                 if (!(*ptep & PT_ACCESSED_MASK)) {
 140                         mark_page_dirty(vcpu->kvm, table_gfn);
 141                         *ptep |= PT_ACCESSED_MASK;
 142                 }
 143
 144                 if (walker->level == PT_PAGE_TABLE_LEVEL) {
 145                         walker->gfn = (*ptep & PT_BASE_ADDR_MASK)
 146                                 >> PAGE_SHIFT;
 147                         break;
 148                 }
 149
 150                 if (walker->level == PT_DIRECTORY_LEVEL
 151                     && (*ptep & PT_PAGE_SIZE_MASK)
 152                     && (PTTYPE == 64 || is_pse(vcpu))) {
 153                         walker->gfn = (*ptep & PT_DIR_BASE_ADDR_MASK)
 154                                 >> PAGE_SHIFT;
 155                         walker->gfn += PT_INDEX(addr, PT_PAGE_TABLE_LEVEL);
 156                         break;
 157                 }
 158
 159                 walker->inherited_ar &= walker->table[index];
 160                 table_gfn = (*ptep & PT_BASE_ADDR_MASK) >> PAGE_SHIFT;
 161                 kunmap_atomic(walker->table, KM_USER0);
 162                 paddr = safe_gpa_to_hpa(vcpu->kvm, table_gfn << PAGE_SHIFT);
 163                 walker->page = pfn_to_page(paddr >> PAGE_SHIFT);
 164                 walker->table = kmap_atomic(walker->page, KM_USER0);
 165                 --walker->level;
 166                 walker->table_gfn[walker->level - 1] = table_gfn;
 167                 pgprintk("%s: table_gfn[%d] %lx\n", __FUNCTION__,
 168                          walker->level - 1, table_gfn);
 169         }
 170         walker->pte = *ptep;
 171         if (walker->page)
 172                 walker->ptep = NULL;
 173         if (walker->table)
 174                 kunmap_atomic(walker->table, KM_USER0);
 175         pgprintk("%s: pte %llx\n", __FUNCTION__, (u64)*ptep);
 176         return 1;
 177
 178 not_present:
 179         walker->error_code = 0;
 180         goto err;
 181
 182 access_error:
 183         walker->error_code = PFERR_PRESENT_MASK;
 184
 185 err:
 186         if (write_fault)
 187                 walker->error_code |= PFERR_WRITE_MASK;
 188         if (user_fault)
 189                 walker->error_code |= PFERR_USER_MASK;
 190         if (fetch_fault)
 191                 walker->error_code |= PFERR_FETCH_MASK;
 192         if (walker->table)
 193                 kunmap_atomic(walker->table, KM_USER0);
 194         return 0;
 195 }
 196
 197 static void FNAME(mark_pagetable_dirty)(struct kvm *kvm,
 198                                         struct guest_walker *walker)
 199 {
 200         mark_page_dirty(kvm, walker->table_gfn[walker->level - 1]);
 201 }
 202
 203 static void FNAME(set_pte_common)(struct kvm_vcpu *vcpu,
 204                                   u64 *shadow_pte,
 205                                   gpa_t gaddr,
 206                                   pt_element_t gpte,
 207                                   u64 access_bits,
 208                                   int user_fault,
 209                                   int write_fault,
 210                                   int *ptwrite,
 211                                   struct guest_walker *walker,
 212                                   gfn_t gfn)
 213 {
 214         hpa_t paddr;
 215         int dirty = gpte & PT_DIRTY_MASK;
 216         u64 spte;
 217         int was_rmapped = is_rmap_pte(*shadow_pte);
 218
 219         pgprintk("%s: spte %llx gpte %llx access %llx write_fault %d"
 220                  " user_fault %d gfn %lx\n",
 221                  __FUNCTION__, *shadow_pte, (u64)gpte, access_bits,
 222                  write_fault, user_fault, gfn);
 223
 224         if (write_fault && !dirty) {
 225                 pt_element_t *guest_ent, *tmp = NULL;
 226
 227                 if (walker->ptep)
 228                         guest_ent = walker->ptep;
 229                 else {
 230                         tmp = kmap_atomic(walker->page, KM_USER0);
 231                         guest_ent = &tmp[walker->index];
 232                 }
 233
 234                 *guest_ent |= PT_DIRTY_MASK;
 235                 if (!walker->ptep)
 236                         kunmap_atomic(tmp, KM_USER0);
 237                 dirty = 1;
 238                 FNAME(mark_pagetable_dirty)(vcpu->kvm, walker);
 239         }
 240
 241         /*
 242          * We don't set the accessed bit, since we sometimes want to see
 243          * whether the guest actually used the pte (in order to detect
 244          * demand paging).
 245          */
 246         spte = PT_PRESENT_MASK | PT_DIRTY_MASK;
 247         spte |= gpte & PT64_NX_MASK;
 248         if (!dirty)
 249                 access_bits &= ~PT_WRITABLE_MASK;
 250
 251         paddr = gpa_to_hpa(vcpu->kvm, gaddr & PT64_BASE_ADDR_MASK);
 252
 253         spte |= PT_PRESENT_MASK;
 254         if (access_bits & PT_USER_MASK)
 255                 spte |= PT_USER_MASK;
 256
 257         if (is_error_hpa(paddr)) {
 258                 set_shadow_pte(shadow_pte,
 259                                shadow_trap_nonpresent_pte | PT_SHADOW_IO_MARK);
 260                 return;
 261         }
 262
 263         spte |= paddr;
 264
 265         if ((access_bits & PT_WRITABLE_MASK)
 266             || (write_fault && !is_write_protection(vcpu) && !user_fault)) {
 267                 struct kvm_mmu_page *shadow;
 268
 269                 spte |= PT_WRITABLE_MASK;
 270                 if (user_fault) {
 271                         mmu_unshadow(vcpu->kvm, gfn);
 272                         goto unshadowed;
 273                 }
 274
 275                 shadow = kvm_mmu_lookup_page(vcpu->kvm, gfn);
 276                 if (shadow) {
 277                         pgprintk("%s: found shadow page for %lx, marking ro\n",
 278                                  __FUNCTION__, gfn);
 279                         access_bits &= ~PT_WRITABLE_MASK;
 280                         if (is_writeble_pte(spte)) {
 281                                 spte &= ~PT_WRITABLE_MASK;
 282                                 kvm_x86_ops->tlb_flush(vcpu);
 283                         }
 284                         if (write_fault)
 285                                 *ptwrite = 1;
 286                 }
 287         }
 288
 289 unshadowed:
 290
 291         if (access_bits & PT_WRITABLE_MASK)
 292                 mark_page_dirty(vcpu->kvm, gaddr >> PAGE_SHIFT);
 293
 294         pgprintk("%s: setting spte %llx\n", __FUNCTION__, spte);
 295         set_shadow_pte(shadow_pte, spte);
 296         page_header_update_slot(vcpu->kvm, shadow_pte, gaddr);
 297         if (!was_rmapped)
 298                 rmap_add(vcpu, shadow_pte, (gaddr & PT64_BASE_ADDR_MASK)
 299                          >> PAGE_SHIFT);
 300         if (!ptwrite || !*ptwrite)
 301                 vcpu->last_pte_updated = shadow_pte;
 302 }
 303
 304 static void FNAME(set_pte)(struct kvm_vcpu *vcpu, pt_element_t gpte,
 305                            u64 *shadow_pte, u64 access_bits,
 306                            int user_fault, int write_fault, int *ptwrite,
 307                            struct guest_walker *walker, gfn_t gfn)
 308 {
 309         access_bits &= gpte;
 310         FNAME(set_pte_common)(vcpu, shadow_pte, gpte & PT_BASE_ADDR_MASK,
 311                               gpte, access_bits, user_fault, write_fault,
 312                               ptwrite, walker, gfn);
 313 }
 314
 315 static void FNAME(update_pte)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *page,
 316                               u64 *spte, const void *pte, int bytes,
 317                               int offset_in_pte)
 318 {
 319         pt_element_t gpte;
 320
 321         gpte = *(const pt_element_t *)pte;
 322         if (~gpte & (PT_PRESENT_MASK | PT_ACCESSED_MASK)) {
 323                 if (!offset_in_pte && !is_present_pte(gpte))
 324                         set_shadow_pte(spte, shadow_notrap_nonpresent_pte);
 325                 return;
 326         }
 327         if (bytes < sizeof(pt_element_t))
 328                 return;
 329         pgprintk("%s: gpte %llx spte %p\n", __FUNCTION__, (u64)gpte, spte);
 330         FNAME(set_pte)(vcpu, gpte, spte, PT_USER_MASK | PT_WRITABLE_MASK, 0,
 331                        0, NULL, NULL,
 332                        (gpte & PT_BASE_ADDR_MASK) >> PAGE_SHIFT);
 333 }
 334
 335 static void FNAME(set_pde)(struct kvm_vcpu *vcpu, pt_element_t gpde,
 336                            u64 *shadow_pte, u64 access_bits,
 337                            int user_fault, int write_fault, int *ptwrite,
 338                            struct guest_walker *walker, gfn_t gfn)
 339 {
 340         gpa_t gaddr;
 341
 342         access_bits &= gpde;
 343         gaddr = (gpa_t)gfn << PAGE_SHIFT;
 344         if (PTTYPE == 32 && is_cpuid_PSE36())
 345                 gaddr |= (gpde & PT32_DIR_PSE36_MASK) <<
 346                         (32 - PT32_DIR_PSE36_SHIFT);
 347         FNAME(set_pte_common)(vcpu, shadow_pte, gaddr,
 348                               gpde, access_bits, user_fault, write_fault,
 349                               ptwrite, walker, gfn);
 350 }
 351
 352 /*
 353  * Fetch a shadow pte for a specific level in the paging hierarchy.
 354  */
 355 static u64 *FNAME(fetch)(struct kvm_vcpu *vcpu, gva_t addr,
 356                          struct guest_walker *walker,
 357                          int user_fault, int write_fault, int *ptwrite)
 358 {
 359         hpa_t shadow_addr;
 360         int level;
 361         u64 *shadow_ent;
 362         u64 *prev_shadow_ent = NULL;
 363
 364         if (!is_present_pte(walker->pte))
 365                 return NULL;
 366
 367         shadow_addr = vcpu->mmu.root_hpa;
 368         level = vcpu->mmu.shadow_root_level;
 369         if (level == PT32E_ROOT_LEVEL) {
 370                 shadow_addr = vcpu->mmu.pae_root[(addr >> 30) & 3];
 371                 shadow_addr &= PT64_BASE_ADDR_MASK;
 372                 --level;
 373         }
 374
 375         for (; ; level--) {
 376                 u32 index = SHADOW_PT_INDEX(addr, level);
 377                 struct kvm_mmu_page *shadow_page;
 378                 u64 shadow_pte;
 379                 int metaphysical;
 380                 gfn_t table_gfn;
 381                 unsigned hugepage_access = 0;
 382
 383                 shadow_ent = ((u64 *)__va(shadow_addr)) + index;
 384                 if (is_shadow_present_pte(*shadow_ent)) {
 385                         if (level == PT_PAGE_TABLE_LEVEL)
 386                                 break;
 387                         shadow_addr = *shadow_ent & PT64_BASE_ADDR_MASK;
 388                         prev_shadow_ent = shadow_ent;
 389                         continue;
 390                 }
 391
 392                 if (level == PT_PAGE_TABLE_LEVEL)
 393                         break;
 394
 395                 if (level - 1 == PT_PAGE_TABLE_LEVEL
 396                     && walker->level == PT_DIRECTORY_LEVEL) {
 397                         metaphysical = 1;
 398                         hugepage_access = walker->pte;
 399                         hugepage_access &= PT_USER_MASK | PT_WRITABLE_MASK;
 400                         if (walker->pte & PT64_NX_MASK)
 401                                 hugepage_access |= (1 << 2);
 402                         hugepage_access >>= PT_WRITABLE_SHIFT;
 403                         table_gfn = (walker->pte & PT_BASE_ADDR_MASK)
 404                                 >> PAGE_SHIFT;
 405                 } else {
 406                         metaphysical = 0;
 407                         table_gfn = walker->table_gfn[level - 2];
 408                 }
 409                 shadow_page = kvm_mmu_get_page(vcpu, table_gfn, addr, level-1,
 410                                                metaphysical, hugepage_access,
 411                                                shadow_ent);
 412                 shadow_addr = __pa(shadow_page->spt);
 413                 shadow_pte = shadow_addr | PT_PRESENT_MASK | PT_ACCESSED_MASK
 414                         | PT_WRITABLE_MASK | PT_USER_MASK;
 415                 *shadow_ent = shadow_pte;
 416                 prev_shadow_ent = shadow_ent;
 417         }
 418
 419         if (walker->level == PT_DIRECTORY_LEVEL) {
 420                 FNAME(set_pde)(vcpu, walker->pte, shadow_ent,
 421                                walker->inherited_ar, user_fault, write_fault,
 422                                ptwrite, walker, walker->gfn);
 423         } else {
 424                 ASSERT(walker->level == PT_PAGE_TABLE_LEVEL);
 425                 FNAME(set_pte)(vcpu, walker->pte, shadow_ent,
 426                                walker->inherited_ar, user_fault, write_fault,
 427                                ptwrite, walker, walker->gfn);
 428         }
 429         return shadow_ent;
 430 }
 431
 432 /*
 433  * Page fault handler.  There are several causes for a page fault:
 434  *   - there is no shadow pte for the guest pte
 435  *   - write access through a shadow pte marked read only so that we can set
 436  *     the dirty bit
 437  *   - write access to a shadow pte marked read only so we can update the page
 438  *     dirty bitmap, when userspace requests it
 439  *   - mmio access; in this case we will never install a present shadow pte
 440  *   - normal guest page fault due to the guest pte marked not present, not
 441  *     writable, or not executable
 442  *
 443  *  Returns: 1 if we need to emulate the instruction, 0 otherwise, or
 444  *           a negative value on error.
 445  */
 446 static int FNAME(page_fault)(struct kvm_vcpu *vcpu, gva_t addr,
 447                                u32 error_code)
 448 {
 449         int write_fault = error_code & PFERR_WRITE_MASK;
 450         int user_fault = error_code & PFERR_USER_MASK;
 451         int fetch_fault = error_code & PFERR_FETCH_MASK;
 452         struct guest_walker walker;
 453         u64 *shadow_pte;
 454         int write_pt = 0;
 455         int r;
 456
 457         pgprintk("%s: addr %lx err %x\n", __FUNCTION__, addr, error_code);
 458         kvm_mmu_audit(vcpu, "pre page fault");
 459
 460         r = mmu_topup_memory_caches(vcpu);
 461         if (r)
 462                 return r;
 463
 464         /*
 465          * Look up the shadow pte for the faulting address.
 466          */
 467         r = FNAME(walk_addr)(&walker, vcpu, addr, write_fault, user_fault,
 468                              fetch_fault);
 469
 470         /*
 471          * The page is not mapped by the guest.  Let the guest handle it.
 472          */
 473         if (!r) {
 474                 pgprintk("%s: guest page fault\n", __FUNCTION__);
 475                 inject_page_fault(vcpu, addr, walker.error_code);
 476                 vcpu->last_pt_write_count = 0; /* reset fork detector */
 477                 return 0;
 478         }
 479
 480         shadow_pte = FNAME(fetch)(vcpu, addr, &walker, user_fault, write_fault,
 481                                   &write_pt);
 482         pgprintk("%s: shadow pte %p %llx ptwrite %d\n", __FUNCTION__,
 483                  shadow_pte, *shadow_pte, write_pt);
 484
 485         if (!write_pt)
 486                 vcpu->last_pt_write_count = 0; /* reset fork detector */
 487
 488         /*
 489          * mmio: emulate if accessible, otherwise its a guest fault.
 490          */
 491         if (is_io_pte(*shadow_pte))
 492                 return 1;
 493
 494         ++vcpu->stat.pf_fixed;
 495         kvm_mmu_audit(vcpu, "post page fault (fixed)");
 496
 497         return write_pt;
 498 }
 499
 500 static gpa_t FNAME(gva_to_gpa)(struct kvm_vcpu *vcpu, gva_t vaddr)
 501 {
 502         struct guest_walker walker;
 503         gpa_t gpa = UNMAPPED_GVA;
 504         int r;
 505
 506         r = FNAME(walk_addr)(&walker, vcpu, vaddr, 0, 0, 0);
 507
 508         if (r) {
 509                 gpa = (gpa_t)walker.gfn << PAGE_SHIFT;
 510                 gpa |= vaddr & ~PAGE_MASK;
 511         }
 512
 513         return gpa;
 514 }
 515
 516 static void FNAME(prefetch_page)(struct kvm_vcpu *vcpu,
 517                                  struct kvm_mmu_page *sp)
 518 {
 519         int i;
 520         pt_element_t *gpt;
 521
 522         if (sp->role.metaphysical || PTTYPE == 32) {
 523                 nonpaging_prefetch_page(vcpu, sp);
 524                 return;
 525         }
 526
 527         gpt = kmap_atomic(gfn_to_page(vcpu->kvm, sp->gfn), KM_USER0);
 528         for (i = 0; i < PT64_ENT_PER_PAGE; ++i)
 529                 if (is_present_pte(gpt[i]))
 530                         sp->spt[i] = shadow_trap_nonpresent_pte;
 531                 else
 532                         sp->spt[i] = shadow_notrap_nonpresent_pte;
 533         kunmap_atomic(gpt, KM_USER0);
 534 }
 535
 536 #undef pt_element_t
 537 #undef guest_walker
 538 #undef FNAME
 539 #undef PT_BASE_ADDR_MASK
 540 #undef PT_INDEX
 541 #undef SHADOW_PT_INDEX
 542 #undef PT_LEVEL_MASK
 543 #undef PT_DIR_BASE_ADDR_MASK
 544 #undef PT_LEVEL_BITS
 545 #undef PT_MAX_FULL_LEVELS