drivers/kvm/paging_tmpl.h

   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_PTE_COPY_MASK PT64_PTE_COPY_MASK
  35 #elif PTTYPE == 32
  36         #define pt_element_t u32
  37         #define guest_walker guest_walker32
  38         #define FNAME(name) paging##32_##name
  39         #define PT_BASE_ADDR_MASK PT32_BASE_ADDR_MASK
  40         #define PT_DIR_BASE_ADDR_MASK PT32_DIR_BASE_ADDR_MASK
  41         #define PT_INDEX(addr, level) PT32_INDEX(addr, level)
  42         #define SHADOW_PT_INDEX(addr, level) PT64_INDEX(addr, level)
  43         #define PT_LEVEL_MASK(level) PT32_LEVEL_MASK(level)
  44         #define PT_PTE_COPY_MASK PT32_PTE_COPY_MASK
  45 #else
  46         #error Invalid PTTYPE value
  47 #endif
  48
  49 /*
  50  * The guest_walker structure emulates the behavior of the hardware page
  51  * table walker.
  52  */
  53 struct guest_walker {
  54         int level;
  55         pt_element_t *table;
  56         pt_element_t inherited_ar;
  57 };
  58
  59 static void FNAME(init_walker)(struct guest_walker *walker,
  60                                struct kvm_vcpu *vcpu)
  61 {
  62         hpa_t hpa;
  63         struct kvm_memory_slot *slot;
  64
  65         walker->level = vcpu->mmu.root_level;
  66         slot = gfn_to_memslot(vcpu->kvm,
  67                               (vcpu->cr3 & PT64_BASE_ADDR_MASK) >> PAGE_SHIFT);
  68         hpa = safe_gpa_to_hpa(vcpu, vcpu->cr3 & PT64_BASE_ADDR_MASK);
  69         walker->table = kmap_atomic(pfn_to_page(hpa >> PAGE_SHIFT), KM_USER0);
  70
  71         ASSERT((!is_long_mode(vcpu) && is_pae(vcpu)) ||
  72                (vcpu->cr3 & ~(PAGE_MASK | CR3_FLAGS_MASK)) == 0);
  73
  74         walker->table = (pt_element_t *)( (unsigned long)walker->table |
  75                 (unsigned long)(vcpu->cr3 & ~(PAGE_MASK | CR3_FLAGS_MASK)) );
  76         walker->inherited_ar = PT_USER_MASK | PT_WRITABLE_MASK;
  77 }
  78
  79 static void FNAME(release_walker)(struct guest_walker *walker)
  80 {
  81         kunmap_atomic(walker->table, KM_USER0);
  82 }
  83
  84 static void FNAME(set_pte)(struct kvm_vcpu *vcpu, u64 guest_pte,
  85                            u64 *shadow_pte, u64 access_bits)
  86 {
  87         ASSERT(*shadow_pte == 0);
  88         access_bits &= guest_pte;
  89         *shadow_pte = (guest_pte & PT_PTE_COPY_MASK);
  90         set_pte_common(vcpu, shadow_pte, guest_pte & PT_BASE_ADDR_MASK,
  91                        guest_pte & PT_DIRTY_MASK, access_bits);
  92 }
  93
  94 static void FNAME(set_pde)(struct kvm_vcpu *vcpu, u64 guest_pde,
  95                            u64 *shadow_pte, u64 access_bits,
  96                            int index)
  97 {
  98         gpa_t gaddr;
  99
 100         ASSERT(*shadow_pte == 0);
 101         access_bits &= guest_pde;
 102         gaddr = (guest_pde & PT_DIR_BASE_ADDR_MASK) + PAGE_SIZE * index;
 103         if (PTTYPE == 32 && is_cpuid_PSE36())
 104                 gaddr |= (guest_pde & PT32_DIR_PSE36_MASK) <<
 105                         (32 - PT32_DIR_PSE36_SHIFT);
 106         *shadow_pte = guest_pde & PT_PTE_COPY_MASK;
 107         set_pte_common(vcpu, shadow_pte, gaddr,
 108                        guest_pde & PT_DIRTY_MASK, access_bits);
 109 }
 110
 111 /*
 112  * Fetch a guest pte from a specific level in the paging hierarchy.
 113  */
 114 static pt_element_t *FNAME(fetch_guest)(struct kvm_vcpu *vcpu,
 115                                         struct guest_walker *walker,
 116                                         int level,
 117                                         gva_t addr)
 118 {
 119
 120         ASSERT(level > 0  && level <= walker->level);
 121
 122         for (;;) {
 123                 int index = PT_INDEX(addr, walker->level);
 124                 hpa_t paddr;
 125
 126                 ASSERT(((unsigned long)walker->table & PAGE_MASK) ==
 127                        ((unsigned long)&walker->table[index] & PAGE_MASK));
 128                 if (level == walker->level ||
 129                     !is_present_pte(walker->table[index]) ||
 130                     (walker->level == PT_DIRECTORY_LEVEL &&
 131                      (walker->table[index] & PT_PAGE_SIZE_MASK) &&
 132                      (PTTYPE == 64 || is_pse(vcpu))))
 133                         return &walker->table[index];
 134                 if (walker->level != 3 || is_long_mode(vcpu))
 135                         walker->inherited_ar &= walker->table[index];
 136                 paddr = safe_gpa_to_hpa(vcpu, walker->table[index] & PT_BASE_ADDR_MASK);
 137                 kunmap_atomic(walker->table, KM_USER0);
 138                 walker->table = kmap_atomic(pfn_to_page(paddr >> PAGE_SHIFT),
 139                                             KM_USER0);
 140                 --walker->level;
 141         }
 142 }
 143
 144 /*
 145  * Fetch a shadow pte for a specific level in the paging hierarchy.
 146  */
 147 static u64 *FNAME(fetch)(struct kvm_vcpu *vcpu, gva_t addr,
 148                               struct guest_walker *walker)
 149 {
 150         hpa_t shadow_addr;
 151         int level;
 152         u64 *prev_shadow_ent = NULL;
 153
 154         shadow_addr = vcpu->mmu.root_hpa;
 155         level = vcpu->mmu.shadow_root_level;
 156
 157         for (; ; level--) {
 158                 u32 index = SHADOW_PT_INDEX(addr, level);
 159                 u64 *shadow_ent = ((u64 *)__va(shadow_addr)) + index;
 160                 pt_element_t *guest_ent;
 161                 u64 shadow_pte;
 162
 163                 if (is_present_pte(*shadow_ent) || is_io_pte(*shadow_ent)) {
 164                         if (level == PT_PAGE_TABLE_LEVEL)
 165                                 return shadow_ent;
 166                         shadow_addr = *shadow_ent & PT64_BASE_ADDR_MASK;
 167                         prev_shadow_ent = shadow_ent;
 168                         continue;
 169                 }
 170
 171                 if (PTTYPE == 32 && level > PT32_ROOT_LEVEL) {
 172                         ASSERT(level == PT32E_ROOT_LEVEL);
 173                         guest_ent = FNAME(fetch_guest)(vcpu, walker,
 174                                                        PT32_ROOT_LEVEL, addr);
 175                 } else
 176                         guest_ent = FNAME(fetch_guest)(vcpu, walker,
 177                                                        level, addr);
 178
 179                 if (!is_present_pte(*guest_ent))
 180                         return NULL;
 181
 182                 /* Don't set accessed bit on PAE PDPTRs */
 183                 if (vcpu->mmu.root_level != 3 || walker->level != 3)
 184                         *guest_ent |= PT_ACCESSED_MASK;
 185
 186                 if (level == PT_PAGE_TABLE_LEVEL) {
 187
 188                         if (walker->level == PT_DIRECTORY_LEVEL) {
 189                                 if (prev_shadow_ent)
 190                                         *prev_shadow_ent |= PT_SHADOW_PS_MARK;
 191                                 FNAME(set_pde)(vcpu, *guest_ent, shadow_ent,
 192                                                walker->inherited_ar,
 193                                           PT_INDEX(addr, PT_PAGE_TABLE_LEVEL));
 194                         } else {
 195                                 ASSERT(walker->level == PT_PAGE_TABLE_LEVEL);
 196                                 FNAME(set_pte)(vcpu, *guest_ent, shadow_ent, walker->inherited_ar);
 197                         }
 198                         return shadow_ent;
 199                 }
 200
 201                 shadow_addr = kvm_mmu_alloc_page(vcpu, shadow_ent);
 202                 if (!VALID_PAGE(shadow_addr))
 203                         return ERR_PTR(-ENOMEM);
 204                 shadow_pte = shadow_addr | PT_PRESENT_MASK;
 205                 if (vcpu->mmu.root_level > 3 || level != 3)
 206                         shadow_pte |= PT_ACCESSED_MASK
 207                                 | PT_WRITABLE_MASK | PT_USER_MASK;
 208                 *shadow_ent = shadow_pte;
 209                 prev_shadow_ent = shadow_ent;
 210         }
 211 }
 212
 213 /*
 214  * The guest faulted for write.  We need to
 215  *
 216  * - check write permissions
 217  * - update the guest pte dirty bit
 218  * - update our own dirty page tracking structures
 219  */
 220 static int FNAME(fix_write_pf)(struct kvm_vcpu *vcpu,
 221                                u64 *shadow_ent,
 222                                struct guest_walker *walker,
 223                                gva_t addr,
 224                                int user)
 225 {
 226         pt_element_t *guest_ent;
 227         int writable_shadow;
 228         gfn_t gfn;
 229
 230         if (is_writeble_pte(*shadow_ent))
 231                 return 0;
 232
 233         writable_shadow = *shadow_ent & PT_SHADOW_WRITABLE_MASK;
 234         if (user) {
 235                 /*
 236                  * User mode access.  Fail if it's a kernel page or a read-only
 237                  * page.
 238                  */
 239                 if (!(*shadow_ent & PT_SHADOW_USER_MASK) || !writable_shadow)
 240                         return 0;
 241                 ASSERT(*shadow_ent & PT_USER_MASK);
 242         } else
 243                 /*
 244                  * Kernel mode access.  Fail if it's a read-only page and
 245                  * supervisor write protection is enabled.
 246                  */
 247                 if (!writable_shadow) {
 248                         if (is_write_protection(vcpu))
 249                                 return 0;
 250                         *shadow_ent &= ~PT_USER_MASK;
 251                 }
 252
 253         guest_ent = FNAME(fetch_guest)(vcpu, walker, PT_PAGE_TABLE_LEVEL, addr);
 254
 255         if (!is_present_pte(*guest_ent)) {
 256                 *shadow_ent = 0;
 257                 return 0;
 258         }
 259
 260         gfn = (*guest_ent & PT64_BASE_ADDR_MASK) >> PAGE_SHIFT;
 261         mark_page_dirty(vcpu->kvm, gfn);
 262         *shadow_ent |= PT_WRITABLE_MASK;
 263         *guest_ent |= PT_DIRTY_MASK;
 264         rmap_add(vcpu->kvm, shadow_ent);
 265
 266         return 1;
 267 }
 268
 269 /*
 270  * Page fault handler.  There are several causes for a page fault:
 271  *   - there is no shadow pte for the guest pte
 272  *   - write access through a shadow pte marked read only so that we can set
 273  *     the dirty bit
 274  *   - write access to a shadow pte marked read only so we can update the page
 275  *     dirty bitmap, when userspace requests it
 276  *   - mmio access; in this case we will never install a present shadow pte
 277  *   - normal guest page fault due to the guest pte marked not present, not
 278  *     writable, or not executable
 279  *
 280  *  Returns: 1 if we need to emulate the instruction, 0 otherwise
 281  */
 282 static int FNAME(page_fault)(struct kvm_vcpu *vcpu, gva_t addr,
 283                                u32 error_code)
 284 {
 285         int write_fault = error_code & PFERR_WRITE_MASK;
 286         int pte_present = error_code & PFERR_PRESENT_MASK;
 287         int user_fault = error_code & PFERR_USER_MASK;
 288         struct guest_walker walker;
 289         u64 *shadow_pte;
 290         int fixed;
 291
 292         /*
 293          * Look up the shadow pte for the faulting address.
 294          */
 295         for (;;) {
 296                 FNAME(init_walker)(&walker, vcpu);
 297                 shadow_pte = FNAME(fetch)(vcpu, addr, &walker);
 298                 if (IS_ERR(shadow_pte)) {  /* must be -ENOMEM */
 299                         nonpaging_flush(vcpu);
 300                         FNAME(release_walker)(&walker);
 301                         continue;
 302                 }
 303                 break;
 304         }
 305
 306         /*
 307          * The page is not mapped by the guest.  Let the guest handle it.
 308          */
 309         if (!shadow_pte) {
 310                 inject_page_fault(vcpu, addr, error_code);
 311                 FNAME(release_walker)(&walker);
 312                 return 0;
 313         }
 314
 315         /*
 316          * Update the shadow pte.
 317          */
 318         if (write_fault)
 319                 fixed = FNAME(fix_write_pf)(vcpu, shadow_pte, &walker, addr,
 320                                             user_fault);
 321         else
 322                 fixed = fix_read_pf(shadow_pte);
 323
 324         FNAME(release_walker)(&walker);
 325
 326         /*
 327          * mmio: emulate if accessible, otherwise its a guest fault.
 328          */
 329         if (is_io_pte(*shadow_pte)) {
 330                 if (may_access(*shadow_pte, write_fault, user_fault))
 331                         return 1;
 332                 pgprintk("%s: io work, no access\n", __FUNCTION__);
 333                 inject_page_fault(vcpu, addr,
 334                                   error_code | PFERR_PRESENT_MASK);
 335                 return 0;
 336         }
 337
 338         /*
 339          * pte not present, guest page fault.
 340          */
 341         if (pte_present && !fixed) {
 342                 inject_page_fault(vcpu, addr, error_code);
 343                 return 0;
 344         }
 345
 346         ++kvm_stat.pf_fixed;
 347
 348         return 0;
 349 }
 350
 351 static gpa_t FNAME(gva_to_gpa)(struct kvm_vcpu *vcpu, gva_t vaddr)
 352 {
 353         struct guest_walker walker;
 354         pt_element_t guest_pte;
 355         gpa_t gpa;
 356
 357         FNAME(init_walker)(&walker, vcpu);
 358         guest_pte = *FNAME(fetch_guest)(vcpu, &walker, PT_PAGE_TABLE_LEVEL,
 359                                         vaddr);
 360         FNAME(release_walker)(&walker);
 361
 362         if (!is_present_pte(guest_pte))
 363                 return UNMAPPED_GVA;
 364
 365         if (walker.level == PT_DIRECTORY_LEVEL) {
 366                 ASSERT((guest_pte & PT_PAGE_SIZE_MASK));
 367                 ASSERT(PTTYPE == 64 || is_pse(vcpu));
 368
 369                 gpa = (guest_pte & PT_DIR_BASE_ADDR_MASK) | (vaddr &
 370                         (PT_LEVEL_MASK(PT_PAGE_TABLE_LEVEL) | ~PAGE_MASK));
 371
 372                 if (PTTYPE == 32 && is_cpuid_PSE36())
 373                         gpa |= (guest_pte & PT32_DIR_PSE36_MASK) <<
 374                                         (32 - PT32_DIR_PSE36_SHIFT);
 375         } else {
 376                 gpa = (guest_pte & PT_BASE_ADDR_MASK);
 377                 gpa |= (vaddr & ~PAGE_MASK);
 378         }
 379
 380         return gpa;
 381 }
 382
 383 #undef pt_element_t
 384 #undef guest_walker
 385 #undef FNAME
 386 #undef PT_BASE_ADDR_MASK
 387 #undef PT_INDEX
 388 #undef SHADOW_PT_INDEX
 389 #undef PT_LEVEL_MASK
 390 #undef PT_PTE_COPY_MASK
 391 #undef PT_NON_PTE_COPY_MASK
 392 #undef PT_DIR_BASE_ADDR_MASK