arch/x86/kvm/mtrr.c

   1 /*
   2  * vMTRR implementation
   3  *
   4  * Copyright (C) 2006 Qumranet, Inc.
   5  * Copyright 2010 Red Hat, Inc. and/or its affiliates.
   6  * Copyright(C) 2015 Intel Corporation.
   7  *
   8  * Authors:
   9  *   Yaniv Kamay  <yaniv@qumranet.com>
  10  *   Avi Kivity   <avi@qumranet.com>
  11  *   Marcelo Tosatti <mtosatti@redhat.com>
  12  *   Paolo Bonzini <pbonzini@redhat.com>
  13  *   Xiao Guangrong <guangrong.xiao@linux.intel.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 #include <linux/kvm_host.h>
  20 #include <asm/mtrr.h>
  21
  22 #include "cpuid.h"
  23 #include "mmu.h"
  24
  25 #define IA32_MTRR_DEF_TYPE_E            (1ULL << 11)
  26 #define IA32_MTRR_DEF_TYPE_FE           (1ULL << 10)
  27 #define IA32_MTRR_DEF_TYPE_TYPE_MASK    (0xff)
  28
  29 static bool msr_mtrr_valid(unsigned msr)
  30 {
  31         switch (msr) {
  32         case 0x200 ... 0x200 + 2 * KVM_NR_VAR_MTRR - 1:
  33         case MSR_MTRRfix64K_00000:
  34         case MSR_MTRRfix16K_80000:
  35         case MSR_MTRRfix16K_A0000:
  36         case MSR_MTRRfix4K_C0000:
  37         case MSR_MTRRfix4K_C8000:
  38         case MSR_MTRRfix4K_D0000:
  39         case MSR_MTRRfix4K_D8000:
  40         case MSR_MTRRfix4K_E0000:
  41         case MSR_MTRRfix4K_E8000:
  42         case MSR_MTRRfix4K_F0000:
  43         case MSR_MTRRfix4K_F8000:
  44         case MSR_MTRRdefType:
  45         case MSR_IA32_CR_PAT:
  46                 return true;
  47         }
  48         return false;
  49 }
  50
  51 static bool valid_pat_type(unsigned t)
  52 {
  53         return t < 8 && (1 << t) & 0xf3; /* 0, 1, 4, 5, 6, 7 */
  54 }
  55
  56 static bool valid_mtrr_type(unsigned t)
  57 {
  58         return t < 8 && (1 << t) & 0x73; /* 0, 1, 4, 5, 6 */
  59 }
  60
  61 bool kvm_mtrr_valid(struct kvm_vcpu *vcpu, u32 msr, u64 data)
  62 {
  63         int i;
  64         u64 mask;
  65
  66         if (!msr_mtrr_valid(msr))
  67                 return false;
  68
  69         if (msr == MSR_IA32_CR_PAT) {
  70                 for (i = 0; i < 8; i++)
  71                         if (!valid_pat_type((data >> (i * 8)) & 0xff))
  72                                 return false;
  73                 return true;
  74         } else if (msr == MSR_MTRRdefType) {
  75                 if (data & ~0xcff)
  76                         return false;
  77                 return valid_mtrr_type(data & 0xff);
  78         } else if (msr >= MSR_MTRRfix64K_00000 && msr <= MSR_MTRRfix4K_F8000) {
  79                 for (i = 0; i < 8 ; i++)
  80                         if (!valid_mtrr_type((data >> (i * 8)) & 0xff))
  81                                 return false;
  82                 return true;
  83         }
  84
  85         /* variable MTRRs */
  86         WARN_ON(!(msr >= 0x200 && msr < 0x200 + 2 * KVM_NR_VAR_MTRR));
  87
  88         mask = (~0ULL) << cpuid_maxphyaddr(vcpu);
  89         if ((msr & 1) == 0) {
  90                 /* MTRR base */
  91                 if (!valid_mtrr_type(data & 0xff))
  92                         return false;
  93                 mask |= 0xf00;
  94         } else
  95                 /* MTRR mask */
  96                 mask |= 0x7ff;
  97         if (data & mask) {
  98                 kvm_inject_gp(vcpu, 0);
  99                 return false;
 100         }
 101
 102         return true;
 103 }
 104 EXPORT_SYMBOL_GPL(kvm_mtrr_valid);
 105
 106 static bool mtrr_is_enabled(struct kvm_mtrr *mtrr_state)
 107 {
 108         return !!(mtrr_state->deftype & IA32_MTRR_DEF_TYPE_E);
 109 }
 110
 111 static bool fixed_mtrr_is_enabled(struct kvm_mtrr *mtrr_state)
 112 {
 113         return !!(mtrr_state->deftype & IA32_MTRR_DEF_TYPE_FE);
 114 }
 115
 116 static u8 mtrr_default_type(struct kvm_mtrr *mtrr_state)
 117 {
 118         return mtrr_state->deftype & IA32_MTRR_DEF_TYPE_TYPE_MASK;
 119 }
 120
 121 static u8 mtrr_disabled_type(struct kvm_vcpu *vcpu)
 122 {
 123         /*
 124          * Intel SDM 11.11.2.2: all MTRRs are disabled when
 125          * IA32_MTRR_DEF_TYPE.E bit is cleared, and the UC
 126          * memory type is applied to all of physical memory.
 127          *
 128          * However, virtual machines can be run with CPUID such that
 129          * there are no MTRRs.  In that case, the firmware will never
 130          * enable MTRRs and it is obviously undesirable to run the
 131          * guest entirely with UC memory and we use WB.
 132          */
 133         if (guest_cpuid_has_mtrr(vcpu))
 134                 return MTRR_TYPE_UNCACHABLE;
 135         else
 136                 return MTRR_TYPE_WRBACK;
 137 }
 138
 139 /*
 140 * Three terms are used in the following code:
 141 * - segment, it indicates the address segments covered by fixed MTRRs.
 142 * - unit, it corresponds to the MSR entry in the segment.
 143 * - range, a range is covered in one memory cache type.
 144 */
 145 struct fixed_mtrr_segment {
 146         u64 start;
 147         u64 end;
 148
 149         int range_shift;
 150
 151         /* the start position in kvm_mtrr.fixed_ranges[]. */
 152         int range_start;
 153 };
 154
 155 static struct fixed_mtrr_segment fixed_seg_table[] = {
 156         /* MSR_MTRRfix64K_00000, 1 unit. 64K fixed mtrr. */
 157         {
 158                 .start = 0x0,
 159                 .end = 0x80000,
 160                 .range_shift = 16, /* 64K */
 161                 .range_start = 0,
 162         },
 163
 164         /*
 165          * MSR_MTRRfix16K_80000 ... MSR_MTRRfix16K_A0000, 2 units,
 166          * 16K fixed mtrr.
 167          */
 168         {
 169                 .start = 0x80000,
 170                 .end = 0xc0000,
 171                 .range_shift = 14, /* 16K */
 172                 .range_start = 8,
 173         },
 174
 175         /*
 176          * MSR_MTRRfix4K_C0000 ... MSR_MTRRfix4K_F8000, 8 units,
 177          * 4K fixed mtrr.
 178          */
 179         {
 180                 .start = 0xc0000,
 181                 .end = 0x100000,
 182                 .range_shift = 12, /* 12K */
 183                 .range_start = 24,
 184         }
 185 };
 186
 187 /*
 188  * The size of unit is covered in one MSR, one MSR entry contains
 189  * 8 ranges so that unit size is always 8 * 2^range_shift.
 190  */
 191 static u64 fixed_mtrr_seg_unit_size(int seg)
 192 {
 193         return 8 << fixed_seg_table[seg].range_shift;
 194 }
 195
 196 static bool fixed_msr_to_seg_unit(u32 msr, int *seg, int *unit)
 197 {
 198         switch (msr) {
 199         case MSR_MTRRfix64K_00000:
 200                 *seg = 0;
 201                 *unit = 0;
 202                 break;
 203         case MSR_MTRRfix16K_80000 ... MSR_MTRRfix16K_A0000:
 204                 *seg = 1;
 205                 *unit = msr - MSR_MTRRfix16K_80000;
 206                 break;
 207         case MSR_MTRRfix4K_C0000 ... MSR_MTRRfix4K_F8000:
 208                 *seg = 2;
 209                 *unit = msr - MSR_MTRRfix4K_C0000;
 210                 break;
 211         default:
 212                 return false;
 213         }
 214
 215         return true;
 216 }
 217
 218 static void fixed_mtrr_seg_unit_range(int seg, int unit, u64 *start, u64 *end)
 219 {
 220         struct fixed_mtrr_segment *mtrr_seg = &fixed_seg_table[seg];
 221         u64 unit_size = fixed_mtrr_seg_unit_size(seg);
 222
 223         *start = mtrr_seg->start + unit * unit_size;
 224         *end = *start + unit_size;
 225         WARN_ON(*end > mtrr_seg->end);
 226 }
 227
 228 static int fixed_mtrr_seg_unit_range_index(int seg, int unit)
 229 {
 230         struct fixed_mtrr_segment *mtrr_seg = &fixed_seg_table[seg];
 231
 232         WARN_ON(mtrr_seg->start + unit * fixed_mtrr_seg_unit_size(seg)
 233                 > mtrr_seg->end);
 234
 235         /* each unit has 8 ranges. */
 236         return mtrr_seg->range_start + 8 * unit;
 237 }
 238
 239 static int fixed_mtrr_seg_end_range_index(int seg)
 240 {
 241         struct fixed_mtrr_segment *mtrr_seg = &fixed_seg_table[seg];
 242         int n;
 243
 244         n = (mtrr_seg->end - mtrr_seg->start) >> mtrr_seg->range_shift;
 245         return mtrr_seg->range_start + n - 1;
 246 }
 247
 248 static bool fixed_msr_to_range(u32 msr, u64 *start, u64 *end)
 249 {
 250         int seg, unit;
 251
 252         if (!fixed_msr_to_seg_unit(msr, &seg, &unit))
 253                 return false;
 254
 255         fixed_mtrr_seg_unit_range(seg, unit, start, end);
 256         return true;
 257 }
 258
 259 static int fixed_msr_to_range_index(u32 msr)
 260 {
 261         int seg, unit;
 262
 263         if (!fixed_msr_to_seg_unit(msr, &seg, &unit))
 264                 return -1;
 265
 266         return fixed_mtrr_seg_unit_range_index(seg, unit);
 267 }
 268
 269 static int fixed_mtrr_addr_to_seg(u64 addr)
 270 {
 271         struct fixed_mtrr_segment *mtrr_seg;
 272         int seg, seg_num = ARRAY_SIZE(fixed_seg_table);
 273
 274         for (seg = 0; seg < seg_num; seg++) {
 275                 mtrr_seg = &fixed_seg_table[seg];
 276                 if (mtrr_seg->start <= addr && addr < mtrr_seg->end)
 277                         return seg;
 278         }
 279
 280         return -1;
 281 }
 282
 283 static int fixed_mtrr_addr_seg_to_range_index(u64 addr, int seg)
 284 {
 285         struct fixed_mtrr_segment *mtrr_seg;
 286         int index;
 287
 288         mtrr_seg = &fixed_seg_table[seg];
 289         index = mtrr_seg->range_start;
 290         index += (addr - mtrr_seg->start) >> mtrr_seg->range_shift;
 291         return index;
 292 }
 293
 294 static u64 fixed_mtrr_range_end_addr(int seg, int index)
 295 {
 296         struct fixed_mtrr_segment *mtrr_seg = &fixed_seg_table[seg];
 297         int pos = index - mtrr_seg->range_start;
 298
 299         return mtrr_seg->start + ((pos + 1) << mtrr_seg->range_shift);
 300 }
 301
 302 static void var_mtrr_range(struct kvm_mtrr_range *range, u64 *start, u64 *end)
 303 {
 304         u64 mask;
 305
 306         *start = range->base & PAGE_MASK;
 307
 308         mask = range->mask & PAGE_MASK;
 309
 310         /* This cannot overflow because writing to the reserved bits of
 311          * variable MTRRs causes a #GP.
 312          */
 313         *end = (*start | ~mask) + 1;
 314 }
 315
 316 static void update_mtrr(struct kvm_vcpu *vcpu, u32 msr)
 317 {
 318         struct kvm_mtrr *mtrr_state = &vcpu->arch.mtrr_state;
 319         gfn_t start, end;
 320         int index;
 321
 322         if (msr == MSR_IA32_CR_PAT || !tdp_enabled ||
 323               !kvm_arch_has_noncoherent_dma(vcpu->kvm))
 324                 return;
 325
 326         if (!mtrr_is_enabled(mtrr_state) && msr != MSR_MTRRdefType)
 327                 return;
 328
 329         /* fixed MTRRs. */
 330         if (fixed_msr_to_range(msr, &start, &end)) {
 331                 if (!fixed_mtrr_is_enabled(mtrr_state))
 332                         return;
 333         } else if (msr == MSR_MTRRdefType) {
 334                 start = 0x0;
 335                 end = ~0ULL;
 336         } else {
 337                 /* variable range MTRRs. */
 338                 index = (msr - 0x200) / 2;
 339                 var_mtrr_range(&mtrr_state->var_ranges[index], &start, &end);
 340         }
 341
 342         kvm_zap_gfn_range(vcpu->kvm, gpa_to_gfn(start), gpa_to_gfn(end));
 343 }
 344
 345 static bool var_mtrr_range_is_valid(struct kvm_mtrr_range *range)
 346 {
 347         return (range->mask & (1 << 11)) != 0;
 348 }
 349
 350 static void set_var_mtrr_msr(struct kvm_vcpu *vcpu, u32 msr, u64 data)
 351 {
 352         struct kvm_mtrr *mtrr_state = &vcpu->arch.mtrr_state;
 353         struct kvm_mtrr_range *tmp, *cur;
 354         int index, is_mtrr_mask;
 355
 356         index = (msr - 0x200) / 2;
 357         is_mtrr_mask = msr - 0x200 - 2 * index;
 358         cur = &mtrr_state->var_ranges[index];
 359
 360         /* remove the entry if it's in the list. */
 361         if (var_mtrr_range_is_valid(cur))
 362                 list_del(&mtrr_state->var_ranges[index].node);
 363
 364         /* Extend the mask with all 1 bits to the left, since those
 365          * bits must implicitly be 0.  The bits are then cleared
 366          * when reading them.
 367          */
 368         if (!is_mtrr_mask)
 369                 cur->base = data;
 370         else
 371                 cur->mask = data | (-1LL << cpuid_maxphyaddr(vcpu));
 372
 373         /* add it to the list if it's enabled. */
 374         if (var_mtrr_range_is_valid(cur)) {
 375                 list_for_each_entry(tmp, &mtrr_state->head, node)
 376                         if (cur->base >= tmp->base)
 377                                 break;
 378                 list_add_tail(&cur->node, &tmp->node);
 379         }
 380 }
 381
 382 int kvm_mtrr_set_msr(struct kvm_vcpu *vcpu, u32 msr, u64 data)
 383 {
 384         int index;
 385
 386         if (!kvm_mtrr_valid(vcpu, msr, data))
 387                 return 1;
 388
 389         index = fixed_msr_to_range_index(msr);
 390         if (index >= 0)
 391                 *(u64 *)&vcpu->arch.mtrr_state.fixed_ranges[index] = data;
 392         else if (msr == MSR_MTRRdefType)
 393                 vcpu->arch.mtrr_state.deftype = data;
 394         else if (msr == MSR_IA32_CR_PAT)
 395                 vcpu->arch.pat = data;
 396         else
 397                 set_var_mtrr_msr(vcpu, msr, data);
 398
 399         update_mtrr(vcpu, msr);
 400         return 0;
 401 }
 402
 403 int kvm_mtrr_get_msr(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata)
 404 {
 405         int index;
 406
 407         /* MSR_MTRRcap is a readonly MSR. */
 408         if (msr == MSR_MTRRcap) {
 409                 /*
 410                  * SMRR = 0
 411                  * WC = 1
 412                  * FIX = 1
 413                  * VCNT = KVM_NR_VAR_MTRR
 414                  */
 415                 *pdata = 0x500 | KVM_NR_VAR_MTRR;
 416                 return 0;
 417         }
 418
 419         if (!msr_mtrr_valid(msr))
 420                 return 1;
 421
 422         index = fixed_msr_to_range_index(msr);
 423         if (index >= 0)
 424                 *pdata = *(u64 *)&vcpu->arch.mtrr_state.fixed_ranges[index];
 425         else if (msr == MSR_MTRRdefType)
 426                 *pdata = vcpu->arch.mtrr_state.deftype;
 427         else if (msr == MSR_IA32_CR_PAT)
 428                 *pdata = vcpu->arch.pat;
 429         else {  /* Variable MTRRs */
 430                 int is_mtrr_mask;
 431
 432                 index = (msr - 0x200) / 2;
 433                 is_mtrr_mask = msr - 0x200 - 2 * index;
 434                 if (!is_mtrr_mask)
 435                         *pdata = vcpu->arch.mtrr_state.var_ranges[index].base;
 436                 else
 437                         *pdata = vcpu->arch.mtrr_state.var_ranges[index].mask;
 438
 439                 *pdata &= (1ULL << cpuid_maxphyaddr(vcpu)) - 1;
 440         }
 441
 442         return 0;
 443 }
 444
 445 void kvm_vcpu_mtrr_init(struct kvm_vcpu *vcpu)
 446 {
 447         INIT_LIST_HEAD(&vcpu->arch.mtrr_state.head);
 448 }
 449
 450 struct mtrr_iter {
 451         /* input fields. */
 452         struct kvm_mtrr *mtrr_state;
 453         u64 start;
 454         u64 end;
 455
 456         /* output fields. */
 457         int mem_type;
 458         /* mtrr is completely disabled? */
 459         bool mtrr_disabled;
 460         /* [start, end) is not fully covered in MTRRs? */
 461         bool partial_map;
 462
 463         /* private fields. */
 464         union {
 465                 /* used for fixed MTRRs. */
 466                 struct {
 467                         int index;
 468                         int seg;
 469                 };
 470
 471                 /* used for var MTRRs. */
 472                 struct {
 473                         struct kvm_mtrr_range *range;
 474                         /* max address has been covered in var MTRRs. */
 475                         u64 start_max;
 476                 };
 477         };
 478
 479         bool fixed;
 480 };
 481
 482 static bool mtrr_lookup_fixed_start(struct mtrr_iter *iter)
 483 {
 484         int seg, index;
 485
 486         if (!fixed_mtrr_is_enabled(iter->mtrr_state))
 487                 return false;
 488
 489         seg = fixed_mtrr_addr_to_seg(iter->start);
 490         if (seg < 0)
 491                 return false;
 492
 493         iter->fixed = true;
 494         index = fixed_mtrr_addr_seg_to_range_index(iter->start, seg);
 495         iter->index = index;
 496         iter->seg = seg;
 497         return true;
 498 }
 499
 500 static bool match_var_range(struct mtrr_iter *iter,
 501                             struct kvm_mtrr_range *range)
 502 {
 503         u64 start, end;
 504
 505         var_mtrr_range(range, &start, &end);
 506         if (!(start >= iter->end || end <= iter->start)) {
 507                 iter->range = range;
 508
 509                 /*
 510                  * the function is called when we do kvm_mtrr.head walking.
 511                  * Range has the minimum base address which interleaves
 512                  * [looker->start_max, looker->end).
 513                  */
 514                 iter->partial_map |= iter->start_max < start;
 515
 516                 /* update the max address has been covered. */
 517                 iter->start_max = max(iter->start_max, end);
 518                 return true;
 519         }
 520
 521         return false;
 522 }
 523
 524 static void __mtrr_lookup_var_next(struct mtrr_iter *iter)
 525 {
 526         struct kvm_mtrr *mtrr_state = iter->mtrr_state;
 527
 528         list_for_each_entry_continue(iter->range, &mtrr_state->head, node)
 529                 if (match_var_range(iter, iter->range))
 530                         return;
 531
 532         iter->range = NULL;
 533         iter->partial_map |= iter->start_max < iter->end;
 534 }
 535
 536 static void mtrr_lookup_var_start(struct mtrr_iter *iter)
 537 {
 538         struct kvm_mtrr *mtrr_state = iter->mtrr_state;
 539
 540         iter->fixed = false;
 541         iter->start_max = iter->start;
 542         iter->range = NULL;
 543         iter->range = list_prepare_entry(iter->range, &mtrr_state->head, node);
 544
 545         __mtrr_lookup_var_next(iter);
 546 }
 547
 548 static void mtrr_lookup_fixed_next(struct mtrr_iter *iter)
 549 {
 550         /* terminate the lookup. */
 551         if (fixed_mtrr_range_end_addr(iter->seg, iter->index) >= iter->end) {
 552                 iter->fixed = false;
 553                 iter->range = NULL;
 554                 return;
 555         }
 556
 557         iter->index++;
 558
 559         /* have looked up for all fixed MTRRs. */
 560         if (iter->index >= ARRAY_SIZE(iter->mtrr_state->fixed_ranges))
 561                 return mtrr_lookup_var_start(iter);
 562
 563         /* switch to next segment. */
 564         if (iter->index > fixed_mtrr_seg_end_range_index(iter->seg))
 565                 iter->seg++;
 566 }
 567
 568 static void mtrr_lookup_var_next(struct mtrr_iter *iter)
 569 {
 570         __mtrr_lookup_var_next(iter);
 571 }
 572
 573 static void mtrr_lookup_start(struct mtrr_iter *iter)
 574 {
 575         if (!mtrr_is_enabled(iter->mtrr_state)) {
 576                 iter->mtrr_disabled = true;
 577                 return;
 578         }
 579
 580         if (!mtrr_lookup_fixed_start(iter))
 581                 mtrr_lookup_var_start(iter);
 582 }
 583
 584 static void mtrr_lookup_init(struct mtrr_iter *iter,
 585                              struct kvm_mtrr *mtrr_state, u64 start, u64 end)
 586 {
 587         iter->mtrr_state = mtrr_state;
 588         iter->start = start;
 589         iter->end = end;
 590         iter->mtrr_disabled = false;
 591         iter->partial_map = false;
 592         iter->fixed = false;
 593         iter->range = NULL;
 594
 595         mtrr_lookup_start(iter);
 596 }
 597
 598 static bool mtrr_lookup_okay(struct mtrr_iter *iter)
 599 {
 600         if (iter->fixed) {
 601                 iter->mem_type = iter->mtrr_state->fixed_ranges[iter->index];
 602                 return true;
 603         }
 604
 605         if (iter->range) {
 606                 iter->mem_type = iter->range->base & 0xff;
 607                 return true;
 608         }
 609
 610         return false;
 611 }
 612
 613 static void mtrr_lookup_next(struct mtrr_iter *iter)
 614 {
 615         if (iter->fixed)
 616                 mtrr_lookup_fixed_next(iter);
 617         else
 618                 mtrr_lookup_var_next(iter);
 619 }
 620
 621 #define mtrr_for_each_mem_type(_iter_, _mtrr_, _gpa_start_, _gpa_end_) \
 622         for (mtrr_lookup_init(_iter_, _mtrr_, _gpa_start_, _gpa_end_); \
 623              mtrr_lookup_okay(_iter_); mtrr_lookup_next(_iter_))
 624
 625 u8 kvm_mtrr_get_guest_memory_type(struct kvm_vcpu *vcpu, gfn_t gfn)
 626 {
 627         struct kvm_mtrr *mtrr_state = &vcpu->arch.mtrr_state;
 628         struct mtrr_iter iter;
 629         u64 start, end;
 630         int type = -1;
 631         const int wt_wb_mask = (1 << MTRR_TYPE_WRBACK)
 632                                | (1 << MTRR_TYPE_WRTHROUGH);
 633
 634         start = gfn_to_gpa(gfn);
 635         end = start + PAGE_SIZE;
 636
 637         mtrr_for_each_mem_type(&iter, mtrr_state, start, end) {
 638                 int curr_type = iter.mem_type;
 639
 640                 /*
 641                  * Please refer to Intel SDM Volume 3: 11.11.4.1 MTRR
 642                  * Precedences.
 643                  */
 644
 645                 if (type == -1) {
 646                         type = curr_type;
 647                         continue;
 648                 }
 649
 650                 /*
 651                  * If two or more variable memory ranges match and the
 652                  * memory types are identical, then that memory type is
 653                  * used.
 654                  */
 655                 if (type == curr_type)
 656                         continue;
 657
 658                 /*
 659                  * If two or more variable memory ranges match and one of
 660                  * the memory types is UC, the UC memory type used.
 661                  */
 662                 if (curr_type == MTRR_TYPE_UNCACHABLE)
 663                         return MTRR_TYPE_UNCACHABLE;
 664
 665                 /*
 666                  * If two or more variable memory ranges match and the
 667                  * memory types are WT and WB, the WT memory type is used.
 668                  */
 669                 if (((1 << type) & wt_wb_mask) &&
 670                       ((1 << curr_type) & wt_wb_mask)) {
 671                         type = MTRR_TYPE_WRTHROUGH;
 672                         continue;
 673                 }
 674
 675                 /*
 676                  * For overlaps not defined by the above rules, processor
 677                  * behavior is undefined.
 678                  */
 679
 680                 /* We use WB for this undefined behavior. :( */
 681                 return MTRR_TYPE_WRBACK;
 682         }
 683
 684         if (iter.mtrr_disabled)
 685                 return mtrr_disabled_type(vcpu);
 686
 687         /* not contained in any MTRRs. */
 688         if (type == -1)
 689                 return mtrr_default_type(mtrr_state);
 690
 691         /*
 692          * We just check one page, partially covered by MTRRs is
 693          * impossible.
 694          */
 695         WARN_ON(iter.partial_map);
 696
 697         return type;
 698 }
 699 EXPORT_SYMBOL_GPL(kvm_mtrr_get_guest_memory_type);
 700
 701 bool kvm_mtrr_check_gfn_range_consistency(struct kvm_vcpu *vcpu, gfn_t gfn,
 702                                           int page_num)
 703 {
 704         struct kvm_mtrr *mtrr_state = &vcpu->arch.mtrr_state;
 705         struct mtrr_iter iter;
 706         u64 start, end;
 707         int type = -1;
 708
 709         start = gfn_to_gpa(gfn);
 710         end = gfn_to_gpa(gfn + page_num);
 711         mtrr_for_each_mem_type(&iter, mtrr_state, start, end) {
 712                 if (type == -1) {
 713                         type = iter.mem_type;
 714                         continue;
 715                 }
 716
 717                 if (type != iter.mem_type)
 718                         return false;
 719         }
 720
 721         if (iter.mtrr_disabled)
 722                 return true;
 723
 724         if (!iter.partial_map)
 725                 return true;
 726
 727         if (type == -1)
 728                 return true;
 729
 730         return type == mtrr_default_type(mtrr_state);
 731 }