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(vcpu, X86_FEATURE_MTRR))
 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 = array_index_nospec(
 206                         msr - MSR_MTRRfix16K_80000,
 207                         MSR_MTRRfix16K_A0000 - MSR_MTRRfix16K_80000 + 1);
 208                 break;
 209         case MSR_MTRRfix4K_C0000 ... MSR_MTRRfix4K_F8000:
 210                 *seg = 2;
 211                 *unit = array_index_nospec(
 212                         msr - MSR_MTRRfix4K_C0000,
 213                         MSR_MTRRfix4K_F8000 - MSR_MTRRfix4K_C0000 + 1);
 214                 break;
 215         default:
 216                 return false;
 217         }
 218
 219         return true;
 220 }
 221
 222 static void fixed_mtrr_seg_unit_range(int seg, int unit, u64 *start, u64 *end)
 223 {
 224         struct fixed_mtrr_segment *mtrr_seg = &fixed_seg_table[seg];
 225         u64 unit_size = fixed_mtrr_seg_unit_size(seg);
 226
 227         *start = mtrr_seg->start + unit * unit_size;
 228         *end = *start + unit_size;
 229         WARN_ON(*end > mtrr_seg->end);
 230 }
 231
 232 static int fixed_mtrr_seg_unit_range_index(int seg, int unit)
 233 {
 234         struct fixed_mtrr_segment *mtrr_seg = &fixed_seg_table[seg];
 235
 236         WARN_ON(mtrr_seg->start + unit * fixed_mtrr_seg_unit_size(seg)
 237                 > mtrr_seg->end);
 238
 239         /* each unit has 8 ranges. */
 240         return mtrr_seg->range_start + 8 * unit;
 241 }
 242
 243 static int fixed_mtrr_seg_end_range_index(int seg)
 244 {
 245         struct fixed_mtrr_segment *mtrr_seg = &fixed_seg_table[seg];
 246         int n;
 247
 248         n = (mtrr_seg->end - mtrr_seg->start) >> mtrr_seg->range_shift;
 249         return mtrr_seg->range_start + n - 1;
 250 }
 251
 252 static bool fixed_msr_to_range(u32 msr, u64 *start, u64 *end)
 253 {
 254         int seg, unit;
 255
 256         if (!fixed_msr_to_seg_unit(msr, &seg, &unit))
 257                 return false;
 258
 259         fixed_mtrr_seg_unit_range(seg, unit, start, end);
 260         return true;
 261 }
 262
 263 static int fixed_msr_to_range_index(u32 msr)
 264 {
 265         int seg, unit;
 266
 267         if (!fixed_msr_to_seg_unit(msr, &seg, &unit))
 268                 return -1;
 269
 270         return fixed_mtrr_seg_unit_range_index(seg, unit);
 271 }
 272
 273 static int fixed_mtrr_addr_to_seg(u64 addr)
 274 {
 275         struct fixed_mtrr_segment *mtrr_seg;
 276         int seg, seg_num = ARRAY_SIZE(fixed_seg_table);
 277
 278         for (seg = 0; seg < seg_num; seg++) {
 279                 mtrr_seg = &fixed_seg_table[seg];
 280                 if (mtrr_seg->start <= addr && addr < mtrr_seg->end)
 281                         return seg;
 282         }
 283
 284         return -1;
 285 }
 286
 287 static int fixed_mtrr_addr_seg_to_range_index(u64 addr, int seg)
 288 {
 289         struct fixed_mtrr_segment *mtrr_seg;
 290         int index;
 291
 292         mtrr_seg = &fixed_seg_table[seg];
 293         index = mtrr_seg->range_start;
 294         index += (addr - mtrr_seg->start) >> mtrr_seg->range_shift;
 295         return index;
 296 }
 297
 298 static u64 fixed_mtrr_range_end_addr(int seg, int index)
 299 {
 300         struct fixed_mtrr_segment *mtrr_seg = &fixed_seg_table[seg];
 301         int pos = index - mtrr_seg->range_start;
 302
 303         return mtrr_seg->start + ((pos + 1) << mtrr_seg->range_shift);
 304 }
 305
 306 static void var_mtrr_range(struct kvm_mtrr_range *range, u64 *start, u64 *end)
 307 {
 308         u64 mask;
 309
 310         *start = range->base & PAGE_MASK;
 311
 312         mask = range->mask & PAGE_MASK;
 313
 314         /* This cannot overflow because writing to the reserved bits of
 315          * variable MTRRs causes a #GP.
 316          */
 317         *end = (*start | ~mask) + 1;
 318 }
 319
 320 static void update_mtrr(struct kvm_vcpu *vcpu, u32 msr)
 321 {
 322         struct kvm_mtrr *mtrr_state = &vcpu->arch.mtrr_state;
 323         gfn_t start, end;
 324         int index;
 325
 326         if (msr == MSR_IA32_CR_PAT || !tdp_enabled ||
 327               !kvm_arch_has_noncoherent_dma(vcpu->kvm))
 328                 return;
 329
 330         if (!mtrr_is_enabled(mtrr_state) && msr != MSR_MTRRdefType)
 331                 return;
 332
 333         /* fixed MTRRs. */
 334         if (fixed_msr_to_range(msr, &start, &end)) {
 335                 if (!fixed_mtrr_is_enabled(mtrr_state))
 336                         return;
 337         } else if (msr == MSR_MTRRdefType) {
 338                 start = 0x0;
 339                 end = ~0ULL;
 340         } else {
 341                 /* variable range MTRRs. */
 342                 index = (msr - 0x200) / 2;
 343                 var_mtrr_range(&mtrr_state->var_ranges[index], &start, &end);
 344         }
 345
 346         kvm_zap_gfn_range(vcpu->kvm, gpa_to_gfn(start), gpa_to_gfn(end));
 347 }
 348
 349 static bool var_mtrr_range_is_valid(struct kvm_mtrr_range *range)
 350 {
 351         return (range->mask & (1 << 11)) != 0;
 352 }
 353
 354 static void set_var_mtrr_msr(struct kvm_vcpu *vcpu, u32 msr, u64 data)
 355 {
 356         struct kvm_mtrr *mtrr_state = &vcpu->arch.mtrr_state;
 357         struct kvm_mtrr_range *tmp, *cur;
 358         int index, is_mtrr_mask;
 359
 360         index = (msr - 0x200) / 2;
 361         is_mtrr_mask = msr - 0x200 - 2 * index;
 362         cur = &mtrr_state->var_ranges[index];
 363
 364         /* remove the entry if it's in the list. */
 365         if (var_mtrr_range_is_valid(cur))
 366                 list_del(&mtrr_state->var_ranges[index].node);
 367
 368         /* Extend the mask with all 1 bits to the left, since those
 369          * bits must implicitly be 0.  The bits are then cleared
 370          * when reading them.
 371          */
 372         if (!is_mtrr_mask)
 373                 cur->base = data;
 374         else
 375                 cur->mask = data | (-1LL << cpuid_maxphyaddr(vcpu));
 376
 377         /* add it to the list if it's enabled. */
 378         if (var_mtrr_range_is_valid(cur)) {
 379                 list_for_each_entry(tmp, &mtrr_state->head, node)
 380                         if (cur->base >= tmp->base)
 381                                 break;
 382                 list_add_tail(&cur->node, &tmp->node);
 383         }
 384 }
 385
 386 int kvm_mtrr_set_msr(struct kvm_vcpu *vcpu, u32 msr, u64 data)
 387 {
 388         int index;
 389
 390         if (!kvm_mtrr_valid(vcpu, msr, data))
 391                 return 1;
 392
 393         index = fixed_msr_to_range_index(msr);
 394         if (index >= 0)
 395                 *(u64 *)&vcpu->arch.mtrr_state.fixed_ranges[index] = data;
 396         else if (msr == MSR_MTRRdefType)
 397                 vcpu->arch.mtrr_state.deftype = data;
 398         else if (msr == MSR_IA32_CR_PAT)
 399                 vcpu->arch.pat = data;
 400         else
 401                 set_var_mtrr_msr(vcpu, msr, data);
 402
 403         update_mtrr(vcpu, msr);
 404         return 0;
 405 }
 406
 407 int kvm_mtrr_get_msr(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata)
 408 {
 409         int index;
 410
 411         /* MSR_MTRRcap is a readonly MSR. */
 412         if (msr == MSR_MTRRcap) {
 413                 /*
 414                  * SMRR = 0
 415                  * WC = 1
 416                  * FIX = 1
 417                  * VCNT = KVM_NR_VAR_MTRR
 418                  */
 419                 *pdata = 0x500 | KVM_NR_VAR_MTRR;
 420                 return 0;
 421         }
 422
 423         if (!msr_mtrr_valid(msr))
 424                 return 1;
 425
 426         index = fixed_msr_to_range_index(msr);
 427         if (index >= 0)
 428                 *pdata = *(u64 *)&vcpu->arch.mtrr_state.fixed_ranges[index];
 429         else if (msr == MSR_MTRRdefType)
 430                 *pdata = vcpu->arch.mtrr_state.deftype;
 431         else if (msr == MSR_IA32_CR_PAT)
 432                 *pdata = vcpu->arch.pat;
 433         else {  /* Variable MTRRs */
 434                 int is_mtrr_mask;
 435
 436                 index = (msr - 0x200) / 2;
 437                 is_mtrr_mask = msr - 0x200 - 2 * index;
 438                 if (!is_mtrr_mask)
 439                         *pdata = vcpu->arch.mtrr_state.var_ranges[index].base;
 440                 else
 441                         *pdata = vcpu->arch.mtrr_state.var_ranges[index].mask;
 442
 443                 *pdata &= (1ULL << cpuid_maxphyaddr(vcpu)) - 1;
 444         }
 445
 446         return 0;
 447 }
 448
 449 void kvm_vcpu_mtrr_init(struct kvm_vcpu *vcpu)
 450 {
 451         INIT_LIST_HEAD(&vcpu->arch.mtrr_state.head);
 452 }
 453
 454 struct mtrr_iter {
 455         /* input fields. */
 456         struct kvm_mtrr *mtrr_state;
 457         u64 start;
 458         u64 end;
 459
 460         /* output fields. */
 461         int mem_type;
 462         /* mtrr is completely disabled? */
 463         bool mtrr_disabled;
 464         /* [start, end) is not fully covered in MTRRs? */
 465         bool partial_map;
 466
 467         /* private fields. */
 468         union {
 469                 /* used for fixed MTRRs. */
 470                 struct {
 471                         int index;
 472                         int seg;
 473                 };
 474
 475                 /* used for var MTRRs. */
 476                 struct {
 477                         struct kvm_mtrr_range *range;
 478                         /* max address has been covered in var MTRRs. */
 479                         u64 start_max;
 480                 };
 481         };
 482
 483         bool fixed;
 484 };
 485
 486 static bool mtrr_lookup_fixed_start(struct mtrr_iter *iter)
 487 {
 488         int seg, index;
 489
 490         if (!fixed_mtrr_is_enabled(iter->mtrr_state))
 491                 return false;
 492
 493         seg = fixed_mtrr_addr_to_seg(iter->start);
 494         if (seg < 0)
 495                 return false;
 496
 497         iter->fixed = true;
 498         index = fixed_mtrr_addr_seg_to_range_index(iter->start, seg);
 499         iter->index = index;
 500         iter->seg = seg;
 501         return true;
 502 }
 503
 504 static bool match_var_range(struct mtrr_iter *iter,
 505                             struct kvm_mtrr_range *range)
 506 {
 507         u64 start, end;
 508
 509         var_mtrr_range(range, &start, &end);
 510         if (!(start >= iter->end || end <= iter->start)) {
 511                 iter->range = range;
 512
 513                 /*
 514                  * the function is called when we do kvm_mtrr.head walking.
 515                  * Range has the minimum base address which interleaves
 516                  * [looker->start_max, looker->end).
 517                  */
 518                 iter->partial_map |= iter->start_max < start;
 519
 520                 /* update the max address has been covered. */
 521                 iter->start_max = max(iter->start_max, end);
 522                 return true;
 523         }
 524
 525         return false;
 526 }
 527
 528 static void __mtrr_lookup_var_next(struct mtrr_iter *iter)
 529 {
 530         struct kvm_mtrr *mtrr_state = iter->mtrr_state;
 531
 532         list_for_each_entry_continue(iter->range, &mtrr_state->head, node)
 533                 if (match_var_range(iter, iter->range))
 534                         return;
 535
 536         iter->range = NULL;
 537         iter->partial_map |= iter->start_max < iter->end;
 538 }
 539
 540 static void mtrr_lookup_var_start(struct mtrr_iter *iter)
 541 {
 542         struct kvm_mtrr *mtrr_state = iter->mtrr_state;
 543
 544         iter->fixed = false;
 545         iter->start_max = iter->start;
 546         iter->range = NULL;
 547         iter->range = list_prepare_entry(iter->range, &mtrr_state->head, node);
 548
 549         __mtrr_lookup_var_next(iter);
 550 }
 551
 552 static void mtrr_lookup_fixed_next(struct mtrr_iter *iter)
 553 {
 554         /* terminate the lookup. */
 555         if (fixed_mtrr_range_end_addr(iter->seg, iter->index) >= iter->end) {
 556                 iter->fixed = false;
 557                 iter->range = NULL;
 558                 return;
 559         }
 560
 561         iter->index++;
 562
 563         /* have looked up for all fixed MTRRs. */
 564         if (iter->index >= ARRAY_SIZE(iter->mtrr_state->fixed_ranges))
 565                 return mtrr_lookup_var_start(iter);
 566
 567         /* switch to next segment. */
 568         if (iter->index > fixed_mtrr_seg_end_range_index(iter->seg))
 569                 iter->seg++;
 570 }
 571
 572 static void mtrr_lookup_var_next(struct mtrr_iter *iter)
 573 {
 574         __mtrr_lookup_var_next(iter);
 575 }
 576
 577 static void mtrr_lookup_start(struct mtrr_iter *iter)
 578 {
 579         if (!mtrr_is_enabled(iter->mtrr_state)) {
 580                 iter->mtrr_disabled = true;
 581                 return;
 582         }
 583
 584         if (!mtrr_lookup_fixed_start(iter))
 585                 mtrr_lookup_var_start(iter);
 586 }
 587
 588 static void mtrr_lookup_init(struct mtrr_iter *iter,
 589                              struct kvm_mtrr *mtrr_state, u64 start, u64 end)
 590 {
 591         iter->mtrr_state = mtrr_state;
 592         iter->start = start;
 593         iter->end = end;
 594         iter->mtrr_disabled = false;
 595         iter->partial_map = false;
 596         iter->fixed = false;
 597         iter->range = NULL;
 598
 599         mtrr_lookup_start(iter);
 600 }
 601
 602 static bool mtrr_lookup_okay(struct mtrr_iter *iter)
 603 {
 604         if (iter->fixed) {
 605                 iter->mem_type = iter->mtrr_state->fixed_ranges[iter->index];
 606                 return true;
 607         }
 608
 609         if (iter->range) {
 610                 iter->mem_type = iter->range->base & 0xff;
 611                 return true;
 612         }
 613
 614         return false;
 615 }
 616
 617 static void mtrr_lookup_next(struct mtrr_iter *iter)
 618 {
 619         if (iter->fixed)
 620                 mtrr_lookup_fixed_next(iter);
 621         else
 622                 mtrr_lookup_var_next(iter);
 623 }
 624
 625 #define mtrr_for_each_mem_type(_iter_, _mtrr_, _gpa_start_, _gpa_end_) \
 626         for (mtrr_lookup_init(_iter_, _mtrr_, _gpa_start_, _gpa_end_); \
 627              mtrr_lookup_okay(_iter_); mtrr_lookup_next(_iter_))
 628
 629 u8 kvm_mtrr_get_guest_memory_type(struct kvm_vcpu *vcpu, gfn_t gfn)
 630 {
 631         struct kvm_mtrr *mtrr_state = &vcpu->arch.mtrr_state;
 632         struct mtrr_iter iter;
 633         u64 start, end;
 634         int type = -1;
 635         const int wt_wb_mask = (1 << MTRR_TYPE_WRBACK)
 636                                | (1 << MTRR_TYPE_WRTHROUGH);
 637
 638         start = gfn_to_gpa(gfn);
 639         end = start + PAGE_SIZE;
 640
 641         mtrr_for_each_mem_type(&iter, mtrr_state, start, end) {
 642                 int curr_type = iter.mem_type;
 643
 644                 /*
 645                  * Please refer to Intel SDM Volume 3: 11.11.4.1 MTRR
 646                  * Precedences.
 647                  */
 648
 649                 if (type == -1) {
 650                         type = curr_type;
 651                         continue;
 652                 }
 653
 654                 /*
 655                  * If two or more variable memory ranges match and the
 656                  * memory types are identical, then that memory type is
 657                  * used.
 658                  */
 659                 if (type == curr_type)
 660                         continue;
 661
 662                 /*
 663                  * If two or more variable memory ranges match and one of
 664                  * the memory types is UC, the UC memory type used.
 665                  */
 666                 if (curr_type == MTRR_TYPE_UNCACHABLE)
 667                         return MTRR_TYPE_UNCACHABLE;
 668
 669                 /*
 670                  * If two or more variable memory ranges match and the
 671                  * memory types are WT and WB, the WT memory type is used.
 672                  */
 673                 if (((1 << type) & wt_wb_mask) &&
 674                       ((1 << curr_type) & wt_wb_mask)) {
 675                         type = MTRR_TYPE_WRTHROUGH;
 676                         continue;
 677                 }
 678
 679                 /*
 680                  * For overlaps not defined by the above rules, processor
 681                  * behavior is undefined.
 682                  */
 683
 684                 /* We use WB for this undefined behavior. :( */
 685                 return MTRR_TYPE_WRBACK;
 686         }
 687
 688         if (iter.mtrr_disabled)
 689                 return mtrr_disabled_type(vcpu);
 690
 691         /* not contained in any MTRRs. */
 692         if (type == -1)
 693                 return mtrr_default_type(mtrr_state);
 694
 695         /*
 696          * We just check one page, partially covered by MTRRs is
 697          * impossible.
 698          */
 699         WARN_ON(iter.partial_map);
 700
 701         return type;
 702 }
 703 EXPORT_SYMBOL_GPL(kvm_mtrr_get_guest_memory_type);
 704
 705 bool kvm_mtrr_check_gfn_range_consistency(struct kvm_vcpu *vcpu, gfn_t gfn,
 706                                           int page_num)
 707 {
 708         struct kvm_mtrr *mtrr_state = &vcpu->arch.mtrr_state;
 709         struct mtrr_iter iter;
 710         u64 start, end;
 711         int type = -1;
 712
 713         start = gfn_to_gpa(gfn);
 714         end = gfn_to_gpa(gfn + page_num);
 715         mtrr_for_each_mem_type(&iter, mtrr_state, start, end) {
 716                 if (type == -1) {
 717                         type = iter.mem_type;
 718                         continue;
 719                 }
 720
 721                 if (type != iter.mem_type)
 722                         return false;
 723         }
 724
 725         if (iter.mtrr_disabled)
 726                 return true;
 727
 728         if (!iter.partial_map)
 729                 return true;
 730
 731         if (type == -1)
 732                 return true;
 733
 734         return type == mtrr_default_type(mtrr_state);
 735 }