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         case 0x2f8:
  48                 return true;
  49         }
  50         return false;
  51 }
  52
  53 static bool valid_pat_type(unsigned t)
  54 {
  55         return t < 8 && (1 << t) & 0xf3; /* 0, 1, 4, 5, 6, 7 */
  56 }
  57
  58 static bool valid_mtrr_type(unsigned t)
  59 {
  60         return t < 8 && (1 << t) & 0x73; /* 0, 1, 4, 5, 6 */
  61 }
  62
  63 bool kvm_mtrr_valid(struct kvm_vcpu *vcpu, u32 msr, u64 data)
  64 {
  65         int i;
  66         u64 mask;
  67
  68         if (!msr_mtrr_valid(msr))
  69                 return false;
  70
  71         if (msr == MSR_IA32_CR_PAT) {
  72                 for (i = 0; i < 8; i++)
  73                         if (!valid_pat_type((data >> (i * 8)) & 0xff))
  74                                 return false;
  75                 return true;
  76         } else if (msr == MSR_MTRRdefType) {
  77                 if (data & ~0xcff)
  78                         return false;
  79                 return valid_mtrr_type(data & 0xff);
  80         } else if (msr >= MSR_MTRRfix64K_00000 && msr <= MSR_MTRRfix4K_F8000) {
  81                 for (i = 0; i < 8 ; i++)
  82                         if (!valid_mtrr_type((data >> (i * 8)) & 0xff))
  83                                 return false;
  84                 return true;
  85         }
  86
  87         /* variable MTRRs */
  88         WARN_ON(!(msr >= 0x200 && msr < 0x200 + 2 * KVM_NR_VAR_MTRR));
  89
  90         mask = (~0ULL) << cpuid_maxphyaddr(vcpu);
  91         if ((msr & 1) == 0) {
  92                 /* MTRR base */
  93                 if (!valid_mtrr_type(data & 0xff))
  94                         return false;
  95                 mask |= 0xf00;
  96         } else
  97                 /* MTRR mask */
  98                 mask |= 0x7ff;
  99         if (data & mask) {
 100                 kvm_inject_gp(vcpu, 0);
 101                 return false;
 102         }
 103
 104         return true;
 105 }
 106 EXPORT_SYMBOL_GPL(kvm_mtrr_valid);
 107
 108 static bool mtrr_is_enabled(struct kvm_mtrr *mtrr_state)
 109 {
 110         return !!(mtrr_state->deftype & IA32_MTRR_DEF_TYPE_E);
 111 }
 112
 113 static bool fixed_mtrr_is_enabled(struct kvm_mtrr *mtrr_state)
 114 {
 115         return !!(mtrr_state->deftype & IA32_MTRR_DEF_TYPE_FE);
 116 }
 117
 118 static u8 mtrr_default_type(struct kvm_mtrr *mtrr_state)
 119 {
 120         return mtrr_state->deftype & IA32_MTRR_DEF_TYPE_TYPE_MASK;
 121 }
 122
 123 /*
 124 * Three terms are used in the following code:
 125 * - segment, it indicates the address segments covered by fixed MTRRs.
 126 * - unit, it corresponds to the MSR entry in the segment.
 127 * - range, a range is covered in one memory cache type.
 128 */
 129 struct fixed_mtrr_segment {
 130         u64 start;
 131         u64 end;
 132
 133         int range_shift;
 134
 135         /* the start position in kvm_mtrr.fixed_ranges[]. */
 136         int range_start;
 137 };
 138
 139 static struct fixed_mtrr_segment fixed_seg_table[] = {
 140         /* MSR_MTRRfix64K_00000, 1 unit. 64K fixed mtrr. */
 141         {
 142                 .start = 0x0,
 143                 .end = 0x80000,
 144                 .range_shift = 16, /* 64K */
 145                 .range_start = 0,
 146         },
 147
 148         /*
 149          * MSR_MTRRfix16K_80000 ... MSR_MTRRfix16K_A0000, 2 units,
 150          * 16K fixed mtrr.
 151          */
 152         {
 153                 .start = 0x80000,
 154                 .end = 0xc0000,
 155                 .range_shift = 14, /* 16K */
 156                 .range_start = 8,
 157         },
 158
 159         /*
 160          * MSR_MTRRfix4K_C0000 ... MSR_MTRRfix4K_F8000, 8 units,
 161          * 4K fixed mtrr.
 162          */
 163         {
 164                 .start = 0xc0000,
 165                 .end = 0x100000,
 166                 .range_shift = 12, /* 12K */
 167                 .range_start = 24,
 168         }
 169 };
 170
 171 /*
 172  * The size of unit is covered in one MSR, one MSR entry contains
 173  * 8 ranges so that unit size is always 8 * 2^range_shift.
 174  */
 175 static u64 fixed_mtrr_seg_unit_size(int seg)
 176 {
 177         return 8 << fixed_seg_table[seg].range_shift;
 178 }
 179
 180 static bool fixed_msr_to_seg_unit(u32 msr, int *seg, int *unit)
 181 {
 182         switch (msr) {
 183         case MSR_MTRRfix64K_00000:
 184                 *seg = 0;
 185                 *unit = 0;
 186                 break;
 187         case MSR_MTRRfix16K_80000 ... MSR_MTRRfix16K_A0000:
 188                 *seg = 1;
 189                 *unit = msr - MSR_MTRRfix16K_80000;
 190                 break;
 191         case MSR_MTRRfix4K_C0000 ... MSR_MTRRfix4K_F8000:
 192                 *seg = 2;
 193                 *unit = msr - MSR_MTRRfix4K_C0000;
 194                 break;
 195         default:
 196                 return false;
 197         }
 198
 199         return true;
 200 }
 201
 202 static void fixed_mtrr_seg_unit_range(int seg, int unit, u64 *start, u64 *end)
 203 {
 204         struct fixed_mtrr_segment *mtrr_seg = &fixed_seg_table[seg];
 205         u64 unit_size = fixed_mtrr_seg_unit_size(seg);
 206
 207         *start = mtrr_seg->start + unit * unit_size;
 208         *end = *start + unit_size;
 209         WARN_ON(*end > mtrr_seg->end);
 210 }
 211
 212 static int fixed_mtrr_seg_unit_range_index(int seg, int unit)
 213 {
 214         struct fixed_mtrr_segment *mtrr_seg = &fixed_seg_table[seg];
 215
 216         WARN_ON(mtrr_seg->start + unit * fixed_mtrr_seg_unit_size(seg)
 217                 > mtrr_seg->end);
 218
 219         /* each unit has 8 ranges. */
 220         return mtrr_seg->range_start + 8 * unit;
 221 }
 222
 223 static int fixed_mtrr_seg_end_range_index(int seg)
 224 {
 225         struct fixed_mtrr_segment *mtrr_seg = &fixed_seg_table[seg];
 226         int n;
 227
 228         n = (mtrr_seg->end - mtrr_seg->start) >> mtrr_seg->range_shift;
 229         return mtrr_seg->range_start + n - 1;
 230 }
 231
 232 static bool fixed_msr_to_range(u32 msr, u64 *start, u64 *end)
 233 {
 234         int seg, unit;
 235
 236         if (!fixed_msr_to_seg_unit(msr, &seg, &unit))
 237                 return false;
 238
 239         fixed_mtrr_seg_unit_range(seg, unit, start, end);
 240         return true;
 241 }
 242
 243 static int fixed_msr_to_range_index(u32 msr)
 244 {
 245         int seg, unit;
 246
 247         if (!fixed_msr_to_seg_unit(msr, &seg, &unit))
 248                 return -1;
 249
 250         return fixed_mtrr_seg_unit_range_index(seg, unit);
 251 }
 252
 253 static int fixed_mtrr_addr_to_seg(u64 addr)
 254 {
 255         struct fixed_mtrr_segment *mtrr_seg;
 256         int seg, seg_num = ARRAY_SIZE(fixed_seg_table);
 257
 258         for (seg = 0; seg < seg_num; seg++) {
 259                 mtrr_seg = &fixed_seg_table[seg];
 260                 if (mtrr_seg->start >= addr && addr < mtrr_seg->end)
 261                         return seg;
 262         }
 263
 264         return -1;
 265 }
 266
 267 static int fixed_mtrr_addr_seg_to_range_index(u64 addr, int seg)
 268 {
 269         struct fixed_mtrr_segment *mtrr_seg;
 270         int index;
 271
 272         mtrr_seg = &fixed_seg_table[seg];
 273         index = mtrr_seg->range_start;
 274         index += (addr - mtrr_seg->start) >> mtrr_seg->range_shift;
 275         return index;
 276 }
 277
 278 static u64 fixed_mtrr_range_end_addr(int seg, int index)
 279 {
 280         struct fixed_mtrr_segment *mtrr_seg = &fixed_seg_table[seg];
 281         int pos = index - mtrr_seg->range_start;
 282
 283         return mtrr_seg->start + ((pos + 1) << mtrr_seg->range_shift);
 284 }
 285
 286 static void var_mtrr_range(struct kvm_mtrr_range *range, u64 *start, u64 *end)
 287 {
 288         u64 mask;
 289
 290         *start = range->base & PAGE_MASK;
 291
 292         mask = range->mask & PAGE_MASK;
 293         mask |= ~0ULL << boot_cpu_data.x86_phys_bits;
 294
 295         /* This cannot overflow because writing to the reserved bits of
 296          * variable MTRRs causes a #GP.
 297          */
 298         *end = (*start | ~mask) + 1;
 299 }
 300
 301 static void update_mtrr(struct kvm_vcpu *vcpu, u32 msr)
 302 {
 303         struct kvm_mtrr *mtrr_state = &vcpu->arch.mtrr_state;
 304         gfn_t start, end;
 305         int index;
 306
 307         if (msr == MSR_IA32_CR_PAT || !tdp_enabled ||
 308               !kvm_arch_has_noncoherent_dma(vcpu->kvm))
 309                 return;
 310
 311         if (!mtrr_is_enabled(mtrr_state) && msr != MSR_MTRRdefType)
 312                 return;
 313
 314         /* fixed MTRRs. */
 315         if (fixed_msr_to_range(msr, &start, &end)) {
 316                 if (!fixed_mtrr_is_enabled(mtrr_state))
 317                         return;
 318         } else if (msr == MSR_MTRRdefType) {
 319                 start = 0x0;
 320                 end = ~0ULL;
 321         } else {
 322                 /* variable range MTRRs. */
 323                 index = (msr - 0x200) / 2;
 324                 var_mtrr_range(&mtrr_state->var_ranges[index], &start, &end);
 325         }
 326
 327         kvm_zap_gfn_range(vcpu->kvm, gpa_to_gfn(start), gpa_to_gfn(end));
 328 }
 329
 330 static bool var_mtrr_range_is_valid(struct kvm_mtrr_range *range)
 331 {
 332         return (range->mask & (1 << 11)) != 0;
 333 }
 334
 335 static void set_var_mtrr_msr(struct kvm_vcpu *vcpu, u32 msr, u64 data)
 336 {
 337         struct kvm_mtrr *mtrr_state = &vcpu->arch.mtrr_state;
 338         struct kvm_mtrr_range *tmp, *cur;
 339         int index, is_mtrr_mask;
 340
 341         index = (msr - 0x200) / 2;
 342         is_mtrr_mask = msr - 0x200 - 2 * index;
 343         cur = &mtrr_state->var_ranges[index];
 344
 345         /* remove the entry if it's in the list. */
 346         if (var_mtrr_range_is_valid(cur))
 347                 list_del(&mtrr_state->var_ranges[index].node);
 348
 349         if (!is_mtrr_mask)
 350                 cur->base = data;
 351         else
 352                 cur->mask = data;
 353
 354         /* add it to the list if it's enabled. */
 355         if (var_mtrr_range_is_valid(cur)) {
 356                 list_for_each_entry(tmp, &mtrr_state->head, node)
 357                         if (cur->base >= tmp->base)
 358                                 break;
 359                 list_add_tail(&cur->node, &tmp->node);
 360         }
 361 }
 362
 363 int kvm_mtrr_set_msr(struct kvm_vcpu *vcpu, u32 msr, u64 data)
 364 {
 365         int index;
 366
 367         if (!kvm_mtrr_valid(vcpu, msr, data))
 368                 return 1;
 369
 370         index = fixed_msr_to_range_index(msr);
 371         if (index >= 0)
 372                 *(u64 *)&vcpu->arch.mtrr_state.fixed_ranges[index] = data;
 373         else if (msr == MSR_MTRRdefType)
 374                 vcpu->arch.mtrr_state.deftype = data;
 375         else if (msr == MSR_IA32_CR_PAT)
 376                 vcpu->arch.pat = data;
 377         else
 378                 set_var_mtrr_msr(vcpu, msr, data);
 379
 380         update_mtrr(vcpu, msr);
 381         return 0;
 382 }
 383
 384 int kvm_mtrr_get_msr(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata)
 385 {
 386         int index;
 387
 388         /* MSR_MTRRcap is a readonly MSR. */
 389         if (msr == MSR_MTRRcap) {
 390                 /*
 391                  * SMRR = 0
 392                  * WC = 1
 393                  * FIX = 1
 394                  * VCNT = KVM_NR_VAR_MTRR
 395                  */
 396                 *pdata = 0x500 | KVM_NR_VAR_MTRR;
 397                 return 0;
 398         }
 399
 400         if (!msr_mtrr_valid(msr))
 401                 return 1;
 402
 403         index = fixed_msr_to_range_index(msr);
 404         if (index >= 0)
 405                 *pdata = *(u64 *)&vcpu->arch.mtrr_state.fixed_ranges[index];
 406         else if (msr == MSR_MTRRdefType)
 407                 *pdata = vcpu->arch.mtrr_state.deftype;
 408         else if (msr == MSR_IA32_CR_PAT)
 409                 *pdata = vcpu->arch.pat;
 410         else {  /* Variable MTRRs */
 411                 int is_mtrr_mask;
 412
 413                 index = (msr - 0x200) / 2;
 414                 is_mtrr_mask = msr - 0x200 - 2 * index;
 415                 if (!is_mtrr_mask)
 416                         *pdata = vcpu->arch.mtrr_state.var_ranges[index].base;
 417                 else
 418                         *pdata = vcpu->arch.mtrr_state.var_ranges[index].mask;
 419         }
 420
 421         return 0;
 422 }
 423
 424 void kvm_vcpu_mtrr_init(struct kvm_vcpu *vcpu)
 425 {
 426         INIT_LIST_HEAD(&vcpu->arch.mtrr_state.head);
 427 }
 428
 429 struct mtrr_iter {
 430         /* input fields. */
 431         struct kvm_mtrr *mtrr_state;
 432         u64 start;
 433         u64 end;
 434
 435         /* output fields. */
 436         int mem_type;
 437         /* [start, end) is not fully covered in MTRRs? */
 438         bool partial_map;
 439
 440         /* private fields. */
 441         union {
 442                 /* used for fixed MTRRs. */
 443                 struct {
 444                         int index;
 445                         int seg;
 446                 };
 447
 448                 /* used for var MTRRs. */
 449                 struct {
 450                         struct kvm_mtrr_range *range;
 451                         /* max address has been covered in var MTRRs. */
 452                         u64 start_max;
 453                 };
 454         };
 455
 456         bool fixed;
 457 };
 458
 459 static bool mtrr_lookup_fixed_start(struct mtrr_iter *iter)
 460 {
 461         int seg, index;
 462
 463         if (!fixed_mtrr_is_enabled(iter->mtrr_state))
 464                 return false;
 465
 466         seg = fixed_mtrr_addr_to_seg(iter->start);
 467         if (seg < 0)
 468                 return false;
 469
 470         iter->fixed = true;
 471         index = fixed_mtrr_addr_seg_to_range_index(iter->start, seg);
 472         iter->index = index;
 473         iter->seg = seg;
 474         return true;
 475 }
 476
 477 static bool match_var_range(struct mtrr_iter *iter,
 478                             struct kvm_mtrr_range *range)
 479 {
 480         u64 start, end;
 481
 482         var_mtrr_range(range, &start, &end);
 483         if (!(start >= iter->end || end <= iter->start)) {
 484                 iter->range = range;
 485
 486                 /*
 487                  * the function is called when we do kvm_mtrr.head walking.
 488                  * Range has the minimum base address which interleaves
 489                  * [looker->start_max, looker->end).
 490                  */
 491                 iter->partial_map |= iter->start_max < start;
 492
 493                 /* update the max address has been covered. */
 494                 iter->start_max = max(iter->start_max, end);
 495                 return true;
 496         }
 497
 498         return false;
 499 }
 500
 501 static void __mtrr_lookup_var_next(struct mtrr_iter *iter)
 502 {
 503         struct kvm_mtrr *mtrr_state = iter->mtrr_state;
 504
 505         list_for_each_entry_continue(iter->range, &mtrr_state->head, node)
 506                 if (match_var_range(iter, iter->range))
 507                         return;
 508
 509         iter->range = NULL;
 510         iter->partial_map |= iter->start_max < iter->end;
 511 }
 512
 513 static void mtrr_lookup_var_start(struct mtrr_iter *iter)
 514 {
 515         struct kvm_mtrr *mtrr_state = iter->mtrr_state;
 516
 517         iter->fixed = false;
 518         iter->start_max = iter->start;
 519         iter->range = list_prepare_entry(iter->range, &mtrr_state->head, node);
 520
 521         __mtrr_lookup_var_next(iter);
 522 }
 523
 524 static void mtrr_lookup_fixed_next(struct mtrr_iter *iter)
 525 {
 526         /* terminate the lookup. */
 527         if (fixed_mtrr_range_end_addr(iter->seg, iter->index) >= iter->end) {
 528                 iter->fixed = false;
 529                 iter->range = NULL;
 530                 return;
 531         }
 532
 533         iter->index++;
 534
 535         /* have looked up for all fixed MTRRs. */
 536         if (iter->index >= ARRAY_SIZE(iter->mtrr_state->fixed_ranges))
 537                 return mtrr_lookup_var_start(iter);
 538
 539         /* switch to next segment. */
 540         if (iter->index > fixed_mtrr_seg_end_range_index(iter->seg))
 541                 iter->seg++;
 542 }
 543
 544 static void mtrr_lookup_var_next(struct mtrr_iter *iter)
 545 {
 546         __mtrr_lookup_var_next(iter);
 547 }
 548
 549 static void mtrr_lookup_start(struct mtrr_iter *iter)
 550 {
 551         if (!mtrr_is_enabled(iter->mtrr_state)) {
 552                 iter->partial_map = true;
 553                 return;
 554         }
 555
 556         if (!mtrr_lookup_fixed_start(iter))
 557                 mtrr_lookup_var_start(iter);
 558 }
 559
 560 static void mtrr_lookup_init(struct mtrr_iter *iter,
 561                              struct kvm_mtrr *mtrr_state, u64 start, u64 end)
 562 {
 563         iter->mtrr_state = mtrr_state;
 564         iter->start = start;
 565         iter->end = end;
 566         iter->partial_map = false;
 567         iter->fixed = false;
 568         iter->range = NULL;
 569
 570         mtrr_lookup_start(iter);
 571 }
 572
 573 static bool mtrr_lookup_okay(struct mtrr_iter *iter)
 574 {
 575         if (iter->fixed) {
 576                 iter->mem_type = iter->mtrr_state->fixed_ranges[iter->index];
 577                 return true;
 578         }
 579
 580         if (iter->range) {
 581                 iter->mem_type = iter->range->base & 0xff;
 582                 return true;
 583         }
 584
 585         return false;
 586 }
 587
 588 static void mtrr_lookup_next(struct mtrr_iter *iter)
 589 {
 590         if (iter->fixed)
 591                 mtrr_lookup_fixed_next(iter);
 592         else
 593                 mtrr_lookup_var_next(iter);
 594 }
 595
 596 #define mtrr_for_each_mem_type(_iter_, _mtrr_, _gpa_start_, _gpa_end_) \
 597         for (mtrr_lookup_init(_iter_, _mtrr_, _gpa_start_, _gpa_end_); \
 598              mtrr_lookup_okay(_iter_); mtrr_lookup_next(_iter_))
 599
 600 u8 kvm_mtrr_get_guest_memory_type(struct kvm_vcpu *vcpu, gfn_t gfn)
 601 {
 602         struct kvm_mtrr *mtrr_state = &vcpu->arch.mtrr_state;
 603         struct mtrr_iter iter;
 604         u64 start, end;
 605         int type = -1;
 606         const int wt_wb_mask = (1 << MTRR_TYPE_WRBACK)
 607                                | (1 << MTRR_TYPE_WRTHROUGH);
 608
 609         start = gfn_to_gpa(gfn);
 610         end = start + PAGE_SIZE;
 611
 612         mtrr_for_each_mem_type(&iter, mtrr_state, start, end) {
 613                 int curr_type = iter.mem_type;
 614
 615                 /*
 616                  * Please refer to Intel SDM Volume 3: 11.11.4.1 MTRR
 617                  * Precedences.
 618                  */
 619
 620                 if (type == -1) {
 621                         type = curr_type;
 622                         continue;
 623                 }
 624
 625                 /*
 626                  * If two or more variable memory ranges match and the
 627                  * memory types are identical, then that memory type is
 628                  * used.
 629                  */
 630                 if (type == curr_type)
 631                         continue;
 632
 633                 /*
 634                  * If two or more variable memory ranges match and one of
 635                  * the memory types is UC, the UC memory type used.
 636                  */
 637                 if (curr_type == MTRR_TYPE_UNCACHABLE)
 638                         return MTRR_TYPE_UNCACHABLE;
 639
 640                 /*
 641                  * If two or more variable memory ranges match and the
 642                  * memory types are WT and WB, the WT memory type is used.
 643                  */
 644                 if (((1 << type) & wt_wb_mask) &&
 645                       ((1 << curr_type) & wt_wb_mask)) {
 646                         type = MTRR_TYPE_WRTHROUGH;
 647                         continue;
 648                 }
 649
 650                 /*
 651                  * For overlaps not defined by the above rules, processor
 652                  * behavior is undefined.
 653                  */
 654
 655                 /* We use WB for this undefined behavior. :( */
 656                 return MTRR_TYPE_WRBACK;
 657         }
 658
 659         /* It is not covered by MTRRs. */
 660         if (iter.partial_map) {
 661                 /*
 662                  * We just check one page, partially covered by MTRRs is
 663                  * impossible.
 664                  */
 665                 WARN_ON(type != -1);
 666                 type = mtrr_default_type(mtrr_state);
 667         }
 668         return type;
 669 }
 670 EXPORT_SYMBOL_GPL(kvm_mtrr_get_guest_memory_type);
 671
 672 bool kvm_mtrr_check_gfn_range_consistency(struct kvm_vcpu *vcpu, gfn_t gfn,
 673                                           int page_num)
 674 {
 675         struct kvm_mtrr *mtrr_state = &vcpu->arch.mtrr_state;
 676         struct mtrr_iter iter;
 677         u64 start, end;
 678         int type = -1;
 679
 680         start = gfn_to_gpa(gfn);
 681         end = gfn_to_gpa(gfn + page_num);
 682         mtrr_for_each_mem_type(&iter, mtrr_state, start, end) {
 683                 if (type == -1) {
 684                         type = iter.mem_type;
 685                         continue;
 686                 }
 687
 688                 if (type != iter.mem_type)
 689                         return false;
 690         }
 691
 692         if (!iter.partial_map)
 693                 return true;
 694
 695         if (type == -1)
 696                 return true;
 697
 698         return type == mtrr_default_type(mtrr_state);
 699 }