1 /* SPDX-License-Identifier: GPL-2.0-only */
2 /*
3 * Kernel-based Virtual Machine driver for Linux
4 *
5 * This module enables machines with Intel VT-x extensions to run virtual
6 * machines without emulation or binary translation.
7 *
8 * MMU support
9 *
10 * Copyright (C) 2006 Qumranet, Inc.
11 * Copyright 2010 Red Hat, Inc. and/or its affiliates.
12 *
13 * Authors:
14 * Yaniv Kamay <yaniv@qumranet.com>
15 * Avi Kivity <avi@qumranet.com>
16 */
17
18 /*
19 * The MMU needs to be able to access/walk 32-bit and 64-bit guest page tables,
20 * as well as guest EPT tables, so the code in this file is compiled thrice,
21 * once per guest PTE type. The per-type defines are #undef'd at the end.
22 */
23
24 #if PTTYPE == 64
25 #define pt_element_t u64
26 #define guest_walker guest_walker64
27 #define FNAME(name) paging##64_##name
28 #define PT_LEVEL_BITS 9
29 #define PT_GUEST_DIRTY_SHIFT PT_DIRTY_SHIFT
30 #define PT_GUEST_ACCESSED_SHIFT PT_ACCESSED_SHIFT
31 #define PT_HAVE_ACCESSED_DIRTY(mmu) true
32 #ifdef CONFIG_X86_64
33 #define PT_MAX_FULL_LEVELS PT64_ROOT_MAX_LEVEL
34 #else
35 #define PT_MAX_FULL_LEVELS 2
36 #endif
37 #elif PTTYPE == 32
38 #define pt_element_t u32
39 #define guest_walker guest_walker32
40 #define FNAME(name) paging##32_##name
41 #define PT_LEVEL_BITS 10
42 #define PT_MAX_FULL_LEVELS 2
43 #define PT_GUEST_DIRTY_SHIFT PT_DIRTY_SHIFT
44 #define PT_GUEST_ACCESSED_SHIFT PT_ACCESSED_SHIFT
45 #define PT_HAVE_ACCESSED_DIRTY(mmu) true
46
47 #define PT32_DIR_PSE36_SIZE 4
48 #define PT32_DIR_PSE36_SHIFT 13
49 #define PT32_DIR_PSE36_MASK \
50 (((1ULL << PT32_DIR_PSE36_SIZE) - 1) << PT32_DIR_PSE36_SHIFT)
51 #elif PTTYPE == PTTYPE_EPT
52 #define pt_element_t u64
53 #define guest_walker guest_walkerEPT
54 #define FNAME(name) ept_##name
55 #define PT_LEVEL_BITS 9
56 #define PT_GUEST_DIRTY_SHIFT 9
57 #define PT_GUEST_ACCESSED_SHIFT 8
58 #define PT_HAVE_ACCESSED_DIRTY(mmu) (!(mmu)->cpu_role.base.ad_disabled)
59 #define PT_MAX_FULL_LEVELS PT64_ROOT_MAX_LEVEL
60 #else
61 #error Invalid PTTYPE value
62 #endif
63
64 /* Common logic, but per-type values. These also need to be undefined. */
65 #define PT_BASE_ADDR_MASK ((pt_element_t)__PT_BASE_ADDR_MASK)
66 #define PT_LVL_ADDR_MASK(lvl) __PT_LVL_ADDR_MASK(PT_BASE_ADDR_MASK, lvl, PT_LEVEL_BITS)
67 #define PT_LVL_OFFSET_MASK(lvl) __PT_LVL_OFFSET_MASK(PT_BASE_ADDR_MASK, lvl, PT_LEVEL_BITS)
68 #define PT_INDEX(addr, lvl) __PT_INDEX(addr, lvl, PT_LEVEL_BITS)
69
70 #define PT_GUEST_DIRTY_MASK (1 << PT_GUEST_DIRTY_SHIFT)
71 #define PT_GUEST_ACCESSED_MASK (1 << PT_GUEST_ACCESSED_SHIFT)
72
73 #define gpte_to_gfn_lvl FNAME(gpte_to_gfn_lvl)
74 #define gpte_to_gfn(pte) gpte_to_gfn_lvl((pte), PG_LEVEL_4K)
75
76 /*
77 * The guest_walker structure emulates the behavior of the hardware page
78 * table walker.
79 */
80 struct guest_walker {
81 int level;
82 unsigned max_level;
83 gfn_t table_gfn[PT_MAX_FULL_LEVELS];
84 pt_element_t ptes[PT_MAX_FULL_LEVELS];
85 pt_element_t prefetch_ptes[PTE_PREFETCH_NUM];
86 gpa_t pte_gpa[PT_MAX_FULL_LEVELS];
87 pt_element_t __user *ptep_user[PT_MAX_FULL_LEVELS];
88 bool pte_writable[PT_MAX_FULL_LEVELS];
89 unsigned int pt_access[PT_MAX_FULL_LEVELS];
90 unsigned int pte_access;
91 gfn_t gfn;
92 struct x86_exception fault;
93 };
94
95 #if PTTYPE == 32
96 static inline gfn_t pse36_gfn_delta(u32 gpte)
97 {
98 int shift = 32 - PT32_DIR_PSE36_SHIFT - PAGE_SHIFT;
99
100 return (gpte & PT32_DIR_PSE36_MASK) << shift;
101 }
102 #endif
103
104 static gfn_t gpte_to_gfn_lvl(pt_element_t gpte, int lvl)
105 {
106 return (gpte & PT_LVL_ADDR_MASK(lvl)) >> PAGE_SHIFT;
107 }
108
109 static inline void FNAME(protect_clean_gpte)(struct kvm_mmu *mmu, unsigned *access,
110 unsigned gpte)
111 {
112 unsigned mask;
113
114 /* dirty bit is not supported, so no need to track it */
115 if (!PT_HAVE_ACCESSED_DIRTY(mmu))
116 return;
117
118 BUILD_BUG_ON(PT_WRITABLE_MASK != ACC_WRITE_MASK);
119
120 mask = (unsigned)~ACC_WRITE_MASK;
121 /* Allow write access to dirty gptes */
122 mask |= (gpte >> (PT_GUEST_DIRTY_SHIFT - PT_WRITABLE_SHIFT)) &
123 PT_WRITABLE_MASK;
124 *access &= mask;
125 }
126
127 static inline int FNAME(is_present_gpte)(unsigned long pte)
128 {
129 #if PTTYPE != PTTYPE_EPT
130 return pte & PT_PRESENT_MASK;
131 #else
132 return pte & 7;
133 #endif
134 }
135
136 static bool FNAME(is_bad_mt_xwr)(struct rsvd_bits_validate *rsvd_check, u64 gpte)
137 {
138 #if PTTYPE != PTTYPE_EPT
139 return false;
140 #else
141 return __is_bad_mt_xwr(rsvd_check, gpte);
142 #endif
143 }
144
145 static bool FNAME(is_rsvd_bits_set)(struct kvm_mmu *mmu, u64 gpte, int level)
146 {
147 return __is_rsvd_bits_set(&mmu->guest_rsvd_check, gpte, level) ||
148 FNAME(is_bad_mt_xwr)(&mmu->guest_rsvd_check, gpte);
149 }
150
151 static bool FNAME(prefetch_invalid_gpte)(struct kvm_vcpu *vcpu,
152 struct kvm_mmu_page *sp, u64 *spte,
153 u64 gpte)
154 {
155 if (!FNAME(is_present_gpte)(gpte))
156 goto no_present;
157
158 /* Prefetch only accessed entries (unless A/D bits are disabled). */
159 if (PT_HAVE_ACCESSED_DIRTY(vcpu->arch.mmu) &&
160 !(gpte & PT_GUEST_ACCESSED_MASK))
161 goto no_present;
162
163 if (FNAME(is_rsvd_bits_set)(vcpu->arch.mmu, gpte, PG_LEVEL_4K))
164 goto no_present;
165
166 return false;
167
168 no_present:
169 drop_spte(vcpu->kvm, spte);
170 return true;
171 }
172
173 /*
174 * For PTTYPE_EPT, a page table can be executable but not readable
175 * on supported processors. Therefore, set_spte does not automatically
176 * set bit 0 if execute only is supported. Here, we repurpose ACC_USER_MASK
177 * to signify readability since it isn't used in the EPT case
178 */
179 static inline unsigned FNAME(gpte_access)(u64 gpte)
180 {
181 unsigned access;
182 #if PTTYPE == PTTYPE_EPT
183 access = ((gpte & VMX_EPT_WRITABLE_MASK) ? ACC_WRITE_MASK : 0) |
184 ((gpte & VMX_EPT_EXECUTABLE_MASK) ? ACC_EXEC_MASK : 0) |
185 ((gpte & VMX_EPT_READABLE_MASK) ? ACC_USER_MASK : 0);
186 #else
187 BUILD_BUG_ON(ACC_EXEC_MASK != PT_PRESENT_MASK);
188 BUILD_BUG_ON(ACC_EXEC_MASK != 1);
189 access = gpte & (PT_WRITABLE_MASK | PT_USER_MASK | PT_PRESENT_MASK);
190 /* Combine NX with P (which is set here) to get ACC_EXEC_MASK. */
191 access ^= (gpte >> PT64_NX_SHIFT);
192 #endif
193
194 return access;
195 }
196
197 static int FNAME(update_accessed_dirty_bits)(struct kvm_vcpu *vcpu,
198 struct kvm_mmu *mmu,
199 struct guest_walker *walker,
200 gpa_t addr, int write_fault)
201 {
202 unsigned level, index;
203 pt_element_t pte, orig_pte;
204 pt_element_t __user *ptep_user;
205 gfn_t table_gfn;
206 int ret;
207
208 /* dirty/accessed bits are not supported, so no need to update them */
209 if (!PT_HAVE_ACCESSED_DIRTY(mmu))
210 return 0;
211
212 for (level = walker->max_level; level >= walker->level; --level) {
213 pte = orig_pte = walker->ptes[level - 1];
214 table_gfn = walker->table_gfn[level - 1];
215 ptep_user = walker->ptep_user[level - 1];
216 index = offset_in_page(ptep_user) / sizeof(pt_element_t);
217 if (!(pte & PT_GUEST_ACCESSED_MASK)) {
218 trace_kvm_mmu_set_accessed_bit(table_gfn, index, sizeof(pte));
219 pte |= PT_GUEST_ACCESSED_MASK;
220 }
221 if (level == walker->level && write_fault &&
222 !(pte & PT_GUEST_DIRTY_MASK)) {
223 trace_kvm_mmu_set_dirty_bit(table_gfn, index, sizeof(pte));
224 #if PTTYPE == PTTYPE_EPT
225 if (kvm_x86_ops.nested_ops->write_log_dirty(vcpu, addr))
226 return -EINVAL;
227 #endif
228 pte |= PT_GUEST_DIRTY_MASK;
229 }
230 if (pte == orig_pte)
231 continue;
232
233 /*
234 * If the slot is read-only, simply do not process the accessed
235 * and dirty bits. This is the correct thing to do if the slot
236 * is ROM, and page tables in read-as-ROM/write-as-MMIO slots
237 * are only supported if the accessed and dirty bits are already
238 * set in the ROM (so that MMIO writes are never needed).
239 *
240 * Note that NPT does not allow this at all and faults, since
241 * it always wants nested page table entries for the guest
242 * page tables to be writable. And EPT works but will simply
243 * overwrite the read-only memory to set the accessed and dirty
244 * bits.
245 */
246 if (unlikely(!walker->pte_writable[level - 1]))
247 continue;
248
249 ret = __try_cmpxchg_user(ptep_user, &orig_pte, pte, fault);
250 if (ret)
251 return ret;
252
253 kvm_vcpu_mark_page_dirty(vcpu, table_gfn);
254 walker->ptes[level - 1] = pte;
255 }
256 return 0;
257 }
258
259 static inline unsigned FNAME(gpte_pkeys)(struct kvm_vcpu *vcpu, u64 gpte)
260 {
261 unsigned pkeys = 0;
262 #if PTTYPE == 64
263 pte_t pte = {.pte = gpte};
264
265 pkeys = pte_flags_pkey(pte_flags(pte));
266 #endif
267 return pkeys;
268 }
269
270 static inline bool FNAME(is_last_gpte)(struct kvm_mmu *mmu,
271 unsigned int level, unsigned int gpte)
272 {
273 /*
274 * For EPT and PAE paging (both variants), bit 7 is either reserved at
275 * all level or indicates a huge page (ignoring CR3/EPTP). In either
276 * case, bit 7 being set terminates the walk.
277 */
278 #if PTTYPE == 32
279 /*
280 * 32-bit paging requires special handling because bit 7 is ignored if
281 * CR4.PSE=0, not reserved. Clear bit 7 in the gpte if the level is
282 * greater than the last level for which bit 7 is the PAGE_SIZE bit.
283 *
284 * The RHS has bit 7 set iff level < (2 + PSE). If it is clear, bit 7
285 * is not reserved and does not indicate a large page at this level,
286 * so clear PT_PAGE_SIZE_MASK in gpte if that is the case.
287 */
288 gpte &= level - (PT32_ROOT_LEVEL + mmu->cpu_role.ext.cr4_pse);
289 #endif
290 /*
291 * PG_LEVEL_4K always terminates. The RHS has bit 7 set
292 * iff level <= PG_LEVEL_4K, which for our purpose means
293 * level == PG_LEVEL_4K; set PT_PAGE_SIZE_MASK in gpte then.
294 */
295 gpte |= level - PG_LEVEL_4K - 1;
296
297 return gpte & PT_PAGE_SIZE_MASK;
298 }
299 /*
300 * Fetch a guest pte for a guest virtual address, or for an L2's GPA.
301 */
302 static int FNAME(walk_addr_generic)(struct guest_walker *walker,
303 struct kvm_vcpu *vcpu, struct kvm_mmu *mmu,
304 gpa_t addr, u64 access)
305 {
306 int ret;
307 pt_element_t pte;
308 pt_element_t __user *ptep_user;
309 gfn_t table_gfn;
310 u64 pt_access, pte_access;
311 unsigned index, accessed_dirty, pte_pkey;
312 u64 nested_access;
313 gpa_t pte_gpa;
314 bool have_ad;
315 int offset;
316 u64 walk_nx_mask = 0;
317 const int write_fault = access & PFERR_WRITE_MASK;
318 const int user_fault = access & PFERR_USER_MASK;
319 const int fetch_fault = access & PFERR_FETCH_MASK;
320 u16 errcode = 0;
321 gpa_t real_gpa;
322 gfn_t gfn;
323
324 trace_kvm_mmu_pagetable_walk(addr, access);
325 retry_walk:
326 walker->level = mmu->cpu_role.base.level;
327 pte = kvm_mmu_get_guest_pgd(vcpu, mmu);
328 have_ad = PT_HAVE_ACCESSED_DIRTY(mmu);
329
330 #if PTTYPE == 64
331 walk_nx_mask = 1ULL << PT64_NX_SHIFT;
332 if (walker->level == PT32E_ROOT_LEVEL) {
333 pte = mmu->get_pdptr(vcpu, (addr >> 30) & 3);
334 trace_kvm_mmu_paging_element(pte, walker->level);
335 if (!FNAME(is_present_gpte)(pte))
336 goto error;
337 --walker->level;
338 }
339 #endif
340 walker->max_level = walker->level;
341
342 /*
343 * FIXME: on Intel processors, loads of the PDPTE registers for PAE paging
344 * by the MOV to CR instruction are treated as reads and do not cause the
345 * processor to set the dirty flag in any EPT paging-structure entry.
346 */
347 nested_access = (have_ad ? PFERR_WRITE_MASK : 0) | PFERR_USER_MASK;
348
349 pte_access = ~0;
350
351 /*
352 * Queue a page fault for injection if this assertion fails, as callers
353 * assume that walker.fault contains sane info on a walk failure. I.e.
354 * avoid making the situation worse by inducing even worse badness
355 * between when the assertion fails and when KVM kicks the vCPU out to
356 * userspace (because the VM is bugged).
357 */
358 if (KVM_BUG_ON(is_long_mode(vcpu) && !is_pae(vcpu), vcpu->kvm))
359 goto error;
360
361 ++walker->level;
362
363 do {
364 struct kvm_memory_slot *slot;
365 unsigned long host_addr;
366
367 pt_access = pte_access;
368 --walker->level;
369
370 index = PT_INDEX(addr, walker->level);
371 table_gfn = gpte_to_gfn(pte);
372 offset = index * sizeof(pt_element_t);
373 pte_gpa = gfn_to_gpa(table_gfn) + offset;
374
375 BUG_ON(walker->level < 1);
376 walker->table_gfn[walker->level - 1] = table_gfn;
377 walker->pte_gpa[walker->level - 1] = pte_gpa;
378
379 real_gpa = kvm_translate_gpa(vcpu, mmu, gfn_to_gpa(table_gfn),
380 nested_access, &walker->fault);
381
382 /*
383 * FIXME: This can happen if emulation (for of an INS/OUTS
384 * instruction) triggers a nested page fault. The exit
385 * qualification / exit info field will incorrectly have
386 * "guest page access" as the nested page fault's cause,
387 * instead of "guest page structure access". To fix this,
388 * the x86_exception struct should be augmented with enough
389 * information to fix the exit_qualification or exit_info_1
390 * fields.
391 */
392 if (unlikely(real_gpa == INVALID_GPA))
393 return 0;
394
395 slot = kvm_vcpu_gfn_to_memslot(vcpu, gpa_to_gfn(real_gpa));
396 if (!kvm_is_visible_memslot(slot))
397 goto error;
398
399 host_addr = gfn_to_hva_memslot_prot(slot, gpa_to_gfn(real_gpa),
400 &walker->pte_writable[walker->level - 1]);
401 if (unlikely(kvm_is_error_hva(host_addr)))
402 goto error;
403
404 ptep_user = (pt_element_t __user *)((void *)host_addr + offset);
405 if (unlikely(__get_user(pte, ptep_user)))
406 goto error;
407 walker->ptep_user[walker->level - 1] = ptep_user;
408
409 trace_kvm_mmu_paging_element(pte, walker->level);
410
411 /*
412 * Inverting the NX it lets us AND it like other
413 * permission bits.
414 */
415 pte_access = pt_access & (pte ^ walk_nx_mask);
416
417 if (unlikely(!FNAME(is_present_gpte)(pte)))
418 goto error;
419
420 if (unlikely(FNAME(is_rsvd_bits_set)(mmu, pte, walker->level))) {
421 errcode = PFERR_RSVD_MASK | PFERR_PRESENT_MASK;
422 goto error;
423 }
424
425 walker->ptes[walker->level - 1] = pte;
426
427 /* Convert to ACC_*_MASK flags for struct guest_walker. */
428 walker->pt_access[walker->level - 1] = FNAME(gpte_access)(pt_access ^ walk_nx_mask);
429 } while (!FNAME(is_last_gpte)(mmu, walker->level, pte));
430
431 pte_pkey = FNAME(gpte_pkeys)(vcpu, pte);
432 accessed_dirty = have_ad ? pte_access & PT_GUEST_ACCESSED_MASK : 0;
433
434 /* Convert to ACC_*_MASK flags for struct guest_walker. */
435 walker->pte_access = FNAME(gpte_access)(pte_access ^ walk_nx_mask);
436 errcode = permission_fault(vcpu, mmu, walker->pte_access, pte_pkey, access);
437 if (unlikely(errcode))
438 goto error;
439
440 gfn = gpte_to_gfn_lvl(pte, walker->level);
441 gfn += (addr & PT_LVL_OFFSET_MASK(walker->level)) >> PAGE_SHIFT;
442
443 #if PTTYPE == 32
444 if (walker->level > PG_LEVEL_4K && is_cpuid_PSE36())
445 gfn += pse36_gfn_delta(pte);
446 #endif
447
448 real_gpa = kvm_translate_gpa(vcpu, mmu, gfn_to_gpa(gfn), access, &walker->fault);
449 if (real_gpa == INVALID_GPA)
450 return 0;
451
452 walker->gfn = real_gpa >> PAGE_SHIFT;
453
454 if (!write_fault)
455 FNAME(protect_clean_gpte)(mmu, &walker->pte_access, pte);
456 else
457 /*
458 * On a write fault, fold the dirty bit into accessed_dirty.
459 * For modes without A/D bits support accessed_dirty will be
460 * always clear.
461 */
462 accessed_dirty &= pte >>
463 (PT_GUEST_DIRTY_SHIFT - PT_GUEST_ACCESSED_SHIFT);
464
465 if (unlikely(!accessed_dirty)) {
466 ret = FNAME(update_accessed_dirty_bits)(vcpu, mmu, walker,
467 addr, write_fault);
468 if (unlikely(ret < 0))
469 goto error;
470 else if (ret)
471 goto retry_walk;
472 }
473
474 return 1;
475
476 error:
477 errcode |= write_fault | user_fault;
478 if (fetch_fault && (is_efer_nx(mmu) || is_cr4_smep(mmu)))
479 errcode |= PFERR_FETCH_MASK;
480
481 walker->fault.vector = PF_VECTOR;
482 walker->fault.error_code_valid = true;
483 walker->fault.error_code = errcode;
484
485 #if PTTYPE == PTTYPE_EPT
486 /*
487 * Use PFERR_RSVD_MASK in error_code to tell if EPT
488 * misconfiguration requires to be injected. The detection is
489 * done by is_rsvd_bits_set() above.
490 *
491 * We set up the value of exit_qualification to inject:
492 * [2:0] - Derive from the access bits. The exit_qualification might be
493 * out of date if it is serving an EPT misconfiguration.
494 * [5:3] - Calculated by the page walk of the guest EPT page tables
495 * [7:8] - Derived from [7:8] of real exit_qualification
496 *
497 * The other bits are set to 0.
498 */
499 if (!(errcode & PFERR_RSVD_MASK)) {
500 walker->fault.exit_qualification = 0;
501
502 if (write_fault)
503 walker->fault.exit_qualification |= EPT_VIOLATION_ACC_WRITE;
504 if (user_fault)
505 walker->fault.exit_qualification |= EPT_VIOLATION_ACC_READ;
506 if (fetch_fault)
507 walker->fault.exit_qualification |= EPT_VIOLATION_ACC_INSTR;
508
509 /*
510 * Note, pte_access holds the raw RWX bits from the EPTE, not
511 * ACC_*_MASK flags!
512 */
513 walker->fault.exit_qualification |= (pte_access & VMX_EPT_RWX_MASK) <<
514 EPT_VIOLATION_RWX_SHIFT;
515 }
516 #endif
517 walker->fault.address = addr;
518 walker->fault.nested_page_fault = mmu != vcpu->arch.walk_mmu;
519 walker->fault.async_page_fault = false;
520
521 trace_kvm_mmu_walker_error(walker->fault.error_code);
522 return 0;
523 }
524
525 static int FNAME(walk_addr)(struct guest_walker *walker,
526 struct kvm_vcpu *vcpu, gpa_t addr, u64 access)
527 {
528 return FNAME(walk_addr_generic)(walker, vcpu, vcpu->arch.mmu, addr,
529 access);
530 }
531
532 static bool
533 FNAME(prefetch_gpte)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp,
534 u64 *spte, pt_element_t gpte)
535 {
536 struct kvm_memory_slot *slot;
537 unsigned pte_access;
538 gfn_t gfn;
539 kvm_pfn_t pfn;
540
541 if (FNAME(prefetch_invalid_gpte)(vcpu, sp, spte, gpte))
542 return false;
543
544 gfn = gpte_to_gfn(gpte);
545 pte_access = sp->role.access & FNAME(gpte_access)(gpte);
546 FNAME(protect_clean_gpte)(vcpu->arch.mmu, &pte_access, gpte);
547
548 slot = gfn_to_memslot_dirty_bitmap(vcpu, gfn, pte_access & ACC_WRITE_MASK);
549 if (!slot)
550 return false;
551
552 pfn = gfn_to_pfn_memslot_atomic(slot, gfn);
553 if (is_error_pfn(pfn))
554 return false;
555
556 mmu_set_spte(vcpu, slot, spte, pte_access, gfn, pfn, NULL);
557 kvm_release_pfn_clean(pfn);
558 return true;
559 }
560
561 static bool FNAME(gpte_changed)(struct kvm_vcpu *vcpu,
562 struct guest_walker *gw, int level)
563 {
564 pt_element_t curr_pte;
565 gpa_t base_gpa, pte_gpa = gw->pte_gpa[level - 1];
566 u64 mask;
567 int r, index;
568
569 if (level == PG_LEVEL_4K) {
570 mask = PTE_PREFETCH_NUM * sizeof(pt_element_t) - 1;
571 base_gpa = pte_gpa & ~mask;
572 index = (pte_gpa - base_gpa) / sizeof(pt_element_t);
573
574 r = kvm_vcpu_read_guest_atomic(vcpu, base_gpa,
575 gw->prefetch_ptes, sizeof(gw->prefetch_ptes));
576 curr_pte = gw->prefetch_ptes[index];
577 } else
578 r = kvm_vcpu_read_guest_atomic(vcpu, pte_gpa,
579 &curr_pte, sizeof(curr_pte));
580
581 return r || curr_pte != gw->ptes[level - 1];
582 }
583
584 static void FNAME(pte_prefetch)(struct kvm_vcpu *vcpu, struct guest_walker *gw,
585 u64 *sptep)
586 {
587 struct kvm_mmu_page *sp;
588 pt_element_t *gptep = gw->prefetch_ptes;
589 u64 *spte;
590 int i;
591
592 sp = sptep_to_sp(sptep);
593
594 if (sp->role.level > PG_LEVEL_4K)
595 return;
596
597 /*
598 * If addresses are being invalidated, skip prefetching to avoid
599 * accidentally prefetching those addresses.
600 */
601 if (unlikely(vcpu->kvm->mmu_invalidate_in_progress))
602 return;
603
604 if (sp->role.direct)
605 return __direct_pte_prefetch(vcpu, sp, sptep);
606
607 i = spte_index(sptep) & ~(PTE_PREFETCH_NUM - 1);
608 spte = sp->spt + i;
609
610 for (i = 0; i < PTE_PREFETCH_NUM; i++, spte++) {
611 if (spte == sptep)
612 continue;
613
614 if (is_shadow_present_pte(*spte))
615 continue;
616
617 if (!FNAME(prefetch_gpte)(vcpu, sp, spte, gptep[i]))
618 break;
619 }
620 }
621
622 /*
623 * Fetch a shadow pte for a specific level in the paging hierarchy.
624 * If the guest tries to write a write-protected page, we need to
625 * emulate this operation, return 1 to indicate this case.
626 */
627 static int FNAME(fetch)(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault,
628 struct guest_walker *gw)
629 {
630 struct kvm_mmu_page *sp = NULL;
631 struct kvm_shadow_walk_iterator it;
632 unsigned int direct_access, access;
633 int top_level, ret;
634 gfn_t base_gfn = fault->gfn;
635
636 WARN_ON_ONCE(gw->gfn != base_gfn);
637 direct_access = gw->pte_access;
638
639 top_level = vcpu->arch.mmu->cpu_role.base.level;
640 if (top_level == PT32E_ROOT_LEVEL)
641 top_level = PT32_ROOT_LEVEL;
642 /*
643 * Verify that the top-level gpte is still there. Since the page
644 * is a root page, it is either write protected (and cannot be
645 * changed from now on) or it is invalid (in which case, we don't
646 * really care if it changes underneath us after this point).
647 */
648 if (FNAME(gpte_changed)(vcpu, gw, top_level))
649 goto out_gpte_changed;
650
651 if (WARN_ON_ONCE(!VALID_PAGE(vcpu->arch.mmu->root.hpa)))
652 goto out_gpte_changed;
653
654 /*
655 * Load a new root and retry the faulting instruction in the extremely
656 * unlikely scenario that the guest root gfn became visible between
657 * loading a dummy root and handling the resulting page fault, e.g. if
658 * userspace create a memslot in the interim.
659 */
660 if (unlikely(kvm_mmu_is_dummy_root(vcpu->arch.mmu->root.hpa))) {
661 kvm_make_request(KVM_REQ_MMU_FREE_OBSOLETE_ROOTS, vcpu);
662 goto out_gpte_changed;
663 }
664
665 for_each_shadow_entry(vcpu, fault->addr, it) {
666 gfn_t table_gfn;
667
668 clear_sp_write_flooding_count(it.sptep);
669 if (it.level == gw->level)
670 break;
671
672 table_gfn = gw->table_gfn[it.level - 2];
673 access = gw->pt_access[it.level - 2];
674 sp = kvm_mmu_get_child_sp(vcpu, it.sptep, table_gfn,
675 false, access);
676
677 if (sp != ERR_PTR(-EEXIST)) {
678 /*
679 * We must synchronize the pagetable before linking it
680 * because the guest doesn't need to flush tlb when
681 * the gpte is changed from non-present to present.
682 * Otherwise, the guest may use the wrong mapping.
683 *
684 * For PG_LEVEL_4K, kvm_mmu_get_page() has already
685 * synchronized it transiently via kvm_sync_page().
686 *
687 * For higher level pagetable, we synchronize it via
688 * the slower mmu_sync_children(). If it needs to
689 * break, some progress has been made; return
690 * RET_PF_RETRY and retry on the next #PF.
691 * KVM_REQ_MMU_SYNC is not necessary but it
692 * expedites the process.
693 */
694 if (sp->unsync_children &&
695 mmu_sync_children(vcpu, sp, false))
696 return RET_PF_RETRY;
697 }
698
699 /*
700 * Verify that the gpte in the page we've just write
701 * protected is still there.
702 */
703 if (FNAME(gpte_changed)(vcpu, gw, it.level - 1))
704 goto out_gpte_changed;
705
706 if (sp != ERR_PTR(-EEXIST))
707 link_shadow_page(vcpu, it.sptep, sp);
708
709 if (fault->write && table_gfn == fault->gfn)
710 fault->write_fault_to_shadow_pgtable = true;
711 }
712
713 /*
714 * Adjust the hugepage size _after_ resolving indirect shadow pages.
715 * KVM doesn't support mapping hugepages into the guest for gfns that
716 * are being shadowed by KVM, i.e. allocating a new shadow page may
717 * affect the allowed hugepage size.
718 */
719 kvm_mmu_hugepage_adjust(vcpu, fault);
720
721 trace_kvm_mmu_spte_requested(fault);
722
723 for (; shadow_walk_okay(&it); shadow_walk_next(&it)) {
724 /*
725 * We cannot overwrite existing page tables with an NX
726 * large page, as the leaf could be executable.
727 */
728 if (fault->nx_huge_page_workaround_enabled)
729 disallowed_hugepage_adjust(fault, *it.sptep, it.level);
730
731 base_gfn = gfn_round_for_level(fault->gfn, it.level);
732 if (it.level == fault->goal_level)
733 break;
734
735 validate_direct_spte(vcpu, it.sptep, direct_access);
736
737 sp = kvm_mmu_get_child_sp(vcpu, it.sptep, base_gfn,
738 true, direct_access);
739 if (sp == ERR_PTR(-EEXIST))
740 continue;
741
742 link_shadow_page(vcpu, it.sptep, sp);
743 if (fault->huge_page_disallowed)
744 account_nx_huge_page(vcpu->kvm, sp,
745 fault->req_level >= it.level);
746 }
747
748 if (WARN_ON_ONCE(it.level != fault->goal_level))
749 return -EFAULT;
750
751 ret = mmu_set_spte(vcpu, fault->slot, it.sptep, gw->pte_access,
752 base_gfn, fault->pfn, fault);
753 if (ret == RET_PF_SPURIOUS)
754 return ret;
755
756 FNAME(pte_prefetch)(vcpu, gw, it.sptep);
757 return ret;
758
759 out_gpte_changed:
760 return RET_PF_RETRY;
761 }
762
763 /*
764 * Page fault handler. There are several causes for a page fault:
765 * - there is no shadow pte for the guest pte
766 * - write access through a shadow pte marked read only so that we can set
767 * the dirty bit
768 * - write access to a shadow pte marked read only so we can update the page
769 * dirty bitmap, when userspace requests it
770 * - mmio access; in this case we will never install a present shadow pte
771 * - normal guest page fault due to the guest pte marked not present, not
772 * writable, or not executable
773 *
774 * Returns: 1 if we need to emulate the instruction, 0 otherwise, or
775 * a negative value on error.
776 */
777 static int FNAME(page_fault)(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault)
778 {
779 struct guest_walker walker;
780 int r;
781
782 WARN_ON_ONCE(fault->is_tdp);
783
784 /*
785 * Look up the guest pte for the faulting address.
786 * If PFEC.RSVD is set, this is a shadow page fault.
787 * The bit needs to be cleared before walking guest page tables.
788 */
789 r = FNAME(walk_addr)(&walker, vcpu, fault->addr,
790 fault->error_code & ~PFERR_RSVD_MASK);
791
792 /*
793 * The page is not mapped by the guest. Let the guest handle it.
794 */
795 if (!r) {
796 if (!fault->prefetch)
797 kvm_inject_emulated_page_fault(vcpu, &walker.fault);
798
799 return RET_PF_RETRY;
800 }
801
802 fault->gfn = walker.gfn;
803 fault->max_level = walker.level;
804 fault->slot = kvm_vcpu_gfn_to_memslot(vcpu, fault->gfn);
805
806 if (page_fault_handle_page_track(vcpu, fault)) {
807 shadow_page_table_clear_flood(vcpu, fault->addr);
808 return RET_PF_EMULATE;
809 }
810
811 r = mmu_topup_memory_caches(vcpu, true);
812 if (r)
813 return r;
814
815 r = kvm_faultin_pfn(vcpu, fault, walker.pte_access);
816 if (r != RET_PF_CONTINUE)
817 return r;
818
819 /*
820 * Do not change pte_access if the pfn is a mmio page, otherwise
821 * we will cache the incorrect access into mmio spte.
822 */
823 if (fault->write && !(walker.pte_access & ACC_WRITE_MASK) &&
824 !is_cr0_wp(vcpu->arch.mmu) && !fault->user && fault->slot) {
825 walker.pte_access |= ACC_WRITE_MASK;
826 walker.pte_access &= ~ACC_USER_MASK;
827
828 /*
829 * If we converted a user page to a kernel page,
830 * so that the kernel can write to it when cr0.wp=0,
831 * then we should prevent the kernel from executing it
832 * if SMEP is enabled.
833 */
834 if (is_cr4_smep(vcpu->arch.mmu))
835 walker.pte_access &= ~ACC_EXEC_MASK;
836 }
837
838 r = RET_PF_RETRY;
839 write_lock(&vcpu->kvm->mmu_lock);
840
841 if (is_page_fault_stale(vcpu, fault))
842 goto out_unlock;
843
844 r = make_mmu_pages_available(vcpu);
845 if (r)
846 goto out_unlock;
847 r = FNAME(fetch)(vcpu, fault, &walker);
848
849 out_unlock:
850 write_unlock(&vcpu->kvm->mmu_lock);
851 kvm_release_pfn_clean(fault->pfn);
852 return r;
853 }
854
855 static gpa_t FNAME(get_level1_sp_gpa)(struct kvm_mmu_page *sp)
856 {
857 int offset = 0;
858
859 WARN_ON_ONCE(sp->role.level != PG_LEVEL_4K);
860
861 if (PTTYPE == 32)
862 offset = sp->role.quadrant << SPTE_LEVEL_BITS;
863
864 return gfn_to_gpa(sp->gfn) + offset * sizeof(pt_element_t);
865 }
866
867 /* Note, @addr is a GPA when gva_to_gpa() translates an L2 GPA to an L1 GPA. */
868 static gpa_t FNAME(gva_to_gpa)(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu,
869 gpa_t addr, u64 access,
870 struct x86_exception *exception)
871 {
872 struct guest_walker walker;
873 gpa_t gpa = INVALID_GPA;
874 int r;
875
876 #ifndef CONFIG_X86_64
877 /* A 64-bit GVA should be impossible on 32-bit KVM. */
878 WARN_ON_ONCE((addr >> 32) && mmu == vcpu->arch.walk_mmu);
879 #endif
880
881 r = FNAME(walk_addr_generic)(&walker, vcpu, mmu, addr, access);
882
883 if (r) {
884 gpa = gfn_to_gpa(walker.gfn);
885 gpa |= addr & ~PAGE_MASK;
886 } else if (exception)
887 *exception = walker.fault;
888
889 return gpa;
890 }
891
892 /*
893 * Using the information in sp->shadowed_translation (kvm_mmu_page_get_gfn()) is
894 * safe because:
895 * - The spte has a reference to the struct page, so the pfn for a given gfn
896 * can't change unless all sptes pointing to it are nuked first.
897 *
898 * Returns
899 * < 0: failed to sync spte
900 * 0: the spte is synced and no tlb flushing is required
901 * > 0: the spte is synced and tlb flushing is required
902 */
903 static int FNAME(sync_spte)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp, int i)
904 {
905 bool host_writable;
906 gpa_t first_pte_gpa;
907 u64 *sptep, spte;
908 struct kvm_memory_slot *slot;
909 unsigned pte_access;
910 pt_element_t gpte;
911 gpa_t pte_gpa;
912 gfn_t gfn;
913
914 if (WARN_ON_ONCE(sp->spt[i] == SHADOW_NONPRESENT_VALUE ||
915 !sp->shadowed_translation))
916 return 0;
917
918 first_pte_gpa = FNAME(get_level1_sp_gpa)(sp);
919 pte_gpa = first_pte_gpa + i * sizeof(pt_element_t);
920
921 if (kvm_vcpu_read_guest_atomic(vcpu, pte_gpa, &gpte,
922 sizeof(pt_element_t)))
923 return -1;
924
925 if (FNAME(prefetch_invalid_gpte)(vcpu, sp, &sp->spt[i], gpte))
926 return 1;
927
928 gfn = gpte_to_gfn(gpte);
929 pte_access = sp->role.access;
930 pte_access &= FNAME(gpte_access)(gpte);
931 FNAME(protect_clean_gpte)(vcpu->arch.mmu, &pte_access, gpte);
932
933 if (sync_mmio_spte(vcpu, &sp->spt[i], gfn, pte_access))
934 return 0;
935
936 /*
937 * Drop the SPTE if the new protections result in no effective
938 * "present" bit or if the gfn is changing. The former case
939 * only affects EPT with execute-only support with pte_access==0;
940 * all other paging modes will create a read-only SPTE if
941 * pte_access is zero.
942 */
943 if ((pte_access | shadow_present_mask) == SHADOW_NONPRESENT_VALUE ||
944 gfn != kvm_mmu_page_get_gfn(sp, i)) {
945 drop_spte(vcpu->kvm, &sp->spt[i]);
946 return 1;
947 }
948 /*
949 * Do nothing if the permissions are unchanged. The existing SPTE is
950 * still, and prefetch_invalid_gpte() has verified that the A/D bits
951 * are set in the "new" gPTE, i.e. there is no danger of missing an A/D
952 * update due to A/D bits being set in the SPTE but not the gPTE.
953 */
954 if (kvm_mmu_page_get_access(sp, i) == pte_access)
955 return 0;
956
957 /* Update the shadowed access bits in case they changed. */
958 kvm_mmu_page_set_access(sp, i, pte_access);
959
960 sptep = &sp->spt[i];
961 spte = *sptep;
962 host_writable = spte & shadow_host_writable_mask;
963 slot = kvm_vcpu_gfn_to_memslot(vcpu, gfn);
964 make_spte(vcpu, sp, slot, pte_access, gfn,
965 spte_to_pfn(spte), spte, true, false,
966 host_writable, &spte);
967
968 return mmu_spte_update(sptep, spte);
969 }
970
971 #undef pt_element_t
972 #undef guest_walker
973 #undef FNAME
974 #undef PT_BASE_ADDR_MASK
975 #undef PT_INDEX
976 #undef PT_LVL_ADDR_MASK
977 #undef PT_LVL_OFFSET_MASK
978 #undef PT_LEVEL_BITS
979 #undef PT_MAX_FULL_LEVELS
980 #undef gpte_to_gfn
981 #undef gpte_to_gfn_lvl
982 #undef PT_GUEST_ACCESSED_MASK
983 #undef PT_GUEST_DIRTY_MASK
984 #undef PT_GUEST_DIRTY_SHIFT
985 #undef PT_GUEST_ACCESSED_SHIFT
986 #undef PT_HAVE_ACCESSED_DIRTY
987
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