1 /*
2 * Kernel-based Virtual Machine driver for Linux
3 *
4 * This module enables machines with Intel VT-x extensions to run virtual
5 * machines without emulation or binary translation.
6 *
7 * MMU support
8 *
9 * Copyright (C) 2006 Qumranet, Inc.
10 * Copyright 2010 Red Hat, Inc. and/or its affiliates.
11 *
12 * Authors:
13 * Yaniv Kamay <yaniv@qumranet.com>
14 * Avi Kivity <avi@qumranet.com>
15 *
16 * This work is licensed under the terms of the GNU GPL, version 2. See
17 * the COPYING file in the top-level directory.
18 *
19 */
20
21 /*
22 * We need the mmu code to access both 32-bit and 64-bit guest ptes,
23 * so the code in this file is compiled twice, once per pte size.
24 */
25
26 #if PTTYPE == 64
27 #define pt_element_t u64
28 #define guest_walker guest_walker64
29 #define FNAME(name) paging##64_##name
30 #define PT_BASE_ADDR_MASK PT64_BASE_ADDR_MASK
31 #define PT_LVL_ADDR_MASK(lvl) PT64_LVL_ADDR_MASK(lvl)
32 #define PT_LVL_OFFSET_MASK(lvl) PT64_LVL_OFFSET_MASK(lvl)
33 #define PT_INDEX(addr, level) PT64_INDEX(addr, level)
34 #define PT_LEVEL_BITS PT64_LEVEL_BITS
35 #define PT_GUEST_DIRTY_SHIFT PT_DIRTY_SHIFT
36 #define PT_GUEST_ACCESSED_SHIFT PT_ACCESSED_SHIFT
37 #define PT_HAVE_ACCESSED_DIRTY(mmu) true
38 #ifdef CONFIG_X86_64
39 #define PT_MAX_FULL_LEVELS 4
40 #define CMPXCHG cmpxchg
41 #else
42 #define CMPXCHG cmpxchg64
43 #define PT_MAX_FULL_LEVELS 2
44 #endif
45 #elif PTTYPE == 32
46 #define pt_element_t u32
47 #define guest_walker guest_walker32
48 #define FNAME(name) paging##32_##name
49 #define PT_BASE_ADDR_MASK PT32_BASE_ADDR_MASK
50 #define PT_LVL_ADDR_MASK(lvl) PT32_LVL_ADDR_MASK(lvl)
51 #define PT_LVL_OFFSET_MASK(lvl) PT32_LVL_OFFSET_MASK(lvl)
52 #define PT_INDEX(addr, level) PT32_INDEX(addr, level)
53 #define PT_LEVEL_BITS PT32_LEVEL_BITS
54 #define PT_MAX_FULL_LEVELS 2
55 #define PT_GUEST_DIRTY_SHIFT PT_DIRTY_SHIFT
56 #define PT_GUEST_ACCESSED_SHIFT PT_ACCESSED_SHIFT
57 #define PT_HAVE_ACCESSED_DIRTY(mmu) true
58 #define CMPXCHG cmpxchg
59 #elif PTTYPE == PTTYPE_EPT
60 #define pt_element_t u64
61 #define guest_walker guest_walkerEPT
62 #define FNAME(name) ept_##name
63 #define PT_BASE_ADDR_MASK PT64_BASE_ADDR_MASK
64 #define PT_LVL_ADDR_MASK(lvl) PT64_LVL_ADDR_MASK(lvl)
65 #define PT_LVL_OFFSET_MASK(lvl) PT64_LVL_OFFSET_MASK(lvl)
66 #define PT_INDEX(addr, level) PT64_INDEX(addr, level)
67 #define PT_LEVEL_BITS PT64_LEVEL_BITS
68 #define PT_GUEST_DIRTY_SHIFT 9
69 #define PT_GUEST_ACCESSED_SHIFT 8
70 #define PT_HAVE_ACCESSED_DIRTY(mmu) ((mmu)->ept_ad)
71 #define CMPXCHG cmpxchg64
72 #define PT_MAX_FULL_LEVELS 4
73 #else
74 #error Invalid PTTYPE value
75 #endif
76
77 #define PT_GUEST_DIRTY_MASK (1 << PT_GUEST_DIRTY_SHIFT)
78 #define PT_GUEST_ACCESSED_MASK (1 << PT_GUEST_ACCESSED_SHIFT)
79
80 #define gpte_to_gfn_lvl FNAME(gpte_to_gfn_lvl)
81 #define gpte_to_gfn(pte) gpte_to_gfn_lvl((pte), PT_PAGE_TABLE_LEVEL)
82
83 /*
84 * The guest_walker structure emulates the behavior of the hardware page
85 * table walker.
86 */
87 struct guest_walker {
88 int level;
89 unsigned max_level;
90 gfn_t table_gfn[PT_MAX_FULL_LEVELS];
91 pt_element_t ptes[PT_MAX_FULL_LEVELS];
92 pt_element_t prefetch_ptes[PTE_PREFETCH_NUM];
93 gpa_t pte_gpa[PT_MAX_FULL_LEVELS];
94 pt_element_t __user *ptep_user[PT_MAX_FULL_LEVELS];
95 bool pte_writable[PT_MAX_FULL_LEVELS];
96 unsigned pt_access;
97 unsigned pte_access;
98 gfn_t gfn;
99 struct x86_exception fault;
100 };
101
gpte_to_gfn_lvl(pt_element_t gpte,int lvl)102 static gfn_t gpte_to_gfn_lvl(pt_element_t gpte, int lvl)
103 {
104 return (gpte & PT_LVL_ADDR_MASK(lvl)) >> PAGE_SHIFT;
105 }
106
FNAME(protect_clean_gpte)107 static inline void FNAME(protect_clean_gpte)(struct kvm_mmu *mmu, unsigned *access,
108 unsigned gpte)
109 {
110 unsigned mask;
111
112 /* dirty bit is not supported, so no need to track it */
113 if (!PT_HAVE_ACCESSED_DIRTY(mmu))
114 return;
115
116 BUILD_BUG_ON(PT_WRITABLE_MASK != ACC_WRITE_MASK);
117
118 mask = (unsigned)~ACC_WRITE_MASK;
119 /* Allow write access to dirty gptes */
120 mask |= (gpte >> (PT_GUEST_DIRTY_SHIFT - PT_WRITABLE_SHIFT)) &
121 PT_WRITABLE_MASK;
122 *access &= mask;
123 }
124
FNAME(is_present_gpte)125 static inline int FNAME(is_present_gpte)(unsigned long pte)
126 {
127 #if PTTYPE != PTTYPE_EPT
128 return pte & PT_PRESENT_MASK;
129 #else
130 return pte & 7;
131 #endif
132 }
133
FNAME(cmpxchg_gpte)134 static int FNAME(cmpxchg_gpte)(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu,
135 pt_element_t __user *ptep_user, unsigned index,
136 pt_element_t orig_pte, pt_element_t new_pte)
137 {
138 int npages;
139 pt_element_t ret;
140 pt_element_t *table;
141 struct page *page;
142
143 npages = get_user_pages_fast((unsigned long)ptep_user, 1, 1, &page);
144 /* Check if the user is doing something meaningless. */
145 if (unlikely(npages != 1))
146 return -EFAULT;
147
148 table = kmap_atomic(page);
149 ret = CMPXCHG(&table[index], orig_pte, new_pte);
150 kunmap_atomic(table);
151
152 kvm_release_page_dirty(page);
153
154 return (ret != orig_pte);
155 }
156
FNAME(prefetch_invalid_gpte)157 static bool FNAME(prefetch_invalid_gpte)(struct kvm_vcpu *vcpu,
158 struct kvm_mmu_page *sp, u64 *spte,
159 u64 gpte)
160 {
161 if (is_rsvd_bits_set(&vcpu->arch.mmu, gpte, PT_PAGE_TABLE_LEVEL))
162 goto no_present;
163
164 if (!FNAME(is_present_gpte)(gpte))
165 goto no_present;
166
167 /* if accessed bit is not supported prefetch non accessed gpte */
168 if (PT_HAVE_ACCESSED_DIRTY(&vcpu->arch.mmu) && !(gpte & PT_GUEST_ACCESSED_MASK))
169 goto no_present;
170
171 return false;
172
173 no_present:
174 drop_spte(vcpu->kvm, spte);
175 return true;
176 }
177
178 /*
179 * For PTTYPE_EPT, a page table can be executable but not readable
180 * on supported processors. Therefore, set_spte does not automatically
181 * set bit 0 if execute only is supported. Here, we repurpose ACC_USER_MASK
182 * to signify readability since it isn't used in the EPT case
183 */
FNAME(gpte_access)184 static inline unsigned FNAME(gpte_access)(u64 gpte)
185 {
186 unsigned access;
187 #if PTTYPE == PTTYPE_EPT
188 access = ((gpte & VMX_EPT_WRITABLE_MASK) ? ACC_WRITE_MASK : 0) |
189 ((gpte & VMX_EPT_EXECUTABLE_MASK) ? ACC_EXEC_MASK : 0) |
190 ((gpte & VMX_EPT_READABLE_MASK) ? ACC_USER_MASK : 0);
191 #else
192 BUILD_BUG_ON(ACC_EXEC_MASK != PT_PRESENT_MASK);
193 BUILD_BUG_ON(ACC_EXEC_MASK != 1);
194 access = gpte & (PT_WRITABLE_MASK | PT_USER_MASK | PT_PRESENT_MASK);
195 /* Combine NX with P (which is set here) to get ACC_EXEC_MASK. */
196 access ^= (gpte >> PT64_NX_SHIFT);
197 #endif
198
199 return access;
200 }
201
FNAME(update_accessed_dirty_bits)202 static int FNAME(update_accessed_dirty_bits)(struct kvm_vcpu *vcpu,
203 struct kvm_mmu *mmu,
204 struct guest_walker *walker,
205 int write_fault)
206 {
207 unsigned level, index;
208 pt_element_t pte, orig_pte;
209 pt_element_t __user *ptep_user;
210 gfn_t table_gfn;
211 int ret;
212
213 /* dirty/accessed bits are not supported, so no need to update them */
214 if (!PT_HAVE_ACCESSED_DIRTY(mmu))
215 return 0;
216
217 for (level = walker->max_level; level >= walker->level; --level) {
218 pte = orig_pte = walker->ptes[level - 1];
219 table_gfn = walker->table_gfn[level - 1];
220 ptep_user = walker->ptep_user[level - 1];
221 index = offset_in_page(ptep_user) / sizeof(pt_element_t);
222 if (!(pte & PT_GUEST_ACCESSED_MASK)) {
223 trace_kvm_mmu_set_accessed_bit(table_gfn, index, sizeof(pte));
224 pte |= PT_GUEST_ACCESSED_MASK;
225 }
226 if (level == walker->level && write_fault &&
227 !(pte & PT_GUEST_DIRTY_MASK)) {
228 trace_kvm_mmu_set_dirty_bit(table_gfn, index, sizeof(pte));
229 #if PTTYPE == PTTYPE_EPT
230 if (kvm_arch_write_log_dirty(vcpu))
231 return -EINVAL;
232 #endif
233 pte |= PT_GUEST_DIRTY_MASK;
234 }
235 if (pte == orig_pte)
236 continue;
237
238 /*
239 * If the slot is read-only, simply do not process the accessed
240 * and dirty bits. This is the correct thing to do if the slot
241 * is ROM, and page tables in read-as-ROM/write-as-MMIO slots
242 * are only supported if the accessed and dirty bits are already
243 * set in the ROM (so that MMIO writes are never needed).
244 *
245 * Note that NPT does not allow this at all and faults, since
246 * it always wants nested page table entries for the guest
247 * page tables to be writable. And EPT works but will simply
248 * overwrite the read-only memory to set the accessed and dirty
249 * bits.
250 */
251 if (unlikely(!walker->pte_writable[level - 1]))
252 continue;
253
254 ret = FNAME(cmpxchg_gpte)(vcpu, mmu, ptep_user, index, orig_pte, pte);
255 if (ret)
256 return ret;
257
258 kvm_vcpu_mark_page_dirty(vcpu, table_gfn);
259 walker->ptes[level - 1] = pte;
260 }
261 return 0;
262 }
263
FNAME(gpte_pkeys)264 static inline unsigned FNAME(gpte_pkeys)(struct kvm_vcpu *vcpu, u64 gpte)
265 {
266 unsigned pkeys = 0;
267 #if PTTYPE == 64
268 pte_t pte = {.pte = gpte};
269
270 pkeys = pte_flags_pkey(pte_flags(pte));
271 #endif
272 return pkeys;
273 }
274
275 /*
276 * Fetch a guest pte for a guest virtual address
277 */
FNAME(walk_addr_generic)278 static int FNAME(walk_addr_generic)(struct guest_walker *walker,
279 struct kvm_vcpu *vcpu, struct kvm_mmu *mmu,
280 gva_t addr, u32 access)
281 {
282 int ret;
283 pt_element_t pte;
284 pt_element_t __user *uninitialized_var(ptep_user);
285 gfn_t table_gfn;
286 u64 pt_access, pte_access;
287 unsigned index, accessed_dirty, pte_pkey;
288 unsigned nested_access;
289 gpa_t pte_gpa;
290 bool have_ad;
291 int offset;
292 u64 walk_nx_mask = 0;
293 const int write_fault = access & PFERR_WRITE_MASK;
294 const int user_fault = access & PFERR_USER_MASK;
295 const int fetch_fault = access & PFERR_FETCH_MASK;
296 u16 errcode = 0;
297 gpa_t real_gpa;
298 gfn_t gfn;
299
300 trace_kvm_mmu_pagetable_walk(addr, access);
301 retry_walk:
302 walker->level = mmu->root_level;
303 pte = mmu->get_cr3(vcpu);
304 have_ad = PT_HAVE_ACCESSED_DIRTY(mmu);
305
306 #if PTTYPE == 64
307 walk_nx_mask = 1ULL << PT64_NX_SHIFT;
308 if (walker->level == PT32E_ROOT_LEVEL) {
309 pte = mmu->get_pdptr(vcpu, (addr >> 30) & 3);
310 trace_kvm_mmu_paging_element(pte, walker->level);
311 if (!FNAME(is_present_gpte)(pte))
312 goto error;
313 --walker->level;
314 }
315 #endif
316 walker->max_level = walker->level;
317 ASSERT(!(is_long_mode(vcpu) && !is_pae(vcpu)));
318
319 /*
320 * FIXME: on Intel processors, loads of the PDPTE registers for PAE paging
321 * by the MOV to CR instruction are treated as reads and do not cause the
322 * processor to set the dirty flag in any EPT paging-structure entry.
323 */
324 nested_access = (have_ad ? PFERR_WRITE_MASK : 0) | PFERR_USER_MASK;
325
326 pte_access = ~0;
327 ++walker->level;
328
329 do {
330 gfn_t real_gfn;
331 unsigned long host_addr;
332
333 pt_access = pte_access;
334 --walker->level;
335
336 index = PT_INDEX(addr, walker->level);
337 table_gfn = gpte_to_gfn(pte);
338 offset = index * sizeof(pt_element_t);
339 pte_gpa = gfn_to_gpa(table_gfn) + offset;
340
341 BUG_ON(walker->level < 1);
342 walker->table_gfn[walker->level - 1] = table_gfn;
343 walker->pte_gpa[walker->level - 1] = pte_gpa;
344
345 real_gfn = mmu->translate_gpa(vcpu, gfn_to_gpa(table_gfn),
346 nested_access,
347 &walker->fault);
348
349 /*
350 * FIXME: This can happen if emulation (for of an INS/OUTS
351 * instruction) triggers a nested page fault. The exit
352 * qualification / exit info field will incorrectly have
353 * "guest page access" as the nested page fault's cause,
354 * instead of "guest page structure access". To fix this,
355 * the x86_exception struct should be augmented with enough
356 * information to fix the exit_qualification or exit_info_1
357 * fields.
358 */
359 if (unlikely(real_gfn == UNMAPPED_GVA))
360 return 0;
361
362 real_gfn = gpa_to_gfn(real_gfn);
363
364 host_addr = kvm_vcpu_gfn_to_hva_prot(vcpu, real_gfn,
365 &walker->pte_writable[walker->level - 1]);
366 if (unlikely(kvm_is_error_hva(host_addr)))
367 goto error;
368
369 ptep_user = (pt_element_t __user *)((void *)host_addr + offset);
370 if (unlikely(__copy_from_user(&pte, ptep_user, sizeof(pte))))
371 goto error;
372 walker->ptep_user[walker->level - 1] = ptep_user;
373
374 trace_kvm_mmu_paging_element(pte, walker->level);
375
376 /*
377 * Inverting the NX it lets us AND it like other
378 * permission bits.
379 */
380 pte_access = pt_access & (pte ^ walk_nx_mask);
381
382 if (unlikely(!FNAME(is_present_gpte)(pte)))
383 goto error;
384
385 if (unlikely(is_rsvd_bits_set(mmu, pte, walker->level))) {
386 errcode = PFERR_RSVD_MASK | PFERR_PRESENT_MASK;
387 goto error;
388 }
389
390 walker->ptes[walker->level - 1] = pte;
391 } while (!is_last_gpte(mmu, walker->level, pte));
392
393 pte_pkey = FNAME(gpte_pkeys)(vcpu, pte);
394 accessed_dirty = have_ad ? pte_access & PT_GUEST_ACCESSED_MASK : 0;
395
396 /* Convert to ACC_*_MASK flags for struct guest_walker. */
397 walker->pt_access = FNAME(gpte_access)(pt_access ^ walk_nx_mask);
398 walker->pte_access = FNAME(gpte_access)(pte_access ^ walk_nx_mask);
399 errcode = permission_fault(vcpu, mmu, walker->pte_access, pte_pkey, access);
400 if (unlikely(errcode))
401 goto error;
402
403 gfn = gpte_to_gfn_lvl(pte, walker->level);
404 gfn += (addr & PT_LVL_OFFSET_MASK(walker->level)) >> PAGE_SHIFT;
405
406 if (PTTYPE == 32 && walker->level == PT_DIRECTORY_LEVEL && is_cpuid_PSE36())
407 gfn += pse36_gfn_delta(pte);
408
409 real_gpa = mmu->translate_gpa(vcpu, gfn_to_gpa(gfn), access, &walker->fault);
410 if (real_gpa == UNMAPPED_GVA)
411 return 0;
412
413 walker->gfn = real_gpa >> PAGE_SHIFT;
414
415 if (!write_fault)
416 FNAME(protect_clean_gpte)(mmu, &walker->pte_access, pte);
417 else
418 /*
419 * On a write fault, fold the dirty bit into accessed_dirty.
420 * For modes without A/D bits support accessed_dirty will be
421 * always clear.
422 */
423 accessed_dirty &= pte >>
424 (PT_GUEST_DIRTY_SHIFT - PT_GUEST_ACCESSED_SHIFT);
425
426 if (unlikely(!accessed_dirty)) {
427 ret = FNAME(update_accessed_dirty_bits)(vcpu, mmu, walker, write_fault);
428 if (unlikely(ret < 0))
429 goto error;
430 else if (ret)
431 goto retry_walk;
432 }
433
434 pgprintk("%s: pte %llx pte_access %x pt_access %x\n",
435 __func__, (u64)pte, walker->pte_access, walker->pt_access);
436 return 1;
437
438 error:
439 errcode |= write_fault | user_fault;
440 if (fetch_fault && (mmu->nx ||
441 kvm_read_cr4_bits(vcpu, X86_CR4_SMEP)))
442 errcode |= PFERR_FETCH_MASK;
443
444 walker->fault.vector = PF_VECTOR;
445 walker->fault.error_code_valid = true;
446 walker->fault.error_code = errcode;
447
448 #if PTTYPE == PTTYPE_EPT
449 /*
450 * Use PFERR_RSVD_MASK in error_code to to tell if EPT
451 * misconfiguration requires to be injected. The detection is
452 * done by is_rsvd_bits_set() above.
453 *
454 * We set up the value of exit_qualification to inject:
455 * [2:0] - Derive from the access bits. The exit_qualification might be
456 * out of date if it is serving an EPT misconfiguration.
457 * [5:3] - Calculated by the page walk of the guest EPT page tables
458 * [7:8] - Derived from [7:8] of real exit_qualification
459 *
460 * The other bits are set to 0.
461 */
462 if (!(errcode & PFERR_RSVD_MASK)) {
463 vcpu->arch.exit_qualification &= 0x180;
464 if (write_fault)
465 vcpu->arch.exit_qualification |= EPT_VIOLATION_ACC_WRITE;
466 if (user_fault)
467 vcpu->arch.exit_qualification |= EPT_VIOLATION_ACC_READ;
468 if (fetch_fault)
469 vcpu->arch.exit_qualification |= EPT_VIOLATION_ACC_INSTR;
470 vcpu->arch.exit_qualification |= (pte_access & 0x7) << 3;
471 }
472 #endif
473 walker->fault.address = addr;
474 walker->fault.nested_page_fault = mmu != vcpu->arch.walk_mmu;
475
476 trace_kvm_mmu_walker_error(walker->fault.error_code);
477 return 0;
478 }
479
FNAME(walk_addr)480 static int FNAME(walk_addr)(struct guest_walker *walker,
481 struct kvm_vcpu *vcpu, gva_t addr, u32 access)
482 {
483 return FNAME(walk_addr_generic)(walker, vcpu, &vcpu->arch.mmu, addr,
484 access);
485 }
486
487 #if PTTYPE != PTTYPE_EPT
FNAME(walk_addr_nested)488 static int FNAME(walk_addr_nested)(struct guest_walker *walker,
489 struct kvm_vcpu *vcpu, gva_t addr,
490 u32 access)
491 {
492 return FNAME(walk_addr_generic)(walker, vcpu, &vcpu->arch.nested_mmu,
493 addr, access);
494 }
495 #endif
496
497 static bool
FNAME(prefetch_gpte)498 FNAME(prefetch_gpte)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp,
499 u64 *spte, pt_element_t gpte, bool no_dirty_log)
500 {
501 unsigned pte_access;
502 gfn_t gfn;
503 kvm_pfn_t pfn;
504
505 if (FNAME(prefetch_invalid_gpte)(vcpu, sp, spte, gpte))
506 return false;
507
508 pgprintk("%s: gpte %llx spte %p\n", __func__, (u64)gpte, spte);
509
510 gfn = gpte_to_gfn(gpte);
511 pte_access = sp->role.access & FNAME(gpte_access)(gpte);
512 FNAME(protect_clean_gpte)(&vcpu->arch.mmu, &pte_access, gpte);
513 pfn = pte_prefetch_gfn_to_pfn(vcpu, gfn,
514 no_dirty_log && (pte_access & ACC_WRITE_MASK));
515 if (is_error_pfn(pfn))
516 return false;
517
518 /*
519 * we call mmu_set_spte() with host_writable = true because
520 * pte_prefetch_gfn_to_pfn always gets a writable pfn.
521 */
522 mmu_set_spte(vcpu, spte, pte_access, 0, PT_PAGE_TABLE_LEVEL, gfn, pfn,
523 true, true);
524
525 return true;
526 }
527
FNAME(update_pte)528 static void FNAME(update_pte)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp,
529 u64 *spte, const void *pte)
530 {
531 pt_element_t gpte = *(const pt_element_t *)pte;
532
533 FNAME(prefetch_gpte)(vcpu, sp, spte, gpte, false);
534 }
535
FNAME(gpte_changed)536 static bool FNAME(gpte_changed)(struct kvm_vcpu *vcpu,
537 struct guest_walker *gw, int level)
538 {
539 pt_element_t curr_pte;
540 gpa_t base_gpa, pte_gpa = gw->pte_gpa[level - 1];
541 u64 mask;
542 int r, index;
543
544 if (level == PT_PAGE_TABLE_LEVEL) {
545 mask = PTE_PREFETCH_NUM * sizeof(pt_element_t) - 1;
546 base_gpa = pte_gpa & ~mask;
547 index = (pte_gpa - base_gpa) / sizeof(pt_element_t);
548
549 r = kvm_vcpu_read_guest_atomic(vcpu, base_gpa,
550 gw->prefetch_ptes, sizeof(gw->prefetch_ptes));
551 curr_pte = gw->prefetch_ptes[index];
552 } else
553 r = kvm_vcpu_read_guest_atomic(vcpu, pte_gpa,
554 &curr_pte, sizeof(curr_pte));
555
556 return r || curr_pte != gw->ptes[level - 1];
557 }
558
FNAME(pte_prefetch)559 static void FNAME(pte_prefetch)(struct kvm_vcpu *vcpu, struct guest_walker *gw,
560 u64 *sptep)
561 {
562 struct kvm_mmu_page *sp;
563 pt_element_t *gptep = gw->prefetch_ptes;
564 u64 *spte;
565 int i;
566
567 sp = page_header(__pa(sptep));
568
569 if (sp->role.level > PT_PAGE_TABLE_LEVEL)
570 return;
571
572 if (sp->role.direct)
573 return __direct_pte_prefetch(vcpu, sp, sptep);
574
575 i = (sptep - sp->spt) & ~(PTE_PREFETCH_NUM - 1);
576 spte = sp->spt + i;
577
578 for (i = 0; i < PTE_PREFETCH_NUM; i++, spte++) {
579 if (spte == sptep)
580 continue;
581
582 if (is_shadow_present_pte(*spte))
583 continue;
584
585 if (!FNAME(prefetch_gpte)(vcpu, sp, spte, gptep[i], true))
586 break;
587 }
588 }
589
590 /*
591 * Fetch a shadow pte for a specific level in the paging hierarchy.
592 * If the guest tries to write a write-protected page, we need to
593 * emulate this operation, return 1 to indicate this case.
594 */
FNAME(fetch)595 static int FNAME(fetch)(struct kvm_vcpu *vcpu, gva_t addr,
596 struct guest_walker *gw,
597 int write_fault, int hlevel,
598 kvm_pfn_t pfn, bool map_writable, bool prefault)
599 {
600 struct kvm_mmu_page *sp = NULL;
601 struct kvm_shadow_walk_iterator it;
602 unsigned direct_access, access = gw->pt_access;
603 int top_level, ret;
604
605 direct_access = gw->pte_access;
606
607 top_level = vcpu->arch.mmu.root_level;
608 if (top_level == PT32E_ROOT_LEVEL)
609 top_level = PT32_ROOT_LEVEL;
610 /*
611 * Verify that the top-level gpte is still there. Since the page
612 * is a root page, it is either write protected (and cannot be
613 * changed from now on) or it is invalid (in which case, we don't
614 * really care if it changes underneath us after this point).
615 */
616 if (FNAME(gpte_changed)(vcpu, gw, top_level))
617 goto out_gpte_changed;
618
619 if (!VALID_PAGE(vcpu->arch.mmu.root_hpa))
620 goto out_gpte_changed;
621
622 for (shadow_walk_init(&it, vcpu, addr);
623 shadow_walk_okay(&it) && it.level > gw->level;
624 shadow_walk_next(&it)) {
625 gfn_t table_gfn;
626
627 clear_sp_write_flooding_count(it.sptep);
628 drop_large_spte(vcpu, it.sptep);
629
630 sp = NULL;
631 if (!is_shadow_present_pte(*it.sptep)) {
632 table_gfn = gw->table_gfn[it.level - 2];
633 sp = kvm_mmu_get_page(vcpu, table_gfn, addr, it.level-1,
634 false, access);
635 }
636
637 /*
638 * Verify that the gpte in the page we've just write
639 * protected is still there.
640 */
641 if (FNAME(gpte_changed)(vcpu, gw, it.level - 1))
642 goto out_gpte_changed;
643
644 if (sp)
645 link_shadow_page(vcpu, it.sptep, sp);
646 }
647
648 for (;
649 shadow_walk_okay(&it) && it.level > hlevel;
650 shadow_walk_next(&it)) {
651 gfn_t direct_gfn;
652
653 clear_sp_write_flooding_count(it.sptep);
654 validate_direct_spte(vcpu, it.sptep, direct_access);
655
656 drop_large_spte(vcpu, it.sptep);
657
658 if (is_shadow_present_pte(*it.sptep))
659 continue;
660
661 direct_gfn = gw->gfn & ~(KVM_PAGES_PER_HPAGE(it.level) - 1);
662
663 sp = kvm_mmu_get_page(vcpu, direct_gfn, addr, it.level-1,
664 true, direct_access);
665 link_shadow_page(vcpu, it.sptep, sp);
666 }
667
668 clear_sp_write_flooding_count(it.sptep);
669 ret = mmu_set_spte(vcpu, it.sptep, gw->pte_access, write_fault,
670 it.level, gw->gfn, pfn, prefault, map_writable);
671 FNAME(pte_prefetch)(vcpu, gw, it.sptep);
672
673 return ret;
674
675 out_gpte_changed:
676 kvm_release_pfn_clean(pfn);
677 return RET_PF_RETRY;
678 }
679
680 /*
681 * To see whether the mapped gfn can write its page table in the current
682 * mapping.
683 *
684 * It is the helper function of FNAME(page_fault). When guest uses large page
685 * size to map the writable gfn which is used as current page table, we should
686 * force kvm to use small page size to map it because new shadow page will be
687 * created when kvm establishes shadow page table that stop kvm using large
688 * page size. Do it early can avoid unnecessary #PF and emulation.
689 *
690 * @write_fault_to_shadow_pgtable will return true if the fault gfn is
691 * currently used as its page table.
692 *
693 * Note: the PDPT page table is not checked for PAE-32 bit guest. It is ok
694 * since the PDPT is always shadowed, that means, we can not use large page
695 * size to map the gfn which is used as PDPT.
696 */
697 static bool
FNAME(is_self_change_mapping)698 FNAME(is_self_change_mapping)(struct kvm_vcpu *vcpu,
699 struct guest_walker *walker, int user_fault,
700 bool *write_fault_to_shadow_pgtable)
701 {
702 int level;
703 gfn_t mask = ~(KVM_PAGES_PER_HPAGE(walker->level) - 1);
704 bool self_changed = false;
705
706 if (!(walker->pte_access & ACC_WRITE_MASK ||
707 (!is_write_protection(vcpu) && !user_fault)))
708 return false;
709
710 for (level = walker->level; level <= walker->max_level; level++) {
711 gfn_t gfn = walker->gfn ^ walker->table_gfn[level - 1];
712
713 self_changed |= !(gfn & mask);
714 *write_fault_to_shadow_pgtable |= !gfn;
715 }
716
717 return self_changed;
718 }
719
720 /*
721 * Page fault handler. There are several causes for a page fault:
722 * - there is no shadow pte for the guest pte
723 * - write access through a shadow pte marked read only so that we can set
724 * the dirty bit
725 * - write access to a shadow pte marked read only so we can update the page
726 * dirty bitmap, when userspace requests it
727 * - mmio access; in this case we will never install a present shadow pte
728 * - normal guest page fault due to the guest pte marked not present, not
729 * writable, or not executable
730 *
731 * Returns: 1 if we need to emulate the instruction, 0 otherwise, or
732 * a negative value on error.
733 */
FNAME(page_fault)734 static int FNAME(page_fault)(struct kvm_vcpu *vcpu, gva_t addr, u32 error_code,
735 bool prefault)
736 {
737 int write_fault = error_code & PFERR_WRITE_MASK;
738 int user_fault = error_code & PFERR_USER_MASK;
739 struct guest_walker walker;
740 int r;
741 kvm_pfn_t pfn;
742 int level = PT_PAGE_TABLE_LEVEL;
743 bool force_pt_level = false;
744 unsigned long mmu_seq;
745 bool map_writable, is_self_change_mapping;
746
747 pgprintk("%s: addr %lx err %x\n", __func__, addr, error_code);
748
749 r = mmu_topup_memory_caches(vcpu);
750 if (r)
751 return r;
752
753 /*
754 * If PFEC.RSVD is set, this is a shadow page fault.
755 * The bit needs to be cleared before walking guest page tables.
756 */
757 error_code &= ~PFERR_RSVD_MASK;
758
759 /*
760 * Look up the guest pte for the faulting address.
761 */
762 r = FNAME(walk_addr)(&walker, vcpu, addr, error_code);
763
764 /*
765 * The page is not mapped by the guest. Let the guest handle it.
766 */
767 if (!r) {
768 pgprintk("%s: guest page fault\n", __func__);
769 if (!prefault)
770 inject_page_fault(vcpu, &walker.fault);
771
772 return RET_PF_RETRY;
773 }
774
775 if (page_fault_handle_page_track(vcpu, error_code, walker.gfn)) {
776 shadow_page_table_clear_flood(vcpu, addr);
777 return RET_PF_EMULATE;
778 }
779
780 vcpu->arch.write_fault_to_shadow_pgtable = false;
781
782 is_self_change_mapping = FNAME(is_self_change_mapping)(vcpu,
783 &walker, user_fault, &vcpu->arch.write_fault_to_shadow_pgtable);
784
785 if (walker.level >= PT_DIRECTORY_LEVEL && !is_self_change_mapping) {
786 level = mapping_level(vcpu, walker.gfn, &force_pt_level);
787 if (likely(!force_pt_level)) {
788 level = min(walker.level, level);
789 walker.gfn = walker.gfn & ~(KVM_PAGES_PER_HPAGE(level) - 1);
790 }
791 } else
792 force_pt_level = true;
793
794 mmu_seq = vcpu->kvm->mmu_notifier_seq;
795 smp_rmb();
796
797 if (try_async_pf(vcpu, prefault, walker.gfn, addr, &pfn, write_fault,
798 &map_writable))
799 return RET_PF_RETRY;
800
801 if (handle_abnormal_pfn(vcpu, addr, walker.gfn, pfn, walker.pte_access, &r))
802 return r;
803
804 /*
805 * Do not change pte_access if the pfn is a mmio page, otherwise
806 * we will cache the incorrect access into mmio spte.
807 */
808 if (write_fault && !(walker.pte_access & ACC_WRITE_MASK) &&
809 !is_write_protection(vcpu) && !user_fault &&
810 !is_noslot_pfn(pfn)) {
811 walker.pte_access |= ACC_WRITE_MASK;
812 walker.pte_access &= ~ACC_USER_MASK;
813
814 /*
815 * If we converted a user page to a kernel page,
816 * so that the kernel can write to it when cr0.wp=0,
817 * then we should prevent the kernel from executing it
818 * if SMEP is enabled.
819 */
820 if (kvm_read_cr4_bits(vcpu, X86_CR4_SMEP))
821 walker.pte_access &= ~ACC_EXEC_MASK;
822 }
823
824 spin_lock(&vcpu->kvm->mmu_lock);
825 if (mmu_notifier_retry(vcpu->kvm, mmu_seq))
826 goto out_unlock;
827
828 kvm_mmu_audit(vcpu, AUDIT_PRE_PAGE_FAULT);
829 if (make_mmu_pages_available(vcpu) < 0)
830 goto out_unlock;
831 if (!force_pt_level)
832 transparent_hugepage_adjust(vcpu, &walker.gfn, &pfn, &level);
833 r = FNAME(fetch)(vcpu, addr, &walker, write_fault,
834 level, pfn, map_writable, prefault);
835 ++vcpu->stat.pf_fixed;
836 kvm_mmu_audit(vcpu, AUDIT_POST_PAGE_FAULT);
837 spin_unlock(&vcpu->kvm->mmu_lock);
838
839 return r;
840
841 out_unlock:
842 spin_unlock(&vcpu->kvm->mmu_lock);
843 kvm_release_pfn_clean(pfn);
844 return RET_PF_RETRY;
845 }
846
FNAME(get_level1_sp_gpa)847 static gpa_t FNAME(get_level1_sp_gpa)(struct kvm_mmu_page *sp)
848 {
849 int offset = 0;
850
851 WARN_ON(sp->role.level != PT_PAGE_TABLE_LEVEL);
852
853 if (PTTYPE == 32)
854 offset = sp->role.quadrant << PT64_LEVEL_BITS;
855
856 return gfn_to_gpa(sp->gfn) + offset * sizeof(pt_element_t);
857 }
858
FNAME(invlpg)859 static void FNAME(invlpg)(struct kvm_vcpu *vcpu, gva_t gva, hpa_t root_hpa)
860 {
861 struct kvm_shadow_walk_iterator iterator;
862 struct kvm_mmu_page *sp;
863 int level;
864 u64 *sptep;
865
866 vcpu_clear_mmio_info(vcpu, gva);
867
868 /*
869 * No need to check return value here, rmap_can_add() can
870 * help us to skip pte prefetch later.
871 */
872 mmu_topup_memory_caches(vcpu);
873
874 if (!VALID_PAGE(root_hpa)) {
875 WARN_ON(1);
876 return;
877 }
878
879 spin_lock(&vcpu->kvm->mmu_lock);
880 for_each_shadow_entry_using_root(vcpu, root_hpa, gva, iterator) {
881 level = iterator.level;
882 sptep = iterator.sptep;
883
884 sp = page_header(__pa(sptep));
885 if (is_last_spte(*sptep, level)) {
886 pt_element_t gpte;
887 gpa_t pte_gpa;
888
889 if (!sp->unsync)
890 break;
891
892 pte_gpa = FNAME(get_level1_sp_gpa)(sp);
893 pte_gpa += (sptep - sp->spt) * sizeof(pt_element_t);
894
895 if (mmu_page_zap_pte(vcpu->kvm, sp, sptep))
896 kvm_flush_remote_tlbs(vcpu->kvm);
897
898 if (!rmap_can_add(vcpu))
899 break;
900
901 if (kvm_vcpu_read_guest_atomic(vcpu, pte_gpa, &gpte,
902 sizeof(pt_element_t)))
903 break;
904
905 FNAME(update_pte)(vcpu, sp, sptep, &gpte);
906 }
907
908 if (!is_shadow_present_pte(*sptep) || !sp->unsync_children)
909 break;
910 }
911 spin_unlock(&vcpu->kvm->mmu_lock);
912 }
913
FNAME(gva_to_gpa)914 static gpa_t FNAME(gva_to_gpa)(struct kvm_vcpu *vcpu, gva_t vaddr, u32 access,
915 struct x86_exception *exception)
916 {
917 struct guest_walker walker;
918 gpa_t gpa = UNMAPPED_GVA;
919 int r;
920
921 r = FNAME(walk_addr)(&walker, vcpu, vaddr, access);
922
923 if (r) {
924 gpa = gfn_to_gpa(walker.gfn);
925 gpa |= vaddr & ~PAGE_MASK;
926 } else if (exception)
927 *exception = walker.fault;
928
929 return gpa;
930 }
931
932 #if PTTYPE != PTTYPE_EPT
FNAME(gva_to_gpa_nested)933 static gpa_t FNAME(gva_to_gpa_nested)(struct kvm_vcpu *vcpu, gva_t vaddr,
934 u32 access,
935 struct x86_exception *exception)
936 {
937 struct guest_walker walker;
938 gpa_t gpa = UNMAPPED_GVA;
939 int r;
940
941 r = FNAME(walk_addr_nested)(&walker, vcpu, vaddr, access);
942
943 if (r) {
944 gpa = gfn_to_gpa(walker.gfn);
945 gpa |= vaddr & ~PAGE_MASK;
946 } else if (exception)
947 *exception = walker.fault;
948
949 return gpa;
950 }
951 #endif
952
953 /*
954 * Using the cached information from sp->gfns is safe because:
955 * - The spte has a reference to the struct page, so the pfn for a given gfn
956 * can't change unless all sptes pointing to it are nuked first.
957 *
958 * Note:
959 * We should flush all tlbs if spte is dropped even though guest is
960 * responsible for it. Since if we don't, kvm_mmu_notifier_invalidate_page
961 * and kvm_mmu_notifier_invalidate_range_start detect the mapping page isn't
962 * used by guest then tlbs are not flushed, so guest is allowed to access the
963 * freed pages.
964 * And we increase kvm->tlbs_dirty to delay tlbs flush in this case.
965 */
FNAME(sync_page)966 static int FNAME(sync_page)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp)
967 {
968 int i, nr_present = 0;
969 bool host_writable;
970 gpa_t first_pte_gpa;
971 int set_spte_ret = 0;
972
973 /* direct kvm_mmu_page can not be unsync. */
974 BUG_ON(sp->role.direct);
975
976 first_pte_gpa = FNAME(get_level1_sp_gpa)(sp);
977
978 for (i = 0; i < PT64_ENT_PER_PAGE; i++) {
979 unsigned pte_access;
980 pt_element_t gpte;
981 gpa_t pte_gpa;
982 gfn_t gfn;
983
984 if (!sp->spt[i])
985 continue;
986
987 pte_gpa = first_pte_gpa + i * sizeof(pt_element_t);
988
989 if (kvm_vcpu_read_guest_atomic(vcpu, pte_gpa, &gpte,
990 sizeof(pt_element_t)))
991 return 0;
992
993 if (FNAME(prefetch_invalid_gpte)(vcpu, sp, &sp->spt[i], gpte)) {
994 /*
995 * Update spte before increasing tlbs_dirty to make
996 * sure no tlb flush is lost after spte is zapped; see
997 * the comments in kvm_flush_remote_tlbs().
998 */
999 smp_wmb();
1000 vcpu->kvm->tlbs_dirty++;
1001 continue;
1002 }
1003
1004 gfn = gpte_to_gfn(gpte);
1005 pte_access = sp->role.access;
1006 pte_access &= FNAME(gpte_access)(gpte);
1007 FNAME(protect_clean_gpte)(&vcpu->arch.mmu, &pte_access, gpte);
1008
1009 if (sync_mmio_spte(vcpu, &sp->spt[i], gfn, pte_access,
1010 &nr_present))
1011 continue;
1012
1013 if (gfn != sp->gfns[i]) {
1014 drop_spte(vcpu->kvm, &sp->spt[i]);
1015 /*
1016 * The same as above where we are doing
1017 * prefetch_invalid_gpte().
1018 */
1019 smp_wmb();
1020 vcpu->kvm->tlbs_dirty++;
1021 continue;
1022 }
1023
1024 nr_present++;
1025
1026 host_writable = sp->spt[i] & SPTE_HOST_WRITEABLE;
1027
1028 set_spte_ret |= set_spte(vcpu, &sp->spt[i],
1029 pte_access, PT_PAGE_TABLE_LEVEL,
1030 gfn, spte_to_pfn(sp->spt[i]),
1031 true, false, host_writable);
1032 }
1033
1034 if (set_spte_ret & SET_SPTE_NEED_REMOTE_TLB_FLUSH)
1035 kvm_flush_remote_tlbs(vcpu->kvm);
1036
1037 return nr_present;
1038 }
1039
1040 #undef pt_element_t
1041 #undef guest_walker
1042 #undef FNAME
1043 #undef PT_BASE_ADDR_MASK
1044 #undef PT_INDEX
1045 #undef PT_LVL_ADDR_MASK
1046 #undef PT_LVL_OFFSET_MASK
1047 #undef PT_LEVEL_BITS
1048 #undef PT_MAX_FULL_LEVELS
1049 #undef gpte_to_gfn
1050 #undef gpte_to_gfn_lvl
1051 #undef CMPXCHG
1052 #undef PT_GUEST_ACCESSED_MASK
1053 #undef PT_GUEST_DIRTY_MASK
1054 #undef PT_GUEST_DIRTY_SHIFT
1055 #undef PT_GUEST_ACCESSED_SHIFT
1056 #undef PT_HAVE_ACCESSED_DIRTY
1057
