xref: /linux/arch/x86/kvm/mmu/spte.h (revision f4738f56d1dc62aaba69b33702a5ab098f1b8c63)
1 // SPDX-License-Identifier: GPL-2.0-only
2 
3 #ifndef KVM_X86_MMU_SPTE_H
4 #define KVM_X86_MMU_SPTE_H
5 
6 #include "mmu.h"
7 #include "mmu_internal.h"
8 
9 /*
10  * A MMU present SPTE is backed by actual memory and may or may not be present
11  * in hardware.  E.g. MMIO SPTEs are not considered present.  Use bit 11, as it
12  * is ignored by all flavors of SPTEs and checking a low bit often generates
13  * better code than for a high bit, e.g. 56+.  MMU present checks are pervasive
14  * enough that the improved code generation is noticeable in KVM's footprint.
15  */
16 #define SPTE_MMU_PRESENT_MASK		BIT_ULL(11)
17 
18 /*
19  * TDP SPTES (more specifically, EPT SPTEs) may not have A/D bits, and may also
20  * be restricted to using write-protection (for L2 when CPU dirty logging, i.e.
21  * PML, is enabled).  Use bits 52 and 53 to hold the type of A/D tracking that
22  * is must be employed for a given TDP SPTE.
23  *
24  * Note, the "enabled" mask must be '0', as bits 62:52 are _reserved_ for PAE
25  * paging, including NPT PAE.  This scheme works because legacy shadow paging
26  * is guaranteed to have A/D bits and write-protection is forced only for
27  * TDP with CPU dirty logging (PML).  If NPT ever gains PML-like support, it
28  * must be restricted to 64-bit KVM.
29  */
30 #define SPTE_TDP_AD_SHIFT		52
31 #define SPTE_TDP_AD_MASK		(3ULL << SPTE_TDP_AD_SHIFT)
32 #define SPTE_TDP_AD_ENABLED		(0ULL << SPTE_TDP_AD_SHIFT)
33 #define SPTE_TDP_AD_DISABLED		(1ULL << SPTE_TDP_AD_SHIFT)
34 #define SPTE_TDP_AD_WRPROT_ONLY		(2ULL << SPTE_TDP_AD_SHIFT)
35 static_assert(SPTE_TDP_AD_ENABLED == 0);
36 
37 #ifdef CONFIG_DYNAMIC_PHYSICAL_MASK
38 #define SPTE_BASE_ADDR_MASK (physical_mask & ~(u64)(PAGE_SIZE-1))
39 #else
40 #define SPTE_BASE_ADDR_MASK (((1ULL << 52) - 1) & ~(u64)(PAGE_SIZE-1))
41 #endif
42 
43 #define SPTE_PERM_MASK (PT_PRESENT_MASK | PT_WRITABLE_MASK | shadow_user_mask \
44 			| shadow_x_mask | shadow_nx_mask | shadow_me_mask)
45 
46 #define ACC_EXEC_MASK    1
47 #define ACC_WRITE_MASK   PT_WRITABLE_MASK
48 #define ACC_USER_MASK    PT_USER_MASK
49 #define ACC_ALL          (ACC_EXEC_MASK | ACC_WRITE_MASK | ACC_USER_MASK)
50 
51 /* The mask for the R/X bits in EPT PTEs */
52 #define SPTE_EPT_READABLE_MASK			0x1ull
53 #define SPTE_EPT_EXECUTABLE_MASK		0x4ull
54 
55 #define SPTE_LEVEL_BITS			9
56 #define SPTE_LEVEL_SHIFT(level)		__PT_LEVEL_SHIFT(level, SPTE_LEVEL_BITS)
57 #define SPTE_INDEX(address, level)	__PT_INDEX(address, level, SPTE_LEVEL_BITS)
58 #define SPTE_ENT_PER_PAGE		__PT_ENT_PER_PAGE(SPTE_LEVEL_BITS)
59 
60 /*
61  * The mask/shift to use for saving the original R/X bits when marking the PTE
62  * as not-present for access tracking purposes. We do not save the W bit as the
63  * PTEs being access tracked also need to be dirty tracked, so the W bit will be
64  * restored only when a write is attempted to the page.  This mask obviously
65  * must not overlap the A/D type mask.
66  */
67 #define SHADOW_ACC_TRACK_SAVED_BITS_MASK (SPTE_EPT_READABLE_MASK | \
68 					  SPTE_EPT_EXECUTABLE_MASK)
69 #define SHADOW_ACC_TRACK_SAVED_BITS_SHIFT 54
70 #define SHADOW_ACC_TRACK_SAVED_MASK	(SHADOW_ACC_TRACK_SAVED_BITS_MASK << \
71 					 SHADOW_ACC_TRACK_SAVED_BITS_SHIFT)
72 static_assert(!(SPTE_TDP_AD_MASK & SHADOW_ACC_TRACK_SAVED_MASK));
73 
74 /*
75  * {DEFAULT,EPT}_SPTE_{HOST,MMU}_WRITABLE are used to keep track of why a given
76  * SPTE is write-protected. See is_writable_pte() for details.
77  */
78 
79 /* Bits 9 and 10 are ignored by all non-EPT PTEs. */
80 #define DEFAULT_SPTE_HOST_WRITABLE	BIT_ULL(9)
81 #define DEFAULT_SPTE_MMU_WRITABLE	BIT_ULL(10)
82 
83 /*
84  * Low ignored bits are at a premium for EPT, use high ignored bits, taking care
85  * to not overlap the A/D type mask or the saved access bits of access-tracked
86  * SPTEs when A/D bits are disabled.
87  */
88 #define EPT_SPTE_HOST_WRITABLE		BIT_ULL(57)
89 #define EPT_SPTE_MMU_WRITABLE		BIT_ULL(58)
90 
91 static_assert(!(EPT_SPTE_HOST_WRITABLE & SPTE_TDP_AD_MASK));
92 static_assert(!(EPT_SPTE_MMU_WRITABLE & SPTE_TDP_AD_MASK));
93 static_assert(!(EPT_SPTE_HOST_WRITABLE & SHADOW_ACC_TRACK_SAVED_MASK));
94 static_assert(!(EPT_SPTE_MMU_WRITABLE & SHADOW_ACC_TRACK_SAVED_MASK));
95 
96 /* Defined only to keep the above static asserts readable. */
97 #undef SHADOW_ACC_TRACK_SAVED_MASK
98 
99 /*
100  * Due to limited space in PTEs, the MMIO generation is a 19 bit subset of
101  * the memslots generation and is derived as follows:
102  *
103  * Bits 0-7 of the MMIO generation are propagated to spte bits 3-10
104  * Bits 8-18 of the MMIO generation are propagated to spte bits 52-62
105  *
106  * The KVM_MEMSLOT_GEN_UPDATE_IN_PROGRESS flag is intentionally not included in
107  * the MMIO generation number, as doing so would require stealing a bit from
108  * the "real" generation number and thus effectively halve the maximum number
109  * of MMIO generations that can be handled before encountering a wrap (which
110  * requires a full MMU zap).  The flag is instead explicitly queried when
111  * checking for MMIO spte cache hits.
112  */
113 
114 #define MMIO_SPTE_GEN_LOW_START		3
115 #define MMIO_SPTE_GEN_LOW_END		10
116 
117 #define MMIO_SPTE_GEN_HIGH_START	52
118 #define MMIO_SPTE_GEN_HIGH_END		62
119 
120 #define MMIO_SPTE_GEN_LOW_MASK		GENMASK_ULL(MMIO_SPTE_GEN_LOW_END, \
121 						    MMIO_SPTE_GEN_LOW_START)
122 #define MMIO_SPTE_GEN_HIGH_MASK		GENMASK_ULL(MMIO_SPTE_GEN_HIGH_END, \
123 						    MMIO_SPTE_GEN_HIGH_START)
124 static_assert(!(SPTE_MMU_PRESENT_MASK &
125 		(MMIO_SPTE_GEN_LOW_MASK | MMIO_SPTE_GEN_HIGH_MASK)));
126 
127 /*
128  * The SPTE MMIO mask must NOT overlap the MMIO generation bits or the
129  * MMU-present bit.  The generation obviously co-exists with the magic MMIO
130  * mask/value, and MMIO SPTEs are considered !MMU-present.
131  *
132  * The SPTE MMIO mask is allowed to use hardware "present" bits (i.e. all EPT
133  * RWX bits), all physical address bits (legal PA bits are used for "fast" MMIO
134  * and so they're off-limits for generation; additional checks ensure the mask
135  * doesn't overlap legal PA bits), and bit 63 (carved out for future usage).
136  */
137 #define SPTE_MMIO_ALLOWED_MASK (BIT_ULL(63) | GENMASK_ULL(51, 12) | GENMASK_ULL(2, 0))
138 static_assert(!(SPTE_MMIO_ALLOWED_MASK &
139 		(SPTE_MMU_PRESENT_MASK | MMIO_SPTE_GEN_LOW_MASK | MMIO_SPTE_GEN_HIGH_MASK)));
140 
141 #define MMIO_SPTE_GEN_LOW_BITS		(MMIO_SPTE_GEN_LOW_END - MMIO_SPTE_GEN_LOW_START + 1)
142 #define MMIO_SPTE_GEN_HIGH_BITS		(MMIO_SPTE_GEN_HIGH_END - MMIO_SPTE_GEN_HIGH_START + 1)
143 
144 /* remember to adjust the comment above as well if you change these */
145 static_assert(MMIO_SPTE_GEN_LOW_BITS == 8 && MMIO_SPTE_GEN_HIGH_BITS == 11);
146 
147 #define MMIO_SPTE_GEN_LOW_SHIFT		(MMIO_SPTE_GEN_LOW_START - 0)
148 #define MMIO_SPTE_GEN_HIGH_SHIFT	(MMIO_SPTE_GEN_HIGH_START - MMIO_SPTE_GEN_LOW_BITS)
149 
150 #define MMIO_SPTE_GEN_MASK		GENMASK_ULL(MMIO_SPTE_GEN_LOW_BITS + MMIO_SPTE_GEN_HIGH_BITS - 1, 0)
151 
152 extern u64 __read_mostly shadow_host_writable_mask;
153 extern u64 __read_mostly shadow_mmu_writable_mask;
154 extern u64 __read_mostly shadow_nx_mask;
155 extern u64 __read_mostly shadow_x_mask; /* mutual exclusive with nx_mask */
156 extern u64 __read_mostly shadow_user_mask;
157 extern u64 __read_mostly shadow_accessed_mask;
158 extern u64 __read_mostly shadow_dirty_mask;
159 extern u64 __read_mostly shadow_mmio_value;
160 extern u64 __read_mostly shadow_mmio_mask;
161 extern u64 __read_mostly shadow_mmio_access_mask;
162 extern u64 __read_mostly shadow_present_mask;
163 extern u64 __read_mostly shadow_memtype_mask;
164 extern u64 __read_mostly shadow_me_value;
165 extern u64 __read_mostly shadow_me_mask;
166 
167 /*
168  * SPTEs in MMUs without A/D bits are marked with SPTE_TDP_AD_DISABLED;
169  * shadow_acc_track_mask is the set of bits to be cleared in non-accessed
170  * pages.
171  */
172 extern u64 __read_mostly shadow_acc_track_mask;
173 
174 /*
175  * This mask must be set on all non-zero Non-Present or Reserved SPTEs in order
176  * to guard against L1TF attacks.
177  */
178 extern u64 __read_mostly shadow_nonpresent_or_rsvd_mask;
179 
180 /*
181  * The number of high-order 1 bits to use in the mask above.
182  */
183 #define SHADOW_NONPRESENT_OR_RSVD_MASK_LEN 5
184 
185 /*
186  * If a thread running without exclusive control of the MMU lock must perform a
187  * multi-part operation on an SPTE, it can set the SPTE to REMOVED_SPTE as a
188  * non-present intermediate value. Other threads which encounter this value
189  * should not modify the SPTE.
190  *
191  * Use a semi-arbitrary value that doesn't set RWX bits, i.e. is not-present on
192  * both AMD and Intel CPUs, and doesn't set PFN bits, i.e. doesn't create a L1TF
193  * vulnerability.  Use only low bits to avoid 64-bit immediates.
194  *
195  * Only used by the TDP MMU.
196  */
197 #define REMOVED_SPTE	0x5a0ULL
198 
199 /* Removed SPTEs must not be misconstrued as shadow present PTEs. */
200 static_assert(!(REMOVED_SPTE & SPTE_MMU_PRESENT_MASK));
201 
202 static inline bool is_removed_spte(u64 spte)
203 {
204 	return spte == REMOVED_SPTE;
205 }
206 
207 /* Get an SPTE's index into its parent's page table (and the spt array). */
208 static inline int spte_index(u64 *sptep)
209 {
210 	return ((unsigned long)sptep / sizeof(*sptep)) & (SPTE_ENT_PER_PAGE - 1);
211 }
212 
213 /*
214  * In some cases, we need to preserve the GFN of a non-present or reserved
215  * SPTE when we usurp the upper five bits of the physical address space to
216  * defend against L1TF, e.g. for MMIO SPTEs.  To preserve the GFN, we'll
217  * shift bits of the GFN that overlap with shadow_nonpresent_or_rsvd_mask
218  * left into the reserved bits, i.e. the GFN in the SPTE will be split into
219  * high and low parts.  This mask covers the lower bits of the GFN.
220  */
221 extern u64 __read_mostly shadow_nonpresent_or_rsvd_lower_gfn_mask;
222 
223 static inline struct kvm_mmu_page *to_shadow_page(hpa_t shadow_page)
224 {
225 	struct page *page = pfn_to_page((shadow_page) >> PAGE_SHIFT);
226 
227 	return (struct kvm_mmu_page *)page_private(page);
228 }
229 
230 static inline struct kvm_mmu_page *spte_to_child_sp(u64 spte)
231 {
232 	return to_shadow_page(spte & SPTE_BASE_ADDR_MASK);
233 }
234 
235 static inline struct kvm_mmu_page *sptep_to_sp(u64 *sptep)
236 {
237 	return to_shadow_page(__pa(sptep));
238 }
239 
240 static inline struct kvm_mmu_page *root_to_sp(hpa_t root)
241 {
242 	if (kvm_mmu_is_dummy_root(root))
243 		return NULL;
244 
245 	/*
246 	 * The "root" may be a special root, e.g. a PAE entry, treat it as a
247 	 * SPTE to ensure any non-PA bits are dropped.
248 	 */
249 	return spte_to_child_sp(root);
250 }
251 
252 static inline bool is_mmio_spte(u64 spte)
253 {
254 	return (spte & shadow_mmio_mask) == shadow_mmio_value &&
255 	       likely(enable_mmio_caching);
256 }
257 
258 static inline bool is_shadow_present_pte(u64 pte)
259 {
260 	return !!(pte & SPTE_MMU_PRESENT_MASK);
261 }
262 
263 /*
264  * Returns true if A/D bits are supported in hardware and are enabled by KVM.
265  * When enabled, KVM uses A/D bits for all non-nested MMUs.  Because L1 can
266  * disable A/D bits in EPTP12, SP and SPTE variants are needed to handle the
267  * scenario where KVM is using A/D bits for L1, but not L2.
268  */
269 static inline bool kvm_ad_enabled(void)
270 {
271 	return !!shadow_accessed_mask;
272 }
273 
274 static inline bool sp_ad_disabled(struct kvm_mmu_page *sp)
275 {
276 	return sp->role.ad_disabled;
277 }
278 
279 static inline bool spte_ad_enabled(u64 spte)
280 {
281 	KVM_MMU_WARN_ON(!is_shadow_present_pte(spte));
282 	return (spte & SPTE_TDP_AD_MASK) != SPTE_TDP_AD_DISABLED;
283 }
284 
285 static inline bool spte_ad_need_write_protect(u64 spte)
286 {
287 	KVM_MMU_WARN_ON(!is_shadow_present_pte(spte));
288 	/*
289 	 * This is benign for non-TDP SPTEs as SPTE_TDP_AD_ENABLED is '0',
290 	 * and non-TDP SPTEs will never set these bits.  Optimize for 64-bit
291 	 * TDP and do the A/D type check unconditionally.
292 	 */
293 	return (spte & SPTE_TDP_AD_MASK) != SPTE_TDP_AD_ENABLED;
294 }
295 
296 static inline u64 spte_shadow_accessed_mask(u64 spte)
297 {
298 	KVM_MMU_WARN_ON(!is_shadow_present_pte(spte));
299 	return spte_ad_enabled(spte) ? shadow_accessed_mask : 0;
300 }
301 
302 static inline u64 spte_shadow_dirty_mask(u64 spte)
303 {
304 	KVM_MMU_WARN_ON(!is_shadow_present_pte(spte));
305 	return spte_ad_enabled(spte) ? shadow_dirty_mask : 0;
306 }
307 
308 static inline bool is_access_track_spte(u64 spte)
309 {
310 	return !spte_ad_enabled(spte) && (spte & shadow_acc_track_mask) == 0;
311 }
312 
313 static inline bool is_large_pte(u64 pte)
314 {
315 	return pte & PT_PAGE_SIZE_MASK;
316 }
317 
318 static inline bool is_last_spte(u64 pte, int level)
319 {
320 	return (level == PG_LEVEL_4K) || is_large_pte(pte);
321 }
322 
323 static inline bool is_executable_pte(u64 spte)
324 {
325 	return (spte & (shadow_x_mask | shadow_nx_mask)) == shadow_x_mask;
326 }
327 
328 static inline kvm_pfn_t spte_to_pfn(u64 pte)
329 {
330 	return (pte & SPTE_BASE_ADDR_MASK) >> PAGE_SHIFT;
331 }
332 
333 static inline bool is_accessed_spte(u64 spte)
334 {
335 	u64 accessed_mask = spte_shadow_accessed_mask(spte);
336 
337 	return accessed_mask ? spte & accessed_mask
338 			     : !is_access_track_spte(spte);
339 }
340 
341 static inline bool is_dirty_spte(u64 spte)
342 {
343 	u64 dirty_mask = spte_shadow_dirty_mask(spte);
344 
345 	return dirty_mask ? spte & dirty_mask : spte & PT_WRITABLE_MASK;
346 }
347 
348 static inline u64 get_rsvd_bits(struct rsvd_bits_validate *rsvd_check, u64 pte,
349 				int level)
350 {
351 	int bit7 = (pte >> 7) & 1;
352 
353 	return rsvd_check->rsvd_bits_mask[bit7][level-1];
354 }
355 
356 static inline bool __is_rsvd_bits_set(struct rsvd_bits_validate *rsvd_check,
357 				      u64 pte, int level)
358 {
359 	return pte & get_rsvd_bits(rsvd_check, pte, level);
360 }
361 
362 static inline bool __is_bad_mt_xwr(struct rsvd_bits_validate *rsvd_check,
363 				   u64 pte)
364 {
365 	return rsvd_check->bad_mt_xwr & BIT_ULL(pte & 0x3f);
366 }
367 
368 static __always_inline bool is_rsvd_spte(struct rsvd_bits_validate *rsvd_check,
369 					 u64 spte, int level)
370 {
371 	return __is_bad_mt_xwr(rsvd_check, spte) ||
372 	       __is_rsvd_bits_set(rsvd_check, spte, level);
373 }
374 
375 /*
376  * A shadow-present leaf SPTE may be non-writable for 4 possible reasons:
377  *
378  *  1. To intercept writes for dirty logging. KVM write-protects huge pages
379  *     so that they can be split down into the dirty logging
380  *     granularity (4KiB) whenever the guest writes to them. KVM also
381  *     write-protects 4KiB pages so that writes can be recorded in the dirty log
382  *     (e.g. if not using PML). SPTEs are write-protected for dirty logging
383  *     during the VM-iotcls that enable dirty logging.
384  *
385  *  2. To intercept writes to guest page tables that KVM is shadowing. When a
386  *     guest writes to its page table the corresponding shadow page table will
387  *     be marked "unsync". That way KVM knows which shadow page tables need to
388  *     be updated on the next TLB flush, INVLPG, etc. and which do not.
389  *
390  *  3. To prevent guest writes to read-only memory, such as for memory in a
391  *     read-only memslot or guest memory backed by a read-only VMA. Writes to
392  *     such pages are disallowed entirely.
393  *
394  *  4. To emulate the Accessed bit for SPTEs without A/D bits.  Note, in this
395  *     case, the SPTE is access-protected, not just write-protected!
396  *
397  * For cases #1 and #4, KVM can safely make such SPTEs writable without taking
398  * mmu_lock as capturing the Accessed/Dirty state doesn't require taking it.
399  * To differentiate #1 and #4 from #2 and #3, KVM uses two software-only bits
400  * in the SPTE:
401  *
402  *  shadow_mmu_writable_mask, aka MMU-writable -
403  *    Cleared on SPTEs that KVM is currently write-protecting for shadow paging
404  *    purposes (case 2 above).
405  *
406  *  shadow_host_writable_mask, aka Host-writable -
407  *    Cleared on SPTEs that are not host-writable (case 3 above)
408  *
409  * Note, not all possible combinations of PT_WRITABLE_MASK,
410  * shadow_mmu_writable_mask, and shadow_host_writable_mask are valid. A given
411  * SPTE can be in only one of the following states, which map to the
412  * aforementioned 3 cases:
413  *
414  *   shadow_host_writable_mask | shadow_mmu_writable_mask | PT_WRITABLE_MASK
415  *   ------------------------- | ------------------------ | ----------------
416  *   1                         | 1                        | 1       (writable)
417  *   1                         | 1                        | 0       (case 1)
418  *   1                         | 0                        | 0       (case 2)
419  *   0                         | 0                        | 0       (case 3)
420  *
421  * The valid combinations of these bits are checked by
422  * check_spte_writable_invariants() whenever an SPTE is modified.
423  *
424  * Clearing the MMU-writable bit is always done under the MMU lock and always
425  * accompanied by a TLB flush before dropping the lock to avoid corrupting the
426  * shadow page tables between vCPUs. Write-protecting an SPTE for dirty logging
427  * (which does not clear the MMU-writable bit), does not flush TLBs before
428  * dropping the lock, as it only needs to synchronize guest writes with the
429  * dirty bitmap. Similarly, making the SPTE inaccessible (and non-writable) for
430  * access-tracking via the clear_young() MMU notifier also does not flush TLBs.
431  *
432  * So, there is the problem: clearing the MMU-writable bit can encounter a
433  * write-protected SPTE while CPUs still have writable mappings for that SPTE
434  * cached in their TLB. To address this, KVM always flushes TLBs when
435  * write-protecting SPTEs if the MMU-writable bit is set on the old SPTE.
436  *
437  * The Host-writable bit is not modified on present SPTEs, it is only set or
438  * cleared when an SPTE is first faulted in from non-present and then remains
439  * immutable.
440  */
441 static inline bool is_writable_pte(unsigned long pte)
442 {
443 	return pte & PT_WRITABLE_MASK;
444 }
445 
446 /* Note: spte must be a shadow-present leaf SPTE. */
447 static inline void check_spte_writable_invariants(u64 spte)
448 {
449 	if (spte & shadow_mmu_writable_mask)
450 		WARN_ONCE(!(spte & shadow_host_writable_mask),
451 			  KBUILD_MODNAME ": MMU-writable SPTE is not Host-writable: %llx",
452 			  spte);
453 	else
454 		WARN_ONCE(is_writable_pte(spte),
455 			  KBUILD_MODNAME ": Writable SPTE is not MMU-writable: %llx", spte);
456 }
457 
458 static inline bool is_mmu_writable_spte(u64 spte)
459 {
460 	return spte & shadow_mmu_writable_mask;
461 }
462 
463 static inline u64 get_mmio_spte_generation(u64 spte)
464 {
465 	u64 gen;
466 
467 	gen = (spte & MMIO_SPTE_GEN_LOW_MASK) >> MMIO_SPTE_GEN_LOW_SHIFT;
468 	gen |= (spte & MMIO_SPTE_GEN_HIGH_MASK) >> MMIO_SPTE_GEN_HIGH_SHIFT;
469 	return gen;
470 }
471 
472 bool spte_has_volatile_bits(u64 spte);
473 
474 bool make_spte(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp,
475 	       const struct kvm_memory_slot *slot,
476 	       unsigned int pte_access, gfn_t gfn, kvm_pfn_t pfn,
477 	       u64 old_spte, bool prefetch, bool can_unsync,
478 	       bool host_writable, u64 *new_spte);
479 u64 make_huge_page_split_spte(struct kvm *kvm, u64 huge_spte,
480 		      	      union kvm_mmu_page_role role, int index);
481 u64 make_nonleaf_spte(u64 *child_pt, bool ad_disabled);
482 u64 make_mmio_spte(struct kvm_vcpu *vcpu, u64 gfn, unsigned int access);
483 u64 mark_spte_for_access_track(u64 spte);
484 
485 /* Restore an acc-track PTE back to a regular PTE */
486 static inline u64 restore_acc_track_spte(u64 spte)
487 {
488 	u64 saved_bits = (spte >> SHADOW_ACC_TRACK_SAVED_BITS_SHIFT)
489 			 & SHADOW_ACC_TRACK_SAVED_BITS_MASK;
490 
491 	spte &= ~shadow_acc_track_mask;
492 	spte &= ~(SHADOW_ACC_TRACK_SAVED_BITS_MASK <<
493 		  SHADOW_ACC_TRACK_SAVED_BITS_SHIFT);
494 	spte |= saved_bits;
495 
496 	return spte;
497 }
498 
499 u64 kvm_mmu_changed_pte_notifier_make_spte(u64 old_spte, kvm_pfn_t new_pfn);
500 
501 void __init kvm_mmu_spte_module_init(void);
502 void kvm_mmu_reset_all_pte_masks(void);
503 
504 #endif
505