diff options
Diffstat (limited to 'arch/x86/kvm/mmu.c')
-rw-r--r-- | arch/x86/kvm/mmu.c | 509 |
1 files changed, 356 insertions, 153 deletions
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c index 7012de4a1fed..2fd7586aad4d 100644 --- a/arch/x86/kvm/mmu.c +++ b/arch/x86/kvm/mmu.c @@ -37,6 +37,8 @@ #include <linux/srcu.h> #include <linux/slab.h> #include <linux/uaccess.h> +#include <linux/hash.h> +#include <linux/kern_levels.h> #include <asm/page.h> #include <asm/cmpxchg.h> @@ -129,6 +131,10 @@ module_param(dbg, bool, 0644); #define ACC_USER_MASK PT_USER_MASK #define ACC_ALL (ACC_EXEC_MASK | ACC_WRITE_MASK | ACC_USER_MASK) +/* The mask for the R/X bits in EPT PTEs */ +#define PT64_EPT_READABLE_MASK 0x1ull +#define PT64_EPT_EXECUTABLE_MASK 0x4ull + #include <trace/events/kvm.h> #define CREATE_TRACE_POINTS @@ -178,15 +184,40 @@ static u64 __read_mostly shadow_dirty_mask; static u64 __read_mostly shadow_mmio_mask; static u64 __read_mostly shadow_present_mask; +/* + * The mask/value to distinguish a PTE that has been marked not-present for + * access tracking purposes. + * The mask would be either 0 if access tracking is disabled, or + * SPTE_SPECIAL_MASK|VMX_EPT_RWX_MASK if access tracking is enabled. + */ +static u64 __read_mostly shadow_acc_track_mask; +static const u64 shadow_acc_track_value = SPTE_SPECIAL_MASK; + +/* + * The mask/shift to use for saving the original R/X bits when marking the PTE + * as not-present for access tracking purposes. We do not save the W bit as the + * PTEs being access tracked also need to be dirty tracked, so the W bit will be + * restored only when a write is attempted to the page. + */ +static const u64 shadow_acc_track_saved_bits_mask = PT64_EPT_READABLE_MASK | + PT64_EPT_EXECUTABLE_MASK; +static const u64 shadow_acc_track_saved_bits_shift = PT64_SECOND_AVAIL_BITS_SHIFT; + static void mmu_spte_set(u64 *sptep, u64 spte); static void mmu_free_roots(struct kvm_vcpu *vcpu); void kvm_mmu_set_mmio_spte_mask(u64 mmio_mask) { - shadow_mmio_mask = mmio_mask; + shadow_mmio_mask = mmio_mask | SPTE_SPECIAL_MASK; } EXPORT_SYMBOL_GPL(kvm_mmu_set_mmio_spte_mask); +static inline bool is_access_track_spte(u64 spte) +{ + /* Always false if shadow_acc_track_mask is zero. */ + return (spte & shadow_acc_track_mask) == shadow_acc_track_value; +} + /* * the low bit of the generation number is always presumed to be zero. * This disables mmio caching during memslot updates. The concept is @@ -284,17 +315,35 @@ static bool check_mmio_spte(struct kvm_vcpu *vcpu, u64 spte) } void kvm_mmu_set_mask_ptes(u64 user_mask, u64 accessed_mask, - u64 dirty_mask, u64 nx_mask, u64 x_mask, u64 p_mask) + u64 dirty_mask, u64 nx_mask, u64 x_mask, u64 p_mask, + u64 acc_track_mask) { + if (acc_track_mask != 0) + acc_track_mask |= SPTE_SPECIAL_MASK; + shadow_user_mask = user_mask; shadow_accessed_mask = accessed_mask; shadow_dirty_mask = dirty_mask; shadow_nx_mask = nx_mask; shadow_x_mask = x_mask; shadow_present_mask = p_mask; + shadow_acc_track_mask = acc_track_mask; + WARN_ON(shadow_accessed_mask != 0 && shadow_acc_track_mask != 0); } EXPORT_SYMBOL_GPL(kvm_mmu_set_mask_ptes); +void kvm_mmu_clear_all_pte_masks(void) +{ + shadow_user_mask = 0; + shadow_accessed_mask = 0; + shadow_dirty_mask = 0; + shadow_nx_mask = 0; + shadow_x_mask = 0; + shadow_mmio_mask = 0; + shadow_present_mask = 0; + shadow_acc_track_mask = 0; +} + static int is_cpuid_PSE36(void) { return 1; @@ -307,7 +356,7 @@ static int is_nx(struct kvm_vcpu *vcpu) static int is_shadow_present_pte(u64 pte) { - return (pte & 0xFFFFFFFFull) && !is_mmio_spte(pte); + return (pte != 0) && !is_mmio_spte(pte); } static int is_large_pte(u64 pte) @@ -324,6 +373,11 @@ static int is_last_spte(u64 pte, int level) return 0; } +static bool is_executable_pte(u64 spte) +{ + return (spte & (shadow_x_mask | shadow_nx_mask)) == shadow_x_mask; +} + static kvm_pfn_t spte_to_pfn(u64 pte) { return (pte & PT64_BASE_ADDR_MASK) >> PAGE_SHIFT; @@ -473,7 +527,7 @@ retry: } #endif -static bool spte_is_locklessly_modifiable(u64 spte) +static bool spte_can_locklessly_be_made_writable(u64 spte) { return (spte & (SPTE_HOST_WRITEABLE | SPTE_MMU_WRITEABLE)) == (SPTE_HOST_WRITEABLE | SPTE_MMU_WRITEABLE); @@ -481,36 +535,38 @@ static bool spte_is_locklessly_modifiable(u64 spte) static bool spte_has_volatile_bits(u64 spte) { + if (!is_shadow_present_pte(spte)) + return false; + /* * Always atomically update spte if it can be updated * out of mmu-lock, it can ensure dirty bit is not lost, * also, it can help us to get a stable is_writable_pte() * to ensure tlb flush is not missed. */ - if (spte_is_locklessly_modifiable(spte)) + if (spte_can_locklessly_be_made_writable(spte) || + is_access_track_spte(spte)) return true; - if (!shadow_accessed_mask) - return false; - - if (!is_shadow_present_pte(spte)) - return false; - - if ((spte & shadow_accessed_mask) && - (!is_writable_pte(spte) || (spte & shadow_dirty_mask))) - return false; + if (shadow_accessed_mask) { + if ((spte & shadow_accessed_mask) == 0 || + (is_writable_pte(spte) && (spte & shadow_dirty_mask) == 0)) + return true; + } - return true; + return false; } -static bool spte_is_bit_cleared(u64 old_spte, u64 new_spte, u64 bit_mask) +static bool is_accessed_spte(u64 spte) { - return (old_spte & bit_mask) && !(new_spte & bit_mask); + return shadow_accessed_mask ? spte & shadow_accessed_mask + : !is_access_track_spte(spte); } -static bool spte_is_bit_changed(u64 old_spte, u64 new_spte, u64 bit_mask) +static bool is_dirty_spte(u64 spte) { - return (old_spte & bit_mask) != (new_spte & bit_mask); + return shadow_dirty_mask ? spte & shadow_dirty_mask + : spte & PT_WRITABLE_MASK; } /* Rules for using mmu_spte_set: @@ -525,25 +581,19 @@ static void mmu_spte_set(u64 *sptep, u64 new_spte) __set_spte(sptep, new_spte); } -/* Rules for using mmu_spte_update: - * Update the state bits, it means the mapped pfn is not changed. - * - * Whenever we overwrite a writable spte with a read-only one we - * should flush remote TLBs. Otherwise rmap_write_protect - * will find a read-only spte, even though the writable spte - * might be cached on a CPU's TLB, the return value indicates this - * case. +/* + * Update the SPTE (excluding the PFN), but do not track changes in its + * accessed/dirty status. */ -static bool mmu_spte_update(u64 *sptep, u64 new_spte) +static u64 mmu_spte_update_no_track(u64 *sptep, u64 new_spte) { u64 old_spte = *sptep; - bool ret = false; WARN_ON(!is_shadow_present_pte(new_spte)); if (!is_shadow_present_pte(old_spte)) { mmu_spte_set(sptep, new_spte); - return ret; + return old_spte; } if (!spte_has_volatile_bits(old_spte)) @@ -551,45 +601,62 @@ static bool mmu_spte_update(u64 *sptep, u64 new_spte) else old_spte = __update_clear_spte_slow(sptep, new_spte); + WARN_ON(spte_to_pfn(old_spte) != spte_to_pfn(new_spte)); + + return old_spte; +} + +/* Rules for using mmu_spte_update: + * Update the state bits, it means the mapped pfn is not changed. + * + * Whenever we overwrite a writable spte with a read-only one we + * should flush remote TLBs. Otherwise rmap_write_protect + * will find a read-only spte, even though the writable spte + * might be cached on a CPU's TLB, the return value indicates this + * case. + * + * Returns true if the TLB needs to be flushed + */ +static bool mmu_spte_update(u64 *sptep, u64 new_spte) +{ + bool flush = false; + u64 old_spte = mmu_spte_update_no_track(sptep, new_spte); + + if (!is_shadow_present_pte(old_spte)) + return false; + /* * For the spte updated out of mmu-lock is safe, since * we always atomically update it, see the comments in * spte_has_volatile_bits(). */ - if (spte_is_locklessly_modifiable(old_spte) && + if (spte_can_locklessly_be_made_writable(old_spte) && !is_writable_pte(new_spte)) - ret = true; - - if (!shadow_accessed_mask) { - /* - * We don't set page dirty when dropping non-writable spte. - * So do it now if the new spte is becoming non-writable. - */ - if (ret) - kvm_set_pfn_dirty(spte_to_pfn(old_spte)); - return ret; - } + flush = true; /* - * Flush TLB when accessed/dirty bits are changed in the page tables, + * Flush TLB when accessed/dirty states are changed in the page tables, * to guarantee consistency between TLB and page tables. */ - if (spte_is_bit_changed(old_spte, new_spte, - shadow_accessed_mask | shadow_dirty_mask)) - ret = true; - if (spte_is_bit_cleared(old_spte, new_spte, shadow_accessed_mask)) + if (is_accessed_spte(old_spte) && !is_accessed_spte(new_spte)) { + flush = true; kvm_set_pfn_accessed(spte_to_pfn(old_spte)); - if (spte_is_bit_cleared(old_spte, new_spte, shadow_dirty_mask)) + } + + if (is_dirty_spte(old_spte) && !is_dirty_spte(new_spte)) { + flush = true; kvm_set_pfn_dirty(spte_to_pfn(old_spte)); + } - return ret; + return flush; } /* * Rules for using mmu_spte_clear_track_bits: * It sets the sptep from present to nonpresent, and track the * state bits, it is used to clear the last level sptep. + * Returns non-zero if the PTE was previously valid. */ static int mmu_spte_clear_track_bits(u64 *sptep) { @@ -613,11 +680,12 @@ static int mmu_spte_clear_track_bits(u64 *sptep) */ WARN_ON(!kvm_is_reserved_pfn(pfn) && !page_count(pfn_to_page(pfn))); - if (!shadow_accessed_mask || old_spte & shadow_accessed_mask) + if (is_accessed_spte(old_spte)) kvm_set_pfn_accessed(pfn); - if (old_spte & (shadow_dirty_mask ? shadow_dirty_mask : - PT_WRITABLE_MASK)) + + if (is_dirty_spte(old_spte)) kvm_set_pfn_dirty(pfn); + return 1; } @@ -636,6 +704,78 @@ static u64 mmu_spte_get_lockless(u64 *sptep) return __get_spte_lockless(sptep); } +static u64 mark_spte_for_access_track(u64 spte) +{ + if (shadow_accessed_mask != 0) + return spte & ~shadow_accessed_mask; + + if (shadow_acc_track_mask == 0 || is_access_track_spte(spte)) + return spte; + + /* + * Making an Access Tracking PTE will result in removal of write access + * from the PTE. So, verify that we will be able to restore the write + * access in the fast page fault path later on. + */ + WARN_ONCE((spte & PT_WRITABLE_MASK) && + !spte_can_locklessly_be_made_writable(spte), + "kvm: Writable SPTE is not locklessly dirty-trackable\n"); + + WARN_ONCE(spte & (shadow_acc_track_saved_bits_mask << + shadow_acc_track_saved_bits_shift), + "kvm: Access Tracking saved bit locations are not zero\n"); + + spte |= (spte & shadow_acc_track_saved_bits_mask) << + shadow_acc_track_saved_bits_shift; + spte &= ~shadow_acc_track_mask; + spte |= shadow_acc_track_value; + + return spte; +} + +/* Restore an acc-track PTE back to a regular PTE */ +static u64 restore_acc_track_spte(u64 spte) +{ + u64 new_spte = spte; + u64 saved_bits = (spte >> shadow_acc_track_saved_bits_shift) + & shadow_acc_track_saved_bits_mask; + + WARN_ON_ONCE(!is_access_track_spte(spte)); + + new_spte &= ~shadow_acc_track_mask; + new_spte &= ~(shadow_acc_track_saved_bits_mask << + shadow_acc_track_saved_bits_shift); + new_spte |= saved_bits; + + return new_spte; +} + +/* Returns the Accessed status of the PTE and resets it at the same time. */ +static bool mmu_spte_age(u64 *sptep) +{ + u64 spte = mmu_spte_get_lockless(sptep); + + if (!is_accessed_spte(spte)) + return false; + + if (shadow_accessed_mask) { + clear_bit((ffs(shadow_accessed_mask) - 1), + (unsigned long *)sptep); + } else { + /* + * Capture the dirty status of the page, so that it doesn't get + * lost when the SPTE is marked for access tracking. + */ + if (is_writable_pte(spte)) + kvm_set_pfn_dirty(spte_to_pfn(spte)); + + spte = mark_spte_for_access_track(spte); + mmu_spte_update_no_track(sptep, spte); + } + + return true; +} + static void walk_shadow_page_lockless_begin(struct kvm_vcpu *vcpu) { /* @@ -1212,7 +1352,7 @@ static bool spte_write_protect(u64 *sptep, bool pt_protect) u64 spte = *sptep; if (!is_writable_pte(spte) && - !(pt_protect && spte_is_locklessly_modifiable(spte))) + !(pt_protect && spte_can_locklessly_be_made_writable(spte))) return false; rmap_printk("rmap_write_protect: spte %p %llx\n", sptep, *sptep); @@ -1420,7 +1560,7 @@ static int kvm_set_pte_rmapp(struct kvm *kvm, struct kvm_rmap_head *rmap_head, restart: for_each_rmap_spte(rmap_head, &iter, sptep) { rmap_printk("kvm_set_pte_rmapp: spte %p %llx gfn %llx (%d)\n", - sptep, *sptep, gfn, level); + sptep, *sptep, gfn, level); need_flush = 1; @@ -1433,7 +1573,8 @@ restart: new_spte &= ~PT_WRITABLE_MASK; new_spte &= ~SPTE_HOST_WRITEABLE; - new_spte &= ~shadow_accessed_mask; + + new_spte = mark_spte_for_access_track(new_spte); mmu_spte_clear_track_bits(sptep); mmu_spte_set(sptep, new_spte); @@ -1595,15 +1736,8 @@ static int kvm_age_rmapp(struct kvm *kvm, struct kvm_rmap_head *rmap_head, struct rmap_iterator uninitialized_var(iter); int young = 0; - BUG_ON(!shadow_accessed_mask); - - for_each_rmap_spte(rmap_head, &iter, sptep) { - if (*sptep & shadow_accessed_mask) { - young = 1; - clear_bit((ffs(shadow_accessed_mask) - 1), - (unsigned long *)sptep); - } - } + for_each_rmap_spte(rmap_head, &iter, sptep) + young |= mmu_spte_age(sptep); trace_kvm_age_page(gfn, level, slot, young); return young; @@ -1615,24 +1749,20 @@ static int kvm_test_age_rmapp(struct kvm *kvm, struct kvm_rmap_head *rmap_head, { u64 *sptep; struct rmap_iterator iter; - int young = 0; /* - * If there's no access bit in the secondary pte set by the - * hardware it's up to gup-fast/gup to set the access bit in - * the primary pte or in the page structure. + * If there's no access bit in the secondary pte set by the hardware and + * fast access tracking is also not enabled, it's up to gup-fast/gup to + * set the access bit in the primary pte or in the page structure. */ - if (!shadow_accessed_mask) + if (!shadow_accessed_mask && !shadow_acc_track_mask) goto out; - for_each_rmap_spte(rmap_head, &iter, sptep) { - if (*sptep & shadow_accessed_mask) { - young = 1; - break; - } - } + for_each_rmap_spte(rmap_head, &iter, sptep) + if (is_accessed_spte(*sptep)) + return 1; out: - return young; + return 0; } #define RMAP_RECYCLE_THRESHOLD 1000 @@ -1660,7 +1790,7 @@ int kvm_age_hva(struct kvm *kvm, unsigned long start, unsigned long end) * This has some overhead, but not as much as the cost of swapping * out actively used pages or breaking up actively used hugepages. */ - if (!shadow_accessed_mask) + if (!shadow_accessed_mask && !shadow_acc_track_mask) return kvm_handle_hva_range(kvm, start, end, 0, kvm_unmap_rmapp); @@ -1713,7 +1843,7 @@ static void kvm_mmu_free_page(struct kvm_mmu_page *sp) static unsigned kvm_page_table_hashfn(gfn_t gfn) { - return gfn & ((1 << KVM_MMU_HASH_SHIFT) - 1); + return hash_64(gfn, KVM_MMU_HASH_SHIFT); } static void mmu_page_add_parent_pte(struct kvm_vcpu *vcpu, @@ -1904,17 +2034,17 @@ static void kvm_mmu_commit_zap_page(struct kvm *kvm, * since it has been deleted from active_mmu_pages but still can be found * at hast list. * - * for_each_gfn_valid_sp() has skipped that kind of pages. + * for_each_valid_sp() has skipped that kind of pages. */ -#define for_each_gfn_valid_sp(_kvm, _sp, _gfn) \ +#define for_each_valid_sp(_kvm, _sp, _gfn) \ hlist_for_each_entry(_sp, \ &(_kvm)->arch.mmu_page_hash[kvm_page_table_hashfn(_gfn)], hash_link) \ - if ((_sp)->gfn != (_gfn) || is_obsolete_sp((_kvm), (_sp)) \ - || (_sp)->role.invalid) {} else + if (is_obsolete_sp((_kvm), (_sp)) || (_sp)->role.invalid) { \ + } else #define for_each_gfn_indirect_valid_sp(_kvm, _sp, _gfn) \ - for_each_gfn_valid_sp(_kvm, _sp, _gfn) \ - if ((_sp)->role.direct) {} else + for_each_valid_sp(_kvm, _sp, _gfn) \ + if ((_sp)->gfn != (_gfn) || (_sp)->role.direct) {} else /* @sp->gfn should be write-protected at the call site */ static bool __kvm_sync_page(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp, @@ -2116,6 +2246,7 @@ static struct kvm_mmu_page *kvm_mmu_get_page(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp; bool need_sync = false; bool flush = false; + int collisions = 0; LIST_HEAD(invalid_list); role = vcpu->arch.mmu.base_role; @@ -2130,7 +2261,12 @@ static struct kvm_mmu_page *kvm_mmu_get_page(struct kvm_vcpu *vcpu, quadrant &= (1 << ((PT32_PT_BITS - PT64_PT_BITS) * level)) - 1; role.quadrant = quadrant; } - for_each_gfn_valid_sp(vcpu->kvm, sp, gfn) { + for_each_valid_sp(vcpu->kvm, sp, gfn) { + if (sp->gfn != gfn) { + collisions++; + continue; + } + if (!need_sync && sp->unsync) need_sync = true; @@ -2153,7 +2289,7 @@ static struct kvm_mmu_page *kvm_mmu_get_page(struct kvm_vcpu *vcpu, __clear_sp_write_flooding_count(sp); trace_kvm_mmu_get_page(sp, false); - return sp; + goto out; } ++vcpu->kvm->stat.mmu_cache_miss; @@ -2183,6 +2319,9 @@ static struct kvm_mmu_page *kvm_mmu_get_page(struct kvm_vcpu *vcpu, trace_kvm_mmu_get_page(sp, true); kvm_mmu_flush_or_zap(vcpu, &invalid_list, false, flush); +out: + if (collisions > vcpu->kvm->stat.max_mmu_page_hash_collisions) + vcpu->kvm->stat.max_mmu_page_hash_collisions = collisions; return sp; } @@ -2583,6 +2722,9 @@ static int set_spte(struct kvm_vcpu *vcpu, u64 *sptep, spte |= shadow_dirty_mask; } + if (speculative) + spte = mark_spte_for_access_track(spte); + set_pte: if (mmu_spte_update(sptep, spte)) kvm_flush_remote_tlbs(vcpu->kvm); @@ -2636,7 +2778,7 @@ static bool mmu_set_spte(struct kvm_vcpu *vcpu, u64 *sptep, unsigned pte_access, pgprintk("%s: setting spte %llx\n", __func__, *sptep); pgprintk("instantiating %s PTE (%s) at %llx (%llx) addr %p\n", is_large_pte(*sptep)? "2MB" : "4kB", - *sptep & PT_PRESENT_MASK ?"RW":"R", gfn, + *sptep & PT_WRITABLE_MASK ? "RW" : "R", gfn, *sptep, sptep); if (!was_rmapped && is_large_pte(*sptep)) ++vcpu->kvm->stat.lpages; @@ -2869,33 +3011,43 @@ static bool page_fault_can_be_fast(u32 error_code) if (unlikely(error_code & PFERR_RSVD_MASK)) return false; + /* See if the page fault is due to an NX violation */ + if (unlikely(((error_code & (PFERR_FETCH_MASK | PFERR_PRESENT_MASK)) + == (PFERR_FETCH_MASK | PFERR_PRESENT_MASK)))) + return false; + /* - * #PF can be fast only if the shadow page table is present and it - * is caused by write-protect, that means we just need change the - * W bit of the spte which can be done out of mmu-lock. + * #PF can be fast if: + * 1. The shadow page table entry is not present, which could mean that + * the fault is potentially caused by access tracking (if enabled). + * 2. The shadow page table entry is present and the fault + * is caused by write-protect, that means we just need change the W + * bit of the spte which can be done out of mmu-lock. + * + * However, if access tracking is disabled we know that a non-present + * page must be a genuine page fault where we have to create a new SPTE. + * So, if access tracking is disabled, we return true only for write + * accesses to a present page. */ - if (!(error_code & PFERR_PRESENT_MASK) || - !(error_code & PFERR_WRITE_MASK)) - return false; - return true; + return shadow_acc_track_mask != 0 || + ((error_code & (PFERR_WRITE_MASK | PFERR_PRESENT_MASK)) + == (PFERR_WRITE_MASK | PFERR_PRESENT_MASK)); } +/* + * Returns true if the SPTE was fixed successfully. Otherwise, + * someone else modified the SPTE from its original value. + */ static bool fast_pf_fix_direct_spte(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp, - u64 *sptep, u64 spte) + u64 *sptep, u64 old_spte, u64 new_spte) { gfn_t gfn; WARN_ON(!sp->role.direct); /* - * The gfn of direct spte is stable since it is calculated - * by sp->gfn. - */ - gfn = kvm_mmu_page_get_gfn(sp, sptep - sp->spt); - - /* * Theoretically we could also set dirty bit (and flush TLB) here in * order to eliminate unnecessary PML logging. See comments in * set_spte. But fast_page_fault is very unlikely to happen with PML @@ -2907,12 +3059,33 @@ fast_pf_fix_direct_spte(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp, * * Compare with set_spte where instead shadow_dirty_mask is set. */ - if (cmpxchg64(sptep, spte, spte | PT_WRITABLE_MASK) == spte) + if (cmpxchg64(sptep, old_spte, new_spte) != old_spte) + return false; + + if (is_writable_pte(new_spte) && !is_writable_pte(old_spte)) { + /* + * The gfn of direct spte is stable since it is + * calculated by sp->gfn. + */ + gfn = kvm_mmu_page_get_gfn(sp, sptep - sp->spt); kvm_vcpu_mark_page_dirty(vcpu, gfn); + } return true; } +static bool is_access_allowed(u32 fault_err_code, u64 spte) +{ + if (fault_err_code & PFERR_FETCH_MASK) + return is_executable_pte(spte); + + if (fault_err_code & PFERR_WRITE_MASK) + return is_writable_pte(spte); + + /* Fault was on Read access */ + return spte & PT_PRESENT_MASK; +} + /* * Return value: * - true: let the vcpu to access on the same address again. @@ -2923,8 +3096,9 @@ static bool fast_page_fault(struct kvm_vcpu *vcpu, gva_t gva, int level, { struct kvm_shadow_walk_iterator iterator; struct kvm_mmu_page *sp; - bool ret = false; + bool fault_handled = false; u64 spte = 0ull; + uint retry_count = 0; if (!VALID_PAGE(vcpu->arch.mmu.root_hpa)) return false; @@ -2933,66 +3107,93 @@ static bool fast_page_fault(struct kvm_vcpu *vcpu, gva_t gva, int level, return false; walk_shadow_page_lockless_begin(vcpu); - for_each_shadow_entry_lockless(vcpu, gva, iterator, spte) - if (!is_shadow_present_pte(spte) || iterator.level < level) + + do { + u64 new_spte; + + for_each_shadow_entry_lockless(vcpu, gva, iterator, spte) + if (!is_shadow_present_pte(spte) || + iterator.level < level) + break; + + sp = page_header(__pa(iterator.sptep)); + if (!is_last_spte(spte, sp->role.level)) break; - /* - * If the mapping has been changed, let the vcpu fault on the - * same address again. - */ - if (!is_shadow_present_pte(spte)) { - ret = true; - goto exit; - } + /* + * Check whether the memory access that caused the fault would + * still cause it if it were to be performed right now. If not, + * then this is a spurious fault caused by TLB lazily flushed, + * or some other CPU has already fixed the PTE after the + * current CPU took the fault. + * + * Need not check the access of upper level table entries since + * they are always ACC_ALL. + */ + if (is_access_allowed(error_code, spte)) { + fault_handled = true; + break; + } - sp = page_header(__pa(iterator.sptep)); - if (!is_last_spte(spte, sp->role.level)) - goto exit; + new_spte = spte; - /* - * Check if it is a spurious fault caused by TLB lazily flushed. - * - * Need not check the access of upper level table entries since - * they are always ACC_ALL. - */ - if (is_writable_pte(spte)) { - ret = true; - goto exit; - } + if (is_access_track_spte(spte)) + new_spte = restore_acc_track_spte(new_spte); - /* - * Currently, to simplify the code, only the spte write-protected - * by dirty-log can be fast fixed. - */ - if (!spte_is_locklessly_modifiable(spte)) - goto exit; + /* + * Currently, to simplify the code, write-protection can + * be removed in the fast path only if the SPTE was + * write-protected for dirty-logging or access tracking. + */ + if ((error_code & PFERR_WRITE_MASK) && + spte_can_locklessly_be_made_writable(spte)) + { + new_spte |= PT_WRITABLE_MASK; - /* - * Do not fix write-permission on the large spte since we only dirty - * the first page into the dirty-bitmap in fast_pf_fix_direct_spte() - * that means other pages are missed if its slot is dirty-logged. - * - * Instead, we let the slow page fault path create a normal spte to - * fix the access. - * - * See the comments in kvm_arch_commit_memory_region(). - */ - if (sp->role.level > PT_PAGE_TABLE_LEVEL) - goto exit; + /* + * Do not fix write-permission on the large spte. Since + * we only dirty the first page into the dirty-bitmap in + * fast_pf_fix_direct_spte(), other pages are missed + * if its slot has dirty logging enabled. + * + * Instead, we let the slow page fault path create a + * normal spte to fix the access. + * + * See the comments in kvm_arch_commit_memory_region(). + */ + if (sp->role.level > PT_PAGE_TABLE_LEVEL) + break; + } + + /* Verify that the fault can be handled in the fast path */ + if (new_spte == spte || + !is_access_allowed(error_code, new_spte)) + break; + + /* + * Currently, fast page fault only works for direct mapping + * since the gfn is not stable for indirect shadow page. See + * Documentation/virtual/kvm/locking.txt to get more detail. + */ + fault_handled = fast_pf_fix_direct_spte(vcpu, sp, + iterator.sptep, spte, + new_spte); + if (fault_handled) + break; + + if (++retry_count > 4) { + printk_once(KERN_WARNING + "kvm: Fast #PF retrying more than 4 times.\n"); + break; + } + + } while (true); - /* - * Currently, fast page fault only works for direct mapping since - * the gfn is not stable for indirect shadow page. - * See Documentation/virtual/kvm/locking.txt to get more detail. - */ - ret = fast_pf_fix_direct_spte(vcpu, sp, iterator.sptep, spte); -exit: trace_fast_page_fault(vcpu, gva, error_code, iterator.sptep, - spte, ret); + spte, fault_handled); walk_shadow_page_lockless_end(vcpu); - return ret; + return fault_handled; } static bool try_async_pf(struct kvm_vcpu *vcpu, bool prefault, gfn_t gfn, @@ -5063,6 +5264,8 @@ static void mmu_destroy_caches(void) int kvm_mmu_module_init(void) { + kvm_mmu_clear_all_pte_masks(); + pte_list_desc_cache = kmem_cache_create("pte_list_desc", sizeof(struct pte_list_desc), 0, 0, NULL); |