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The new bit is used to avoid triggering a page_count() == 0 warning and to avoid touching A/D bits of unknown usage. Non-EPT sptes don't have any free bits to use, so this tracking is not possible when TDP is disabled or on 32-bit x86. Signed-off-by: David Stevens --- arch/x86/kvm/mmu/mmu.c | 47 ++++++++++++++++++++-------------- arch/x86/kvm/mmu/paging_tmpl.h | 5 ++-- arch/x86/kvm/mmu/spte.c | 5 +++- arch/x86/kvm/mmu/spte.h | 16 +++++++++++- arch/x86/kvm/mmu/tdp_mmu.c | 21 ++++++++------- include/linux/kvm_host.h | 3 +++ virt/kvm/kvm_main.c | 6 +++-- 7 files changed, 69 insertions(+), 34 deletions(-) diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index bbeb0f6783d7..4936a8c5829b 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -541,12 +541,14 @@ static bool mmu_spte_update(u64 *sptep, u64 new_spte) if (is_accessed_spte(old_spte) && !is_accessed_spte(new_spte)) { flush = true; - kvm_set_pfn_accessed(spte_to_pfn(old_spte)); + if (is_refcounted_page_spte(old_spte)) + kvm_set_page_accessed(pfn_to_page(spte_to_pfn(old_spte))); } if (is_dirty_spte(old_spte) && !is_dirty_spte(new_spte)) { flush = true; - kvm_set_pfn_dirty(spte_to_pfn(old_spte)); + if (is_refcounted_page_spte(old_spte)) + kvm_set_page_dirty(pfn_to_page(spte_to_pfn(old_spte))); } return flush; @@ -578,20 +580,23 @@ static u64 mmu_spte_clear_track_bits(struct kvm *kvm, u64 *sptep) pfn = spte_to_pfn(old_spte); - /* - * KVM doesn't hold a reference to any pages mapped into the guest, and - * instead uses the mmu_notifier to ensure that KVM unmaps any pages - * before they are reclaimed. Sanity check that, if the pfn is backed - * by a refcounted page, the refcount is elevated. - */ - page = kvm_pfn_to_refcounted_page(pfn); - WARN_ON_ONCE(page && !page_count(page)); + if (is_refcounted_page_spte(old_spte)) { + /* + * KVM doesn't hold a reference to any pages mapped into the + * guest, and instead uses the mmu_notifier to ensure that KVM + * unmaps any pages before they are reclaimed. Sanity check + * that, if the pfn is backed by a refcounted page, the + * refcount is elevated. + */ + page = kvm_pfn_to_refcounted_page(pfn); + WARN_ON_ONCE(!page || !page_count(page)); - if (is_accessed_spte(old_spte)) - kvm_set_pfn_accessed(pfn); + if (is_accessed_spte(old_spte)) + kvm_set_page_accessed(pfn_to_page(pfn)); - if (is_dirty_spte(old_spte)) - kvm_set_pfn_dirty(pfn); + if (is_dirty_spte(old_spte)) + kvm_set_page_dirty(pfn_to_page(pfn)); + } return old_spte; } @@ -627,8 +632,8 @@ static bool mmu_spte_age(u64 *sptep) * 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)); + if (is_writable_pte(spte) && is_refcounted_page_spte(spte)) + kvm_set_page_dirty(pfn_to_page(spte_to_pfn(spte))); spte = mark_spte_for_access_track(spte); mmu_spte_update_no_track(sptep, spte); @@ -1267,8 +1272,8 @@ static bool spte_wrprot_for_clear_dirty(u64 *sptep) { bool was_writable = test_and_clear_bit(PT_WRITABLE_SHIFT, (unsigned long *)sptep); - if (was_writable && !spte_ad_enabled(*sptep)) - kvm_set_pfn_dirty(spte_to_pfn(*sptep)); + if (was_writable && !spte_ad_enabled(*sptep) && is_refcounted_page_spte(*sptep)) + kvm_set_page_dirty(pfn_to_page(spte_to_pfn(*sptep))); return was_writable; } @@ -2946,7 +2951,7 @@ static int mmu_set_spte(struct kvm_vcpu *vcpu, struct kvm_memory_slot *slot, } wrprot = make_spte(vcpu, sp, slot, pte_access, gfn, pfn, *sptep, prefetch, - true, host_writable, &spte); + true, host_writable, true, &spte); if (*sptep == spte) { ret = RET_PF_SPURIOUS; @@ -5999,6 +6004,10 @@ void kvm_configure_mmu(bool enable_tdp, int tdp_forced_root_level, #ifdef CONFIG_X86_64 tdp_mmu_enabled = tdp_mmu_allowed && tdp_enabled; + + /* The SPTE_MMU_PAGE_REFCOUNTED bit is only available with EPT. */ + if (enable_tdp) + shadow_refcounted_mask = SPTE_MMU_PAGE_REFCOUNTED; #endif /* * max_huge_page_level reflects KVM's MMU capabilities irrespective diff --git a/arch/x86/kvm/mmu/paging_tmpl.h b/arch/x86/kvm/mmu/paging_tmpl.h index 4d4e98fe4f35..c965f77ac4d5 100644 --- a/arch/x86/kvm/mmu/paging_tmpl.h +++ b/arch/x86/kvm/mmu/paging_tmpl.h @@ -902,7 +902,7 @@ static gpa_t FNAME(gva_to_gpa)(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu, */ static int FNAME(sync_spte)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp, int i) { - bool host_writable; + bool host_writable, is_refcounted; gpa_t first_pte_gpa; u64 *sptep, spte; struct kvm_memory_slot *slot; @@ -959,10 +959,11 @@ static int FNAME(sync_spte)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp, int sptep = &sp->spt[i]; spte = *sptep; host_writable = spte & shadow_host_writable_mask; + is_refcounted = is_refcounted_page_spte(spte); slot = kvm_vcpu_gfn_to_memslot(vcpu, gfn); make_spte(vcpu, sp, slot, pte_access, gfn, spte_to_pfn(spte), spte, true, false, - host_writable, &spte); + host_writable, is_refcounted, &spte); return mmu_spte_update(sptep, spte); } diff --git a/arch/x86/kvm/mmu/spte.c b/arch/x86/kvm/mmu/spte.c index 4a599130e9c9..e4a458b7e185 100644 --- a/arch/x86/kvm/mmu/spte.c +++ b/arch/x86/kvm/mmu/spte.c @@ -39,6 +39,7 @@ u64 __read_mostly shadow_memtype_mask; u64 __read_mostly shadow_me_value; u64 __read_mostly shadow_me_mask; u64 __read_mostly shadow_acc_track_mask; +u64 __read_mostly shadow_refcounted_mask; u64 __read_mostly shadow_nonpresent_or_rsvd_mask; u64 __read_mostly shadow_nonpresent_or_rsvd_lower_gfn_mask; @@ -138,7 +139,7 @@ bool make_spte(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp, const struct kvm_memory_slot *slot, unsigned int pte_access, gfn_t gfn, kvm_pfn_t pfn, u64 old_spte, bool prefetch, bool can_unsync, - bool host_writable, u64 *new_spte) + bool host_writable, bool is_refcounted, u64 *new_spte) { int level = sp->role.level; u64 spte = SPTE_MMU_PRESENT_MASK; @@ -188,6 +189,8 @@ bool make_spte(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp, if (level > PG_LEVEL_4K) spte |= PT_PAGE_SIZE_MASK; + if (is_refcounted) + spte |= shadow_refcounted_mask; if (shadow_memtype_mask) spte |= static_call(kvm_x86_get_mt_mask)(vcpu, gfn, diff --git a/arch/x86/kvm/mmu/spte.h b/arch/x86/kvm/mmu/spte.h index a129951c9a88..6bf0069d8db6 100644 --- a/arch/x86/kvm/mmu/spte.h +++ b/arch/x86/kvm/mmu/spte.h @@ -96,6 +96,13 @@ static_assert(!(EPT_SPTE_MMU_WRITABLE & SHADOW_ACC_TRACK_SAVED_MASK)); /* Defined only to keep the above static asserts readable. */ #undef SHADOW_ACC_TRACK_SAVED_MASK +/* + * Indicates that the SPTE refers to a page with a valid refcount. Only + * available for TDP SPTEs, since bits 62:52 are reserved for PAE paging, + * including NPT PAE. + */ +#define SPTE_MMU_PAGE_REFCOUNTED BIT_ULL(59) + /* * Due to limited space in PTEs, the MMIO generation is a 19 bit subset of * the memslots generation and is derived as follows: @@ -345,6 +352,13 @@ static inline bool is_dirty_spte(u64 spte) return dirty_mask ? spte & dirty_mask : spte & PT_WRITABLE_MASK; } +extern u64 __read_mostly shadow_refcounted_mask; + +static inline bool is_refcounted_page_spte(u64 spte) +{ + return !shadow_refcounted_mask || (spte & shadow_refcounted_mask); +} + static inline u64 get_rsvd_bits(struct rsvd_bits_validate *rsvd_check, u64 pte, int level) { @@ -475,7 +489,7 @@ bool make_spte(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp, const struct kvm_memory_slot *slot, unsigned int pte_access, gfn_t gfn, kvm_pfn_t pfn, u64 old_spte, bool prefetch, bool can_unsync, - bool host_writable, u64 *new_spte); + bool host_writable, bool is_refcounted, u64 *new_spte); u64 make_huge_page_split_spte(struct kvm *kvm, u64 huge_spte, union kvm_mmu_page_role role, int index); u64 make_nonleaf_spte(u64 *child_pt, bool ad_disabled); diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c index 6ae19b4ee5b1..ee497fb78d90 100644 --- a/arch/x86/kvm/mmu/tdp_mmu.c +++ b/arch/x86/kvm/mmu/tdp_mmu.c @@ -414,6 +414,7 @@ static void handle_changed_spte(struct kvm *kvm, int as_id, gfn_t gfn, bool was_leaf = was_present && is_last_spte(old_spte, level); bool is_leaf = is_present && is_last_spte(new_spte, level); bool pfn_changed = spte_to_pfn(old_spte) != spte_to_pfn(new_spte); + bool is_refcounted = is_refcounted_page_spte(old_spte); WARN_ON_ONCE(level > PT64_ROOT_MAX_LEVEL); WARN_ON_ONCE(level < PG_LEVEL_4K); @@ -478,9 +479,9 @@ static void handle_changed_spte(struct kvm *kvm, int as_id, gfn_t gfn, if (is_leaf != was_leaf) kvm_update_page_stats(kvm, level, is_leaf ? 1 : -1); - if (was_leaf && is_dirty_spte(old_spte) && + if (was_leaf && is_dirty_spte(old_spte) && is_refcounted && (!is_present || !is_dirty_spte(new_spte) || pfn_changed)) - kvm_set_pfn_dirty(spte_to_pfn(old_spte)); + kvm_set_page_dirty(pfn_to_page(spte_to_pfn(old_spte))); /* * Recursively handle child PTs if the change removed a subtree from @@ -492,9 +493,9 @@ static void handle_changed_spte(struct kvm *kvm, int as_id, gfn_t gfn, (is_leaf || !is_present || WARN_ON_ONCE(pfn_changed))) handle_removed_pt(kvm, spte_to_child_pt(old_spte, level), shared); - if (was_leaf && is_accessed_spte(old_spte) && + if (was_leaf && is_accessed_spte(old_spte) && is_refcounted && (!is_present || !is_accessed_spte(new_spte) || pfn_changed)) - kvm_set_pfn_accessed(spte_to_pfn(old_spte)); + kvm_set_page_accessed(pfn_to_page(spte_to_pfn(old_spte))); } /* @@ -956,8 +957,8 @@ static int tdp_mmu_map_handle_target_level(struct kvm_vcpu *vcpu, new_spte = make_mmio_spte(vcpu, iter->gfn, ACC_ALL); else wrprot = make_spte(vcpu, sp, fault->slot, ACC_ALL, iter->gfn, - fault->pfn, iter->old_spte, fault->prefetch, true, - fault->map_writable, &new_spte); + fault->pfn, iter->old_spte, fault->prefetch, true, + fault->map_writable, true, &new_spte); if (new_spte == iter->old_spte) ret = RET_PF_SPURIOUS; @@ -1178,8 +1179,9 @@ static bool age_gfn_range(struct kvm *kvm, struct tdp_iter *iter, * 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(iter->old_spte)) - kvm_set_pfn_dirty(spte_to_pfn(iter->old_spte)); + if (is_writable_pte(iter->old_spte) && + is_refcounted_page_spte(iter->old_spte)) + kvm_set_page_dirty(pfn_to_page(spte_to_pfn(iter->old_spte))); new_spte = mark_spte_for_access_track(iter->old_spte); iter->old_spte = kvm_tdp_mmu_write_spte(iter->sptep, @@ -1602,7 +1604,8 @@ static void clear_dirty_pt_masked(struct kvm *kvm, struct kvm_mmu_page *root, trace_kvm_tdp_mmu_spte_changed(iter.as_id, iter.gfn, iter.level, iter.old_spte, iter.old_spte & ~dbit); - kvm_set_pfn_dirty(spte_to_pfn(iter.old_spte)); + if (is_refcounted_page_spte(iter.old_spte)) + kvm_set_page_dirty(pfn_to_page(spte_to_pfn(iter.old_spte))); } rcu_read_unlock(); diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h index 59dc9fbafc08..d19a418df04b 100644 --- a/include/linux/kvm_host.h +++ b/include/linux/kvm_host.h @@ -1211,6 +1211,9 @@ unsigned long gfn_to_hva_memslot_prot(struct kvm_memory_slot *slot, gfn_t gfn, void kvm_release_page_clean(struct page *page); void kvm_release_page_dirty(struct page *page); +void kvm_set_page_accessed(struct page *page); +void kvm_set_page_dirty(struct page *page); + struct kvm_follow_pfn { const struct kvm_memory_slot *slot; gfn_t gfn; diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 24e2269339cb..235c92830cdc 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -3277,17 +3277,19 @@ static bool kvm_is_ad_tracked_page(struct page *page) return !PageReserved(page); } -static void kvm_set_page_dirty(struct page *page) +void kvm_set_page_dirty(struct page *page) { if (kvm_is_ad_tracked_page(page)) SetPageDirty(page); } +EXPORT_SYMBOL_GPL(kvm_set_page_dirty); -static void kvm_set_page_accessed(struct page *page) +void kvm_set_page_accessed(struct page *page) { if (kvm_is_ad_tracked_page(page)) mark_page_accessed(page); } +EXPORT_SYMBOL_GPL(kvm_set_page_accessed); void kvm_release_page_clean(struct page *page) {