The patch below does not apply to the 4.9-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From 54eb3ef56f36827aad90915df33387d4c2b5df5a Mon Sep 17 00:00:00 2001 From: Sean Christopherson seanjc@google.com Date: Sat, 23 Apr 2022 03:47:42 +0000 Subject: [PATCH] KVM: x86/mmu: Move shadow-present check out of spte_has_volatile_bits()
Move the is_shadow_present_pte() check out of spte_has_volatile_bits() and into its callers. Well, caller, since only one of its two callers doesn't already do the shadow-present check.
Opportunistically move the helper to spte.c/h so that it can be used by the TDP MMU, which is also the primary motivation for the shadow-present change. Unlike the legacy MMU, the TDP MMU uses a single path for clear leaf and non-leaf SPTEs, and to avoid unnecessary atomic updates, the TDP MMU will need to check is_last_spte() prior to calling spte_has_volatile_bits(), and calling is_last_spte() without first calling is_shadow_present_spte() is at best odd, and at worst a violation of KVM's loosely defines SPTE rules.
Note, mmu_spte_clear_track_bits() could likely skip the write entirely for SPTEs that are not shadow-present. Leave that cleanup for a future patch to avoid introducing a functional change, and because the shadow-present check can likely be moved further up the stack, e.g. drop_large_spte() appears to be the only path that doesn't already explicitly check for a shadow-present SPTE.
No functional change intended.
Cc: stable@vger.kernel.org Signed-off-by: Sean Christopherson seanjc@google.com Message-Id: 20220423034752.1161007-3-seanjc@google.com Signed-off-by: Paolo Bonzini pbonzini@redhat.com
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index 48dcb6a782f4..311e4e1d7870 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -473,32 +473,6 @@ static u64 __get_spte_lockless(u64 *sptep) } #endif
-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 (!is_writable_pte(spte) && is_mmu_writable_spte(spte)) - return true; - - if (is_access_track_spte(spte)) - return true; - - if (spte_ad_enabled(spte)) { - if (!(spte & shadow_accessed_mask) || - (is_writable_pte(spte) && !(spte & shadow_dirty_mask))) - return true; - } - - return false; -} - /* Rules for using mmu_spte_set: * Set the sptep from nonpresent to present. * Note: the sptep being assigned *must* be either not present @@ -593,7 +567,8 @@ static int mmu_spte_clear_track_bits(struct kvm *kvm, u64 *sptep) u64 old_spte = *sptep; int level = sptep_to_sp(sptep)->role.level;
- if (!spte_has_volatile_bits(old_spte)) + if (!is_shadow_present_pte(old_spte) || + !spte_has_volatile_bits(old_spte)) __update_clear_spte_fast(sptep, 0ull); else old_spte = __update_clear_spte_slow(sptep, 0ull); diff --git a/arch/x86/kvm/mmu/spte.c b/arch/x86/kvm/mmu/spte.c index 4739b53c9734..e5c0b6db6f2c 100644 --- a/arch/x86/kvm/mmu/spte.c +++ b/arch/x86/kvm/mmu/spte.c @@ -90,6 +90,34 @@ static bool kvm_is_mmio_pfn(kvm_pfn_t pfn) E820_TYPE_RAM); }
+/* + * Returns true if the SPTE has bits that may be set without holding mmu_lock. + * The caller is responsible for checking if the SPTE is shadow-present, and + * for determining whether or not the caller cares about non-leaf SPTEs. + */ +bool spte_has_volatile_bits(u64 spte) +{ + /* + * 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 (!is_writable_pte(spte) && is_mmu_writable_spte(spte)) + return true; + + if (is_access_track_spte(spte)) + return true; + + if (spte_ad_enabled(spte)) { + if (!(spte & shadow_accessed_mask) || + (is_writable_pte(spte) && !(spte & shadow_dirty_mask))) + return true; + } + + return false; +} + 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, diff --git a/arch/x86/kvm/mmu/spte.h b/arch/x86/kvm/mmu/spte.h index c571784cb567..80ab0f5cff01 100644 --- a/arch/x86/kvm/mmu/spte.h +++ b/arch/x86/kvm/mmu/spte.h @@ -404,6 +404,8 @@ static inline u64 get_mmio_spte_generation(u64 spte) return gen; }
+bool spte_has_volatile_bits(u64 spte); + 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,