Now that the shadow MMU and TDP MMU have identical logic for detecting required TLB flushes when updating SPTEs, move said logic to a helper so that the TDP MMU code can benefit from the comments that are currently exclusive to the shadow MMU. No functional change intended. Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx> --- arch/x86/kvm/mmu/mmu.c | 19 +------------------ arch/x86/kvm/mmu/spte.h | 29 +++++++++++++++++++++++++++++ arch/x86/kvm/mmu/tdp_mmu.c | 3 +-- 3 files changed, 31 insertions(+), 20 deletions(-) diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index 5be3b5f054f1..f75915ff33be 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -488,23 +488,6 @@ static void mmu_spte_set(u64 *sptep, u64 new_spte) /* Rules for using mmu_spte_update: * Update the state bits, it means the mapped pfn is not changed. * - * If the MMU-writable flag is cleared, i.e. the SPTE is write-protected for - * write-tracking, remote TLBs must be flushed, even if the SPTE was read-only, - * as KVM allows stale Writable TLB entries to exist. When dirty logging, KVM - * flushes TLBs based on whether or not dirty bitmap/ring entries were reaped, - * not whether or not SPTEs were modified, i.e. only the write-tracking case - * needs to flush at the time the SPTEs is modified, before dropping mmu_lock. - * - * Don't flush if the Accessed bit is cleared, as access tracking tolerates - * false negatives, and the one path that does care about TLB flushes, - * kvm_mmu_notifier_clear_flush_young(), flushes if a young SPTE is found, i.e. - * doesn't rely on lower helpers to detect the need to flush. - * - * Lastly, don't flush if the Dirty bit is cleared, as KVM unconditionally - * flushes when enabling dirty logging (see kvm_mmu_slot_apply_flags()), and - * when clearing dirty logs, KVM flushes based on whether or not dirty entries - * were reaped from the bitmap/ring, not whether or not dirty SPTEs were found. - * * Returns true if the TLB needs to be flushed */ static bool mmu_spte_update(u64 *sptep, u64 new_spte) @@ -527,7 +510,7 @@ static bool mmu_spte_update(u64 *sptep, u64 new_spte) WARN_ON_ONCE(!is_shadow_present_pte(old_spte) || spte_to_pfn(old_spte) != spte_to_pfn(new_spte)); - return is_mmu_writable_spte(old_spte) && !is_mmu_writable_spte(new_spte); + return is_tlb_flush_required_for_leaf_spte(old_spte, new_spte); } /* diff --git a/arch/x86/kvm/mmu/spte.h b/arch/x86/kvm/mmu/spte.h index c8dc75337c8b..a404279ba731 100644 --- a/arch/x86/kvm/mmu/spte.h +++ b/arch/x86/kvm/mmu/spte.h @@ -467,6 +467,35 @@ static inline bool is_mmu_writable_spte(u64 spte) return spte & shadow_mmu_writable_mask; } +/* + * If the MMU-writable flag is cleared, i.e. the SPTE is write-protected for + * write-tracking, remote TLBs must be flushed, even if the SPTE was read-only, + * as KVM allows stale Writable TLB entries to exist. When dirty logging, KVM + * flushes TLBs based on whether or not dirty bitmap/ring entries were reaped, + * not whether or not SPTEs were modified, i.e. only the write-tracking case + * needs to flush at the time the SPTEs is modified, before dropping mmu_lock. + * + * Don't flush if the Accessed bit is cleared, as access tracking tolerates + * false negatives, and the one path that does care about TLB flushes, + * kvm_mmu_notifier_clear_flush_young(), flushes if a young SPTE is found, i.e. + * doesn't rely on lower helpers to detect the need to flush. + * + * Lastly, don't flush if the Dirty bit is cleared, as KVM unconditionally + * flushes when enabling dirty logging (see kvm_mmu_slot_apply_flags()), and + * when clearing dirty logs, KVM flushes based on whether or not dirty entries + * were reaped from the bitmap/ring, not whether or not dirty SPTEs were found. + * + * Note, this logic only applies to shadow-present leaf SPTEs. The caller is + * responsible for checking that the old SPTE is shadow-present, and is also + * responsible for determining whether or not a TLB flush is required when + * modifying a shadow-present non-leaf SPTE. + */ +static inline bool is_tlb_flush_required_for_leaf_spte(u64 old_spte, + u64 new_spte) +{ + return is_mmu_writable_spte(old_spte) && !is_mmu_writable_spte(new_spte); +} + static inline u64 get_mmio_spte_generation(u64 spte) { u64 gen; diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c index f412bca206c5..615c6a84fd60 100644 --- a/arch/x86/kvm/mmu/tdp_mmu.c +++ b/arch/x86/kvm/mmu/tdp_mmu.c @@ -1034,8 +1034,7 @@ static int tdp_mmu_map_handle_target_level(struct kvm_vcpu *vcpu, return RET_PF_RETRY; else if (is_shadow_present_pte(iter->old_spte) && (!is_last_spte(iter->old_spte, iter->level) || - WARN_ON_ONCE(is_mmu_writable_spte(iter->old_spte) && - !is_mmu_writable_spte(new_spte)))) + WARN_ON_ONCE(is_tlb_flush_required_for_leaf_spte(iter->old_spte, new_spte)))) kvm_flush_remote_tlbs_gfn(vcpu->kvm, iter->gfn, iter->level); /* -- 2.47.0.rc1.288.g06298d1525-goog