From 80d8bbd4a92faabc65cc5047c6b8ff1468cda1fa Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Tue, 29 Mar 2022 13:25:34 -0700 Subject: [PATCH 1/2] KVM: x86/mmu: Set lpage_disallowed in TDP MMU before setting SPTE Set lpage_disallowed in TDP MMU shadow pages before making the SP visible to other readers, i.e. before setting its SPTE. This will allow KVM to query lpage_disallowed when determining if a shadow page can be replaced by a NX huge page without violating the rules of the mitigation. Signed-off-by: Sean Christopherson --- arch/x86/kvm/mmu/mmu.c | 14 ++++++++++---- arch/x86/kvm/mmu/mmu_internal.h | 2 +- arch/x86/kvm/mmu/tdp_mmu.c | 20 ++++++++++++-------- 3 files changed, 23 insertions(+), 13 deletions(-) diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index 1361eb4599b4..5cb845fae56e 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -812,14 +812,20 @@ static void account_shadowed(struct kvm *kvm, struct kvm_mmu_page *sp) kvm_mmu_gfn_disallow_lpage(slot, gfn); } -void account_huge_nx_page(struct kvm *kvm, struct kvm_mmu_page *sp) +void __account_huge_nx_page(struct kvm *kvm, struct kvm_mmu_page *sp) { - if (sp->lpage_disallowed) - return; - ++kvm->stat.nx_lpage_splits; list_add_tail(&sp->lpage_disallowed_link, &kvm->arch.lpage_disallowed_mmu_pages); +} + +static void account_huge_nx_page(struct kvm *kvm, struct kvm_mmu_page *sp) +{ + if (sp->lpage_disallowed) + return; + + __account_huge_nx_page(kvm, sp); + sp->lpage_disallowed = true; } diff --git a/arch/x86/kvm/mmu/mmu_internal.h b/arch/x86/kvm/mmu/mmu_internal.h index 1bff453f7cbe..4a0087efa1e3 100644 --- a/arch/x86/kvm/mmu/mmu_internal.h +++ b/arch/x86/kvm/mmu/mmu_internal.h @@ -168,7 +168,7 @@ void disallowed_hugepage_adjust(struct kvm_page_fault *fault, u64 spte, int cur_ void *mmu_memory_cache_alloc(struct kvm_mmu_memory_cache *mc); -void account_huge_nx_page(struct kvm *kvm, struct kvm_mmu_page *sp); +void __account_huge_nx_page(struct kvm *kvm, struct kvm_mmu_page *sp); void unaccount_huge_nx_page(struct kvm *kvm, struct kvm_mmu_page *sp); #endif /* __KVM_X86_MMU_INTERNAL_H */ diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c index b3b6426725d4..f05423545e6d 100644 --- a/arch/x86/kvm/mmu/tdp_mmu.c +++ b/arch/x86/kvm/mmu/tdp_mmu.c @@ -1122,16 +1122,13 @@ static int tdp_mmu_map_handle_target_level(struct kvm_vcpu *vcpu, * @kvm: kvm instance * @iter: a tdp_iter instance currently on the SPTE that should be set * @sp: The new TDP page table to install. - * @account_nx: True if this page table is being installed to split a - * non-executable huge page. * @shared: This operation is running under the MMU lock in read mode. * * Returns: 0 if the new page table was installed. Non-0 if the page table * could not be installed (e.g. the atomic compare-exchange failed). */ static int tdp_mmu_link_sp(struct kvm *kvm, struct tdp_iter *iter, - struct kvm_mmu_page *sp, bool account_nx, - bool shared) + struct kvm_mmu_page *sp, bool shared) { u64 spte = make_nonleaf_spte(sp->spt, !shadow_accessed_mask); int ret = 0; @@ -1146,8 +1143,6 @@ static int tdp_mmu_link_sp(struct kvm *kvm, struct tdp_iter *iter, spin_lock(&kvm->arch.tdp_mmu_pages_lock); list_add(&sp->link, &kvm->arch.tdp_mmu_pages); - if (account_nx) - account_huge_nx_page(kvm, sp); spin_unlock(&kvm->arch.tdp_mmu_pages_lock); return 0; @@ -1160,6 +1155,7 @@ static int tdp_mmu_link_sp(struct kvm *kvm, struct tdp_iter *iter, int kvm_tdp_mmu_map(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault) { struct kvm_mmu *mmu = vcpu->arch.mmu; + struct kvm *kvm = vcpu->kvm; struct tdp_iter iter; struct kvm_mmu_page *sp; int ret; @@ -1210,10 +1206,18 @@ int kvm_tdp_mmu_map(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault) sp = tdp_mmu_alloc_sp(vcpu); tdp_mmu_init_child_sp(sp, &iter); - if (tdp_mmu_link_sp(vcpu->kvm, &iter, sp, account_nx, true)) { + sp->lpage_disallowed = account_nx; + + if (tdp_mmu_link_sp(kvm, &iter, sp, true)) { tdp_mmu_free_sp(sp); break; } + + if (account_nx) { + spin_lock(&kvm->arch.tdp_mmu_pages_lock); + __account_huge_nx_page(kvm, sp); + spin_unlock(&kvm->arch.tdp_mmu_pages_lock); + } } } @@ -1501,7 +1505,7 @@ static int tdp_mmu_split_huge_page(struct kvm *kvm, struct tdp_iter *iter, * correctness standpoint since the translation will be the same either * way. */ - ret = tdp_mmu_link_sp(kvm, iter, sp, false, shared); + ret = tdp_mmu_link_sp(kvm, iter, sp, shared); if (ret) goto out; base-commit: 19164ad08bf668bca4f4bfbaacaa0a47c1b737a6 -- 2.35.1.1021.g381101b075-goog