From ccf31d6e6cc53e50cc42845061174082fd229c79 Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Tue, 15 Aug 2023 13:36:40 -0700 Subject: [PATCH] KVM: x86/mmu: Use KVM-governed feature framework to track "GBPAGES enabled" Use the governed feature framework to track whether or not the guest can use 1GiB pages, and drop the one-off helper that wraps the surprisingly non-trivial logic surrounding 1GiB page usage in the guest. No functional change intended. Reviewed-by: Yuan Yao Link: https://lore.kernel.org/r/20230815203653.519297-3-seanjc@google.com Signed-off-by: Sean Christopherson --- arch/x86/kvm/cpuid.c | 17 +++++++++++++++++ arch/x86/kvm/governed_features.h | 2 ++ arch/x86/kvm/mmu/mmu.c | 20 +++----------------- 3 files changed, 22 insertions(+), 17 deletions(-) diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c index 4ba43ae..67e9f79 100644 --- a/arch/x86/kvm/cpuid.c +++ b/arch/x86/kvm/cpuid.c @@ -312,11 +312,28 @@ static void kvm_vcpu_after_set_cpuid(struct kvm_vcpu *vcpu) { struct kvm_lapic *apic = vcpu->arch.apic; struct kvm_cpuid_entry2 *best; + bool allow_gbpages; BUILD_BUG_ON(KVM_NR_GOVERNED_FEATURES > KVM_MAX_NR_GOVERNED_FEATURES); bitmap_zero(vcpu->arch.governed_features.enabled, KVM_MAX_NR_GOVERNED_FEATURES); + /* + * If TDP is enabled, let the guest use GBPAGES if they're supported in + * hardware. The hardware page walker doesn't let KVM disable GBPAGES, + * i.e. won't treat them as reserved, and KVM doesn't redo the GVA->GPA + * walk for performance and complexity reasons. Not to mention KVM + * _can't_ solve the problem because GVA->GPA walks aren't visible to + * KVM once a TDP translation is installed. Mimic hardware behavior so + * that KVM's is at least consistent, i.e. doesn't randomly inject #PF. + * If TDP is disabled, honor *only* guest CPUID as KVM has full control + * and can install smaller shadow pages if the host lacks 1GiB support. + */ + allow_gbpages = tdp_enabled ? boot_cpu_has(X86_FEATURE_GBPAGES) : + guest_cpuid_has(vcpu, X86_FEATURE_GBPAGES); + if (allow_gbpages) + kvm_governed_feature_set(vcpu, X86_FEATURE_GBPAGES); + best = kvm_find_cpuid_entry(vcpu, 1); if (best && apic) { if (cpuid_entry_has(best, X86_FEATURE_TSC_DEADLINE_TIMER)) diff --git a/arch/x86/kvm/governed_features.h b/arch/x86/kvm/governed_features.h index 40ce8e6..b29c15d 100644 --- a/arch/x86/kvm/governed_features.h +++ b/arch/x86/kvm/governed_features.h @@ -5,5 +5,7 @@ BUILD_BUG() #define KVM_GOVERNED_X86_FEATURE(x) KVM_GOVERNED_FEATURE(X86_FEATURE_##x) +KVM_GOVERNED_X86_FEATURE(GBPAGES) + #undef KVM_GOVERNED_X86_FEATURE #undef KVM_GOVERNED_FEATURE diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index 31d9cbe..a0c2acb 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -4808,28 +4808,13 @@ static void __reset_rsvds_bits_mask(struct rsvd_bits_validate *rsvd_check, } } -static bool guest_can_use_gbpages(struct kvm_vcpu *vcpu) -{ - /* - * If TDP is enabled, let the guest use GBPAGES if they're supported in - * hardware. The hardware page walker doesn't let KVM disable GBPAGES, - * i.e. won't treat them as reserved, and KVM doesn't redo the GVA->GPA - * walk for performance and complexity reasons. Not to mention KVM - * _can't_ solve the problem because GVA->GPA walks aren't visible to - * KVM once a TDP translation is installed. Mimic hardware behavior so - * that KVM's is at least consistent, i.e. doesn't randomly inject #PF. - */ - return tdp_enabled ? boot_cpu_has(X86_FEATURE_GBPAGES) : - guest_cpuid_has(vcpu, X86_FEATURE_GBPAGES); -} - static void reset_guest_rsvds_bits_mask(struct kvm_vcpu *vcpu, struct kvm_mmu *context) { __reset_rsvds_bits_mask(&context->guest_rsvd_check, vcpu->arch.reserved_gpa_bits, context->cpu_role.base.level, is_efer_nx(context), - guest_can_use_gbpages(vcpu), + guest_can_use(vcpu, X86_FEATURE_GBPAGES), is_cr4_pse(context), guest_cpuid_is_amd_or_hygon(vcpu)); } @@ -4906,7 +4891,8 @@ static void reset_shadow_zero_bits_mask(struct kvm_vcpu *vcpu, __reset_rsvds_bits_mask(shadow_zero_check, reserved_hpa_bits(), context->root_role.level, context->root_role.efer_nx, - guest_can_use_gbpages(vcpu), is_pse, is_amd); + guest_can_use(vcpu, X86_FEATURE_GBPAGES), + is_pse, is_amd); if (!shadow_me_mask) return; -- 2.7.4