diff options
| -rw-r--r-- | arch/x86/kvm/mmu/mmu.c | 8 | ||||
| -rw-r--r-- | arch/x86/kvm/vmx/vmx.c | 10 |
2 files changed, 11 insertions, 7 deletions
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index 561e7c29cf9e..77ca81e13722 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -4616,14 +4616,16 @@ out_unlock: bool kvm_mmu_may_ignore_guest_pat(void) { /* - * When EPT is enabled (shadow_memtype_mask is non-zero), and the VM + * When EPT is enabled (shadow_memtype_mask is non-zero), the CPU does + * not support self-snoop (or is affected by an erratum), and the VM * has non-coherent DMA (DMA doesn't snoop CPU caches), KVM's ABI is to * honor the memtype from the guest's PAT so that guest accesses to * memory that is DMA'd aren't cached against the guest's wishes. As a * result, KVM _may_ ignore guest PAT, whereas without non-coherent DMA, - * KVM _always_ ignores guest PAT (when EPT is enabled). + * KVM _always_ ignores or honors guest PAT, i.e. doesn't toggle SPTE + * bits in response to non-coherent device (un)registration. */ - return shadow_memtype_mask; + return !static_cpu_has(X86_FEATURE_SELFSNOOP) && shadow_memtype_mask; } int kvm_tdp_page_fault(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault) diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index a3cc0bc30540..e97e1ad79bf4 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -7667,11 +7667,13 @@ u8 vmx_get_mt_mask(struct kvm_vcpu *vcpu, gfn_t gfn, bool is_mmio) /* * Force WB and ignore guest PAT if the VM does NOT have a non-coherent - * device attached. Letting the guest control memory types on Intel - * CPUs may result in unexpected behavior, and so KVM's ABI is to trust - * the guest to behave only as a last resort. + * device attached and the CPU doesn't support self-snoop. Letting the + * guest control memory types on Intel CPUs without self-snoop may + * result in unexpected behavior, and so KVM's (historical) ABI is to + * trust the guest to behave only as a last resort. */ - if (!kvm_arch_has_noncoherent_dma(vcpu->kvm)) + if (!static_cpu_has(X86_FEATURE_SELFSNOOP) && + !kvm_arch_has_noncoherent_dma(vcpu->kvm)) return (MTRR_TYPE_WRBACK << VMX_EPT_MT_EPTE_SHIFT) | VMX_EPT_IPAT_BIT; return (MTRR_TYPE_WRBACK << VMX_EPT_MT_EPTE_SHIFT); |