diff options
Diffstat (limited to 'arch/x86/kvm/vmx/vmx.c')
| -rw-r--r-- | arch/x86/kvm/vmx/vmx.c | 40 |
1 files changed, 13 insertions, 27 deletions
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index bedb9ba96918..13a6b0281e37 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -7670,39 +7670,25 @@ int vmx_vm_init(struct kvm *kvm) u8 vmx_get_mt_mask(struct kvm_vcpu *vcpu, gfn_t gfn, bool is_mmio) { - /* We wanted to honor guest CD/MTRR/PAT, but doing so could result in - * memory aliases with conflicting memory types and sometimes MCEs. - * We have to be careful as to what are honored and when. - * - * For MMIO, guest CD/MTRR are ignored. The EPT memory type is set to - * UC. The effective memory type is UC or WC depending on guest PAT. - * This was historically the source of MCEs and we want to be - * conservative. - * - * When there is no need to deal with noncoherent DMA (e.g., no VT-d - * or VT-d has snoop control), guest CD/MTRR/PAT are all ignored. The - * EPT memory type is set to WB. The effective memory type is forced - * WB. - * - * Otherwise, we trust guest. Guest CD/MTRR/PAT are all honored. The - * EPT memory type is used to emulate guest CD/MTRR. + /* + * Force UC for host MMIO regions, as allowing the guest to access MMIO + * with cacheable accesses will result in Machine Checks. */ - if (is_mmio) return MTRR_TYPE_UNCACHABLE << VMX_EPT_MT_EPTE_SHIFT; - if (!kvm_arch_has_noncoherent_dma(vcpu->kvm)) + /* + * Force WB and ignore guest PAT if the VM does NOT have a non-coherent + * 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 (!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; - if (kvm_read_cr0_bits(vcpu, X86_CR0_CD)) { - if (kvm_check_has_quirk(vcpu->kvm, KVM_X86_QUIRK_CD_NW_CLEARED)) - return MTRR_TYPE_WRBACK << VMX_EPT_MT_EPTE_SHIFT; - else - return (MTRR_TYPE_UNCACHABLE << VMX_EPT_MT_EPTE_SHIFT) | - VMX_EPT_IPAT_BIT; - } - - return kvm_mtrr_get_guest_memory_type(vcpu, gfn) << VMX_EPT_MT_EPTE_SHIFT; + return (MTRR_TYPE_WRBACK << VMX_EPT_MT_EPTE_SHIFT); } static void vmcs_set_secondary_exec_control(struct vcpu_vmx *vmx, u32 new_ctl) |