diff options
Diffstat (limited to 'arch/x86/kvm/vmx/vmx.c')
| -rw-r--r-- | arch/x86/kvm/vmx/vmx.c | 51 |
1 files changed, 41 insertions, 10 deletions
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index cea8c07f5229..fe5615fd8295 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -858,7 +858,7 @@ unsigned int __vmx_vcpu_run_flags(struct vcpu_vmx *vmx) * to change it directly without causing a vmexit. In that case read * it after vmexit and store it in vmx->spec_ctrl. */ - if (unlikely(!msr_write_intercepted(vmx, MSR_IA32_SPEC_CTRL))) + if (!msr_write_intercepted(vmx, MSR_IA32_SPEC_CTRL)) flags |= VMX_RUN_SAVE_SPEC_CTRL; return flags; @@ -1348,8 +1348,10 @@ void vmx_vcpu_load_vmcs(struct kvm_vcpu *vcpu, int cpu, /* * No indirect branch prediction barrier needed when switching - * the active VMCS within a guest, e.g. on nested VM-Enter. - * The L1 VMM can protect itself with retpolines, IBPB or IBRS. + * the active VMCS within a vCPU, unless IBRS is advertised to + * the vCPU. To minimize the number of IBPBs executed, KVM + * performs IBPB on nested VM-Exit (a single nested transition + * may switch the active VMCS multiple times). */ if (!buddy || WARN_ON_ONCE(buddy->vmcs != prev)) indirect_branch_prediction_barrier(); @@ -1834,12 +1836,42 @@ bool nested_vmx_allowed(struct kvm_vcpu *vcpu) return nested && guest_cpuid_has(vcpu, X86_FEATURE_VMX); } -static inline bool vmx_feature_control_msr_valid(struct kvm_vcpu *vcpu, - uint64_t val) +/* + * Userspace is allowed to set any supported IA32_FEATURE_CONTROL regardless of + * guest CPUID. Note, KVM allows userspace to set "VMX in SMX" to maintain + * backwards compatibility even though KVM doesn't support emulating SMX. And + * because userspace set "VMX in SMX", the guest must also be allowed to set it, + * e.g. if the MSR is left unlocked and the guest does a RMW operation. + */ +#define KVM_SUPPORTED_FEATURE_CONTROL (FEAT_CTL_LOCKED | \ + FEAT_CTL_VMX_ENABLED_INSIDE_SMX | \ + FEAT_CTL_VMX_ENABLED_OUTSIDE_SMX | \ + FEAT_CTL_SGX_LC_ENABLED | \ + FEAT_CTL_SGX_ENABLED | \ + FEAT_CTL_LMCE_ENABLED) + +static inline bool is_vmx_feature_control_msr_valid(struct vcpu_vmx *vmx, + struct msr_data *msr) { - uint64_t valid_bits = to_vmx(vcpu)->msr_ia32_feature_control_valid_bits; + uint64_t valid_bits; + + /* + * Ensure KVM_SUPPORTED_FEATURE_CONTROL is updated when new bits are + * exposed to the guest. + */ + WARN_ON_ONCE(vmx->msr_ia32_feature_control_valid_bits & + ~KVM_SUPPORTED_FEATURE_CONTROL); - return !(val & ~valid_bits); + if (!msr->host_initiated && + (vmx->msr_ia32_feature_control & FEAT_CTL_LOCKED)) + return false; + + if (msr->host_initiated) + valid_bits = KVM_SUPPORTED_FEATURE_CONTROL; + else + valid_bits = vmx->msr_ia32_feature_control_valid_bits; + + return !(msr->data & ~valid_bits); } static int vmx_get_msr_feature(struct kvm_msr_entry *msr) @@ -2238,10 +2270,9 @@ static int vmx_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info) vcpu->arch.mcg_ext_ctl = data; break; case MSR_IA32_FEAT_CTL: - if (!vmx_feature_control_msr_valid(vcpu, data) || - (to_vmx(vcpu)->msr_ia32_feature_control & - FEAT_CTL_LOCKED && !msr_info->host_initiated)) + if (!is_vmx_feature_control_msr_valid(vmx, msr_info)) return 1; + vmx->msr_ia32_feature_control = data; if (msr_info->host_initiated && data == 0) vmx_leave_nested(vcpu); |