From 7cb6087b45367aa2edf7f026a3144031ce4dc75a Mon Sep 17 00:00:00 2001 From: Paolo Bonzini Date: Thu, 3 Dec 2020 09:40:15 -0500 Subject: [PATCH] KVM: x86: reinstate vendor-agnostic check on SPEC_CTRL cpuid bits [ Upstream commit 39485ed95d6b83b62fa75c06c2c4d33992e0d971 ] Until commit e7c587da1252 ("x86/speculation: Use synthetic bits for IBRS/IBPB/STIBP"), KVM was testing both Intel and AMD CPUID bits before allowing the guest to write MSR_IA32_SPEC_CTRL and MSR_IA32_PRED_CMD. Testing only Intel bits on VMX processors, or only AMD bits on SVM processors, fails if the guests are created with the "opposite" vendor as the host. While at it, also tweak the host CPU check to use the vendor-agnostic feature bit X86_FEATURE_IBPB, since we only care about the availability of the MSR on the host here and not about specific CPUID bits. Fixes: e7c587da1252 ("x86/speculation: Use synthetic bits for IBRS/IBPB/STIBP") Cc: stable@vger.kernel.org Reported-by: Denis V. Lunev Signed-off-by: Paolo Bonzini Signed-off-by: Sasha Levin --- arch/x86/kvm/cpuid.h | 14 ++++++++++++++ arch/x86/kvm/svm.c | 14 ++++---------- arch/x86/kvm/vmx/vmx.c | 8 ++++---- 3 files changed, 22 insertions(+), 14 deletions(-) diff --git a/arch/x86/kvm/cpuid.h b/arch/x86/kvm/cpuid.h index d78a61408243..7dec43b2c420 100644 --- a/arch/x86/kvm/cpuid.h +++ b/arch/x86/kvm/cpuid.h @@ -154,6 +154,20 @@ static inline int guest_cpuid_stepping(struct kvm_vcpu *vcpu) return x86_stepping(best->eax); } +static inline bool guest_has_spec_ctrl_msr(struct kvm_vcpu *vcpu) +{ + return (guest_cpuid_has(vcpu, X86_FEATURE_SPEC_CTRL) || + guest_cpuid_has(vcpu, X86_FEATURE_AMD_STIBP) || + guest_cpuid_has(vcpu, X86_FEATURE_AMD_IBRS) || + guest_cpuid_has(vcpu, X86_FEATURE_AMD_SSBD)); +} + +static inline bool guest_has_pred_cmd_msr(struct kvm_vcpu *vcpu) +{ + return (guest_cpuid_has(vcpu, X86_FEATURE_SPEC_CTRL) || + guest_cpuid_has(vcpu, X86_FEATURE_AMD_IBPB)); +} + static inline bool supports_cpuid_fault(struct kvm_vcpu *vcpu) { return vcpu->arch.msr_platform_info & MSR_PLATFORM_INFO_CPUID_FAULT; diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c index ca746006ac04..2b506904be02 100644 --- a/arch/x86/kvm/svm.c +++ b/arch/x86/kvm/svm.c @@ -4233,10 +4233,7 @@ static int svm_get_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info) break; case MSR_IA32_SPEC_CTRL: if (!msr_info->host_initiated && - !guest_cpuid_has(vcpu, X86_FEATURE_SPEC_CTRL) && - !guest_cpuid_has(vcpu, X86_FEATURE_AMD_STIBP) && - !guest_cpuid_has(vcpu, X86_FEATURE_AMD_IBRS) && - !guest_cpuid_has(vcpu, X86_FEATURE_AMD_SSBD)) + !guest_has_spec_ctrl_msr(vcpu)) return 1; msr_info->data = svm->spec_ctrl; @@ -4320,10 +4317,7 @@ static int svm_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr) break; case MSR_IA32_SPEC_CTRL: if (!msr->host_initiated && - !guest_cpuid_has(vcpu, X86_FEATURE_SPEC_CTRL) && - !guest_cpuid_has(vcpu, X86_FEATURE_AMD_STIBP) && - !guest_cpuid_has(vcpu, X86_FEATURE_AMD_IBRS) && - !guest_cpuid_has(vcpu, X86_FEATURE_AMD_SSBD)) + !guest_has_spec_ctrl_msr(vcpu)) return 1; if (data & ~kvm_spec_ctrl_valid_bits(vcpu)) @@ -4348,12 +4342,12 @@ static int svm_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr) break; case MSR_IA32_PRED_CMD: if (!msr->host_initiated && - !guest_cpuid_has(vcpu, X86_FEATURE_AMD_IBPB)) + !guest_has_pred_cmd_msr(vcpu)) return 1; if (data & ~PRED_CMD_IBPB) return 1; - if (!boot_cpu_has(X86_FEATURE_AMD_IBPB)) + if (!boot_cpu_has(X86_FEATURE_IBPB)) return 1; if (!data) break; diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index 8450fce70bd9..e7fd2f00edc1 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -1788,7 +1788,7 @@ static int vmx_get_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info) break; case MSR_IA32_SPEC_CTRL: if (!msr_info->host_initiated && - !guest_cpuid_has(vcpu, X86_FEATURE_SPEC_CTRL)) + !guest_has_spec_ctrl_msr(vcpu)) return 1; msr_info->data = to_vmx(vcpu)->spec_ctrl; @@ -1971,7 +1971,7 @@ static int vmx_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info) break; case MSR_IA32_SPEC_CTRL: if (!msr_info->host_initiated && - !guest_cpuid_has(vcpu, X86_FEATURE_SPEC_CTRL)) + !guest_has_spec_ctrl_msr(vcpu)) return 1; if (data & ~kvm_spec_ctrl_valid_bits(vcpu)) @@ -1999,12 +1999,12 @@ static int vmx_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info) break; case MSR_IA32_PRED_CMD: if (!msr_info->host_initiated && - !guest_cpuid_has(vcpu, X86_FEATURE_SPEC_CTRL)) + !guest_has_pred_cmd_msr(vcpu)) return 1; if (data & ~PRED_CMD_IBPB) return 1; - if (!boot_cpu_has(X86_FEATURE_SPEC_CTRL)) + if (!boot_cpu_has(X86_FEATURE_IBPB)) return 1; if (!data) break;