Userspace that does not know about the AMD_IBRS bit might still allow the guest to protect itself with MSR_IA32_SPEC_CTRL using the Intel SPEC_CTRL bit. However, svm.c disallows this and will cause a #GP in the guest when writing to the MSR. Fix this by loosening the test and allowing the Intel CPUID bit, and in fact allow the AMD_STIBP bit as well since it allows writing to MSR_IA32_SPEC_CTRL too. Reported-by: Zhiyi Guo <zhguo@xxxxxxxxxx> Analyzed-by: Dr. David Alan Gilbert <dgilbert@xxxxxxxxxx> Analyzed-by: Laszlo Ersek <lersek@xxxxxxxxxx> Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx> --- arch/x86/kvm/svm.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c index bf0556588ad0..a3e32d61d60c 100644 --- a/arch/x86/kvm/svm.c +++ b/arch/x86/kvm/svm.c @@ -4225,6 +4225,8 @@ 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)) return 1; @@ -4310,6 +4312,8 @@ 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)) return 1; -- 1.8.3.1
