| From | Jim Mattson <> | Date | Tue, 4 May 2021 14:45:47 -0700 | Subject | Re: [PATCH 03/15] KVM: SVM: Inject #UD on RDTSCP when it should be disabled in the guest |
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On Tue, May 4, 2021 at 10:17 AM Sean Christopherson <seanjc@google.com> wrote: > > Intercept RDTSCP to inject #UD if RDTSC is disabled in the guest. > > Note, SVM does not support intercepting RDPID. Unlike VMX's > ENABLE_RDTSCP control, RDTSCP interception does not apply to RDPID. This > is a benign virtualization hole as the host kernel (incorrectly) sets > MSR_TSC_AUX if RDTSCP is supported, and KVM loads the guest's MSR_TSC_AUX > into hardware if RDTSCP is supported in the host, i.e. KVM will not leak > the host's MSR_TSC_AUX to the guest. > > But, when the kernel bug is fixed, KVM will start leaking the host's > MSR_TSC_AUX if RDPID is supported in hardware, but RDTSCP isn't available > for whatever reason. This leak will be remedied in a future commit. > > Fixes: 46896c73c1a4 ("KVM: svm: add support for RDTSCP") > Cc: stable@vger.kernel.org > Signed-off-by: Sean Christopherson <seanjc@google.com> > --- ... > @@ -4007,8 +4017,7 @@ static void svm_vcpu_after_set_cpuid(struct kvm_vcpu *vcpu) > svm->nrips_enabled = kvm_cpu_cap_has(X86_FEATURE_NRIPS) && > guest_cpuid_has(vcpu, X86_FEATURE_NRIPS); > > - /* Check again if INVPCID interception if required */ > - svm_check_invpcid(svm); > + svm_recalc_instruction_intercepts(vcpu, svm);
Does the right thing happen here if the vCPU is in guest mode when userspace decides to toggle the CPUID.80000001H:EDX.RDTSCP bit on or off?
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