Re: [PATCH v3 1/4] KVM: SVM: Inject #GP on guest MSR_TSC_AUX accesses if RDTSCP unsupported

Vitaly Kuznetsov
2021-04-26T08:49:24Z

Sean Christopherson <seanjc@google.com> writes:

> Inject #GP on guest accesses to MSR_TSC_AUX if RDTSCP is unsupported in
> the guest's CPUID model.
>
> Fixes: 46896c73c1a4 ("KVM: svm: add support for RDTSCP")
> Cc: stable@vger.kernel.org
> Signed-off-by: Sean Christopherson <seanjc@google.com>
> ---
> arch/x86/kvm/svm/svm.c | 7 +++++++
> 1 file changed, 7 insertions(+)
>
> diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
> index cd8c333ed2dc..9ed9c7bd7cfd 100644
> --- a/arch/x86/kvm/svm/svm.c
> +++ b/arch/x86/kvm/svm/svm.c
> @@ -2674,6 +2674,9 @@ static int svm_get_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
> case MSR_TSC_AUX:
> if (!boot_cpu_has(X86_FEATURE_RDTSCP))
> return 1;
> + if (!msr_info->host_initiated &&
> + !guest_cpuid_has(vcpu, X86_FEATURE_RDTSCP))
> + return 1;

Super-nit: a blank like before and after the condition would make this
consistent with the hunk you add to svm_set_msr() below.

> msr_info->data = svm->tsc_aux;
> break;
> /*
> @@ -2892,6 +2895,10 @@ static int svm_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr)
> if (!boot_cpu_has(X86_FEATURE_RDTSCP))
> return 1;
>
> + if (!msr->host_initiated &&
> + !guest_cpuid_has(vcpu, X86_FEATURE_RDTSCP))
> + return 1;
> +
> /*
> * This is rare, so we update the MSR here instead of using
> * direct_access_msrs. Doing that would require a rdmsr in

Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>

--
Vitaly