Re: [PATCH 1/2] KVM: SVM: Fix TSC_AUX virtualization setup

[Tom Lendacky]

On 9/14/23 15:48, Tom Lendacky wrote:
> On 9/14/23 15:28, Sean Christopherson wrote:
> > On Thu, Sep 14, 2023, Tom Lendacky wrote:

> > > +        if (guest_cpuid_has(vcpu, X86_FEATURE_RDTSCP))
> > > +            svm_clr_intercept(svm, INTERCEPT_RDTSCP);
> >
> > Same thing here.
>
> Will do.

For RDTSCP, svm_recalc_instruction_intercepts() will set/clear the RDTSCP 
intercept as part of the svm_vcpu_set_after_cpuid() path, but it will only 
do it based on kvm_cpu_cap_has(X86_FEATURE_RDTSCP) being true, which is 
very likely.

Do you think that is good enough and we can drop the setting and clearing 
of the RDTSCP intercept in the sev_es_vcpu_set_after_cpuid() function and 
only deal with the TSC_AUX MSR intercept?

On a side note, it looks like RDTSCP would not be intercepted if the KVM 
cap X86_FEATURE_RDTSCP feature is cleared, however unlikely, in 
kvm_set_cpu_caps() and RDTSCP is not advertised to the guest (assuming the 
guest is ignoring the RDTSCP CPUID bit).

Thanks,
Tom

> Thanks,
> Tom
>
> > > +    }
> > > +}