Re: [PATCH v7 17/17] KVM: selftests: Add svm_pmu_host_guest_test for Host-Only/Guest-Only bits

[Jim Mattson]

On Thu, May 28, 2026 at 11:04 AM Sean Christopherson <seanjc@xxxxxxxxxx> wrote:
>
> On Thu, May 28, 2026, Yosry Ahmed wrote:
> > On Wed, May 27, 2026 at 7:25 PM Sean Christopherson <seanjc@xxxxxxxxxx> wrote:
> > >
> > > On Wed, May 27, 2026, Yosry Ahmed wrote:
> > > > +int main(int argc, char *argv[])
> > > > +{
> > > > +     struct kvm_pmu_event_filter *filter;
> > > > +     struct kvm_vcpu *vcpu;
> > > > +     struct kvm_vm *vm;
> > > > +     struct ucall uc;
> > > > +     gva_t svm_gva;
> > > > +
> > > > +     TEST_REQUIRE(kvm_cpu_has(X86_FEATURE_SVM));
> > > > +     TEST_REQUIRE(kvm_is_pmu_enabled());
> > > > +     TEST_REQUIRE(get_kvm_amd_param_bool("enable_mediated_pmu"));
> > >
> > > This can and should be handled in a helper, using either host_cpu_is_intel or
> > > host_cpu_is_amd_compatible to choose while vendor to query.
> > >
> > > > +     TEST_REQUIRE(host_cpu_is_amd && kvm_cpu_family() >= 0x17);
> > >
> > > Why the family check?  Actually, why check host_cpu_is_amd at all?
> >
> > I assume you mean that we don't need host_cpu_is_amd because we
> > require X86_FEATURE_SVM above?
>
> Yes.
>
> > Unless H/G emulation doesn't really work for cross-vendor emulation? I
> > honestly don't know.
>
> Not just cross-vendor emulation, KVM and selftests also support Hygon CPUs.
>
> > I will defer to Jim for the family check, I took this as-is. My guess
> > is that maybe older families did not support H/G bits or some of the
> > other PMU features used by the test.
>
> If that's true, then the mediated PMU shouldn't be enabled.  If the mediated PMU
> _can_ be enabled for CPUs that do _and_ don't support H/G bits, then we need to
> figure out a way to enumerate H/G support to userspace.  Because telling userspace
> to check F/M/S ain't going to fly.

The test counts AMD_ZEN_INSTRUCTIONS_RETIRED, so I tested for
"Zen."This is admittedly pedantic, as I don't think AMD has ever
changed this event code. Blame AMD for not having any architected
events. :)