Re: [PATCH v9] arm/kvm: Enable support for KVM_ARM_VCPU_PMU_V3_FILTER

[Thomas Huth]

On 09/04/2024 09.47, Shaoqin Huang wrote:
> Hi Thmoas,
>
> On 4/9/24 13:33, Thomas Huth wrote:
> > > +        assert_has_feature(qts, "host", "kvm-pmu-filter");
> >
> > So you assert here that the feature is available ...
> >
> > >           assert_has_feature(qts, "host", "kvm-steal-time");
> > >           assert_has_feature(qts, "host", "sve");
> > >           resp = do_query_no_props(qts, "host");
> > > +        kvm_supports_pmu_filter = resp_get_feature_str(resp, 
> > > "kvm-pmu-filter");
> > >           kvm_supports_steal_time = resp_get_feature(resp, 
> > > "kvm-steal-time");
> > >           kvm_supports_sve = resp_get_feature(resp, "sve");
> > >           vls = resp_get_sve_vls(resp);
> > >           qobject_unref(resp);
> > > +        if (kvm_supports_pmu_filter) { >
> > ... why do you then need to check for its availability here again?
> > I either don't understand this part of the code, or you could drop the 
> > kvm_supports_pmu_filter variable and simply always execute the code below.
>
> Thanks for your reviewing. I did so because all other feature like 
> "kvm-steal-time" check its availability again. I don't know the original 
> reason why they did that. I just followed it.
>
> Do you think we should delete all the checking?

resp_get_feature() seems to return a boolean value, so though these feature 
could be there, they still could be disabled, I assume? Thus we likely need 
to keep the check for those.

 Thomas