Re: [PATCH v7 10/19] KVM: selftests: Test Intel PMU architectural events on fixed counters

[Sean Christopherson]

On Tue, Nov 07, 2023, Sean Christopherson wrote:
> @@ -199,6 +219,22 @@ static void guest_test_arch_event(uint8_t idx)
>  		__guest_test_arch_event(idx, gp_event, i, base_pmc_msr + i,
>  					MSR_P6_EVNTSEL0 + i, eventsel);
>  	}
> +
> +	if (!guest_has_perf_global_ctrl)
> +		return;
> +
> +	fixed_event = intel_event_to_feature[idx].fixed_event;
> +	if (pmu_is_null_feature(fixed_event) || !this_pmu_has(fixed_event))
> +		return;
> +
> +	i = fixed_event.f.bit;
> +
> +	wrmsr(MSR_CORE_PERF_FIXED_CTR_CTRL, FIXED_PMC_CTRL(i, FIXED_PMC_KERNEL));
> +
> +	__guest_test_arch_event(idx, fixed_event, FIXED_PMC_RDPMC_BASE + i,

Grr, this should be an OR, not a SUM, i.e. "FIXED_PMC_RDPMC_BASE | i".  That's
how Like/Jinrong originally had things, but I got confused by the BASE terminology
and "fixed" it.  The end result is the name, but the PMU code is hard enough to
follow as it is.

I'm also going to rename FIXED_PMC_RDPMC_BASE, that is a terrible name that got
copy+pasted from perf.  It's not a base value, it's a single flag that says "read
fixed counters".