Re: [PATCH 3/4] KVM: x86/pmu: Reuse find_perf_hw_id() and drop find_fixed_event()

[Paolo Bonzini]

On 11/16/21 13:20, Like Xu wrote:
> +static inline unsigned int intel_find_fixed_event(int idx)
> +{
> +	u32 event;
> +	size_t size = ARRAY_SIZE(fixed_pmc_events);
> +
> +	if (idx >= size)
> +		return PERF_COUNT_HW_MAX;
> +
> +	event = fixed_pmc_events[array_index_nospec(idx, size)];
> +	return intel_arch_events[event].event_type;
> +}
> +
> +
>   static unsigned int intel_find_perf_hw_id(struct kvm_pmc *pmc)
>   {
>   	struct kvm_pmu *pmu = pmc_to_pmu(pmc);
> @@ -75,6 +88,9 @@ static unsigned int intel_find_perf_hw_id(struct kvm_pmc *pmc)
>   	u8 unit_mask = (pmc->eventsel & ARCH_PERFMON_EVENTSEL_UMASK) >> 8;
>   	int i;
>   
> +	if (pmc_is_fixed(pmc))
> +		return intel_find_fixed_event(pmc->idx - INTEL_PMC_IDX_FIXED);

Is intel_find_fixed_event needed at all?  As you point out in the commit
message, eventsel/unit_mask are valid so you can do

@@ -88,13 +75,11 @@ static unsigned int intel_pmc_perf_hw_id(struct kvm_pmc *pmc)
 	u8 unit_mask = (pmc->eventsel & ARCH_PERFMON_EVENTSEL_UMASK) >> 8;
 	int i;
 
-	if (pmc_is_fixed(pmc))
-		return intel_find_fixed_event(pmc->idx - INTEL_PMC_IDX_FIXED);
-
 	for (i = 0; i < ARRAY_SIZE(intel_arch_events); i++)
 		if (intel_arch_events[i].eventsel == event_select
 		    && intel_arch_events[i].unit_mask == unit_mask
-		    && (pmu->available_event_types & (1 << i)))
+		    && (pmc_is_fixed(pmc) ||
+			pmu->available_event_types & (1 << i)))
 			break;
 
 	if (i == ARRAY_SIZE(intel_arch_events))

What do you think?  It's less efficient but makes fixed/gp more similar.

Can you please resubmit the series based on the review feedback?

Thanks,