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From: Paolo Bonzini <pbonzini@redhat.com>
To: Like Xu <like.xu.linux@gmail.com>, Jim Mattson <jmattson@google.com>
Cc: Sean Christopherson <seanjc@google.com>,
	Vitaly Kuznetsov <vkuznets@redhat.com>,
	Wanpeng Li <wanpengli@tencent.com>,
	Joerg Roedel <joro@8bytes.org>,
	kvm@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 3/4] KVM: x86/pmu: Reuse find_perf_hw_id() and drop find_fixed_event()
Date: Thu, 18 Nov 2021 16:00:03 +0100	[thread overview]
Message-ID: <85286356-8005-8a4d-927c-c3d70c723161@redhat.com> (raw)
In-Reply-To: <20211116122030.4698-4-likexu@tencent.com>

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,


  parent reply	other threads:[~2021-11-18 15:00 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-11-16 12:20 [PATCH 0/4] KVM: x86/pmu: An insightful refactoring of vPMU code Like Xu
2021-11-16 12:20 ` [PATCH 1/4] KVM: x86/pmu: Setup pmc->eventsel for fixed PMCs Like Xu
2021-11-16 12:20 ` [PATCH 2/4] KVM: x86/pmu: Refactoring find_arch_event() to find_perf_hw_id() Like Xu
2021-11-18 13:29   ` Paolo Bonzini
2021-11-16 12:20 ` [PATCH 3/4] KVM: x86/pmu: Reuse find_perf_hw_id() and drop find_fixed_event() Like Xu
2021-11-18 14:43   ` Paolo Bonzini
2021-11-18 15:00   ` Paolo Bonzini [this message]
2021-11-19  7:16     ` Like Xu
2021-11-19 10:29       ` Paolo Bonzini
2021-11-19 11:10         ` Like Xu
2021-11-16 12:20 ` [PATCH 4/4] KVM: x86/pmu: Refactoring kvm_perf_overflow{_intr}() Like Xu
2021-11-18 14:53   ` Paolo Bonzini

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