linux-kernel - Re: [PATCH 3/4] KVM: x86/pmu: Reuse find_perf_hw_id() and drop find_fixed

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

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

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,