Messages in this thread Patch in this message | | | Date | Thu, 9 Dec 2021 19:49:18 +0100 | Subject | Re: [PATCH v2 1/6] KVM: x86/pmu: Setup pmc->eventsel for fixed PMCs | From | Paolo Bonzini <> |
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On 12/6/21 20:57, Jim Mattson wrote: >> + >> + for (i = 0; i < pmu->nr_arch_fixed_counters; i++) { >> + pmc = &pmu->fixed_counters[i]; >> + event = fixed_pmc_events[array_index_nospec(i, size)]; > How do we know that i < size? For example, Ice Lake supports 4 fixed > counters, but fixed_pmc_events only has three entries.
We don't, and it's a preexisting bug in intel_pmu_refresh. Either we hack around it like
diff --git a/arch/x86/kvm/vmx/pmu_intel.c b/arch/x86/kvm/vmx/pmu_intel.c index 1b7456b2177b..6f03c8bf1bc2 100644 --- a/arch/x86/kvm/vmx/pmu_intel.c +++ b/arch/x86/kvm/vmx/pmu_intel.c @@ -500,8 +500,9 @@ static void intel_pmu_refresh(struct kvm_vcpu *vcpu) pmu->nr_arch_fixed_counters = 0; } else { pmu->nr_arch_fixed_counters = - min_t(int, edx.split.num_counters_fixed, - x86_pmu.num_counters_fixed); + min3(ARRAY_SIZE(fixed_pmc_events), + (size_t) edx.split.num_counters_fixed, + (size_t) x86_pmu.num_counters_fixed); edx.split.bit_width_fixed = min_t(int, edx.split.bit_width_fixed, x86_pmu.bit_width_fixed); pmu->counter_bitmask[KVM_PMC_FIXED] = or we modify find_fixed_event and its caller to support PERF_TYPE_RAW counters, and then add support for the IceLake TOPDOWN.SLOTS fixed counter.
What's your preference?
Paolo
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