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charset="UTF-8" On Fri, Sep 18, 2026 at 12:39 PM Zide Chen wrote: > > + pmc = kvm_pmc_idx_to_pmc(pmu, INTEL_PMC_IDX_FIXED_SLOTS); > + if (pmc && intel_pmu_metrics_clear_enabled(pmu)) { If kvm_vcpu_has_perf_metrics() requires fixed counter 3 (see my reply to 5/12), pmc can't be NULL here. [...] > + if (perf_capabilities & PERF_CAP_RDPMC_METRICS_CLEAR) > + pmu->fixed_ctr_ctrl_rsvd &= > + ~intel_fixed_bits_by_idx(INTEL_FIXED_SLOTS_IDX, > + INTEL_FIXED_3_METRICS_CLEAR); This should be predicated on the guest actually having fixed counter 3 (and PERF_METRICS). intel_pmu_enable_fixed_counter_bits() only unmasks bits for counters below nr_arch_fixed_counters. [...] > + if ((data & PERF_CAP_RDPMC_METRICS_CLEAR) && > + !(data & PERF_CAP_PERF_METRICS)) > + return 1; If IA32_FIXED_CTR_CTRL.METRICS_CLEAR_EN[14] is only unmasked when the vCPU has PERF_METRICS, is this check still necessary? KVM generally doesn't police userspace's feature combinations unless it has to.