From: Jim Mattson <jmattson@google.com>
To: Zide Chen <zide.chen@intel.com>
Cc: Sean Christopherson <seanjc@google.com>,
Paolo Bonzini <pbonzini@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
kvm@vger.kernel.org, Andi Kleen <ak@linux.intel.com>,
Stephane Eranian <eranian@google.com>,
linux-kernel@vger.kernel.org, Mingwei Zhang <mizhang@google.com>,
Das Sandipan <Sandipan.Das@amd.com>,
Shukla Manali <Manali.Shukla@amd.com>,
Dapeng Mi <dapeng1.mi@linux.intel.com>,
Xudong Hao <xudong.hao@intel.com>
Subject: Re: [PATCH v9 12/12] KVM: x86/pmu: Support RDPMC Metrics Clear Mode
Date: Fri, 23 Oct 2026 11:55:44 -0700 [thread overview]
Message-ID: <20261023185544.3305206-1-jmattson@google.com> (raw)
In-Reply-To: <20260918193937.569414-13-zide.chen@intel.com>
On Fri, Sep 18, 2026 at 12:39 PM Zide Chen <zide.chen@intel.com> 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.
prev parent reply other threads:[~2026-10-23 18:55 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-18 19:39 [PATCH v9 00/12] KVM: x86/pmu: Add hardware Topdown metrics support Zide Chen
2026-09-18 19:39 ` [PATCH v9 01/12] KVM: x86/pmu: Do not map fixed counters >= 3 to generic perf events Zide Chen
2026-09-18 19:39 ` [PATCH v9 02/12] KVM: x86/pmu: Support Intel fixed counter 3 on mediated vPMU Zide Chen
2026-09-18 19:39 ` [PATCH v9 03/12] KVM: x86/pmu: Rename and move vcpu_get_perf_capabilities() to pmu.h Zide Chen
2026-09-18 19:39 ` [PATCH v9 04/12] KVM: x86/pmu: Snapshot host IA32_PERF_CAPABILITIES in kvm_host Zide Chen
2026-09-18 19:39 ` [PATCH v9 05/12] KVM: x86/pmu: Support PERF_METRICS MSR in mediated vPMU Zide Chen
2026-10-23 18:27 ` Jim Mattson
2026-09-18 19:39 ` [PATCH v9 06/12] KVM: x86/pmu: Move RDPMC emulation into per-vendor callbacks Zide Chen
2026-09-18 19:39 ` [PATCH v9 07/12] KVM: x86/pmu: Emulate RDPMC on performance metrics Zide Chen
2026-10-23 18:33 ` Jim Mattson
2026-09-18 19:39 ` [PATCH v9 08/12] KVM: selftests: Add PERF_METRICS and fixed counter 3 tests Zide Chen
2026-09-18 19:39 ` [PATCH v9 09/12] perf/x86: Add INTEL_TD_METRIC_FIELD_{BITS,MASK} constants Zide Chen
2026-09-21 7:01 ` Mi, Dapeng
2026-09-18 19:39 ` [PATCH v9 10/12] perf/x86: Expose number of Topdown metric events to KVM Zide Chen
2026-09-21 7:06 ` Mi, Dapeng
2026-09-18 19:39 ` [PATCH v9 11/12] KVM: x86/pmu: Reject writes to reserved MSR_PERF_METRICS bits Zide Chen
2026-09-21 7:11 ` Mi, Dapeng
2026-10-23 18:45 ` Jim Mattson
2026-09-18 19:39 ` [PATCH v9 12/12] KVM: x86/pmu: Support RDPMC Metrics Clear Mode Zide Chen
2026-10-23 18:55 ` Jim Mattson [this message]
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