From: "Chen, Zide" <zide.chen@intel.com>
To: Andi Kleen <ak@linux.intel.com>
Cc: Sean Christopherson <seanjc@google.com>,
Paolo Bonzini <pbonzini@redhat.com>,
kvm@vger.kernel.org, Jim Mattson <jmattson@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 v8 7/8] KVM: x86/pmu: Emulate RDPMC on performance metrics
Date: Tue, 18 Aug 2026 14:59:56 -0500 [thread overview]
Message-ID: <fe9aa78c-b2b8-4660-a378-f9265afb7543@intel.com> (raw)
In-Reply-To: <aoSxVRJqjJzQssMJ@tassilo>
On 8/18/2026 2:24 PM, Andi Kleen wrote:
> On Tue, Aug 18, 2026 at 01:30:32PM -0500, Chen, Zide wrote:
>>
>>
>> On 8/18/2026 12:41 PM, Andi Kleen wrote:
>>> On Mon, Aug 17, 2026 at 11:31:41AM -0700, Zide Chen wrote:
>>>> If the host has the PERF_METRICS capability but it's not present on
>>>> the guest, RDPMC interception must be enabled and KVM should inject
>>>> an #GP when the guest attempts a PERF_METRICS RDPMC.
>>>>
>>>> If the guest has PERF_METRICS but RDPMC interception is enabled for
>>>> other reasons, KVM needs to emulate RDPMC with type 0x2000.
>>>>
>>>> For simplicity, Metrics Clear Mode is not supported.
>>>
>>> But is the bit cleared in PERF_CAPABILITIES? And would
>>> the enable bit fault?
>>
>> Currently KVM doesn't advertise
>> IA32_PERF_CAPABILITIES.RDPMC_METRICS_CLEAR[19].
>
> Thanks.
>
> How about the fault for the enable bit?
Yes, KVM always injects a #GP if the guest writes
IA32_FIXED_CTR_CTRL.METRICS_CLEAR_EN[bit 14].
>
>>> It would be better to just support it, metrics clear is actually useful.
>>
>> Sure, I'll add it.
>
> I guess it could be a follow-on patch, no need to hold up this one.
OK.
next prev parent reply other threads:[~2026-08-18 20:00 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-08-17 18:31 [PATCH v8 0/8] KVM: x86/pmu: Add hardware Topdown metrics support Zide Chen
2026-08-17 18:31 ` [PATCH v8 1/8] KVM: x86/pmu: Do not map fixed counters >= 3 to generic perf events Zide Chen
2026-08-17 18:31 ` [PATCH v8 2/8] KVM: x86/pmu: Support Intel fixed counter 3 on mediated vPMU Zide Chen
2026-08-17 18:31 ` [PATCH v8 3/8] KVM: x86/pmu: Rename and move vcpu_get_perf_capabilities() to pmu.h Zide Chen
2026-08-17 18:31 ` [PATCH v8 4/8] KVM: x86/pmu: Snapshot host IA32_PERF_CAPABILITIES in kvm_host Zide Chen
2026-08-17 18:31 ` [PATCH v8 5/8] KVM: x86/pmu: Support PERF_METRICS MSR in mediated vPMU Zide Chen
2026-08-20 0:56 ` Mi, Dapeng
2026-09-16 21:32 ` Chen, Zide
2026-08-17 18:31 ` [PATCH v8 6/8] KVM: x86/pmu: Move RDPMC emulation into per-vendor callbacks Zide Chen
2026-08-19 3:14 ` Sandipan Das
2026-08-17 18:31 ` [PATCH v8 7/8] KVM: x86/pmu: Emulate RDPMC on performance metrics Zide Chen
2026-08-18 17:41 ` Andi Kleen
2026-08-18 18:30 ` Chen, Zide
2026-08-18 19:24 ` Andi Kleen
2026-08-18 19:59 ` Chen, Zide [this message]
2026-08-17 18:31 ` [PATCH v8 8/8] KVM: selftests: Add PERF_METRICS and fixed counter 3 tests Zide Chen
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