Re: [PATCH v2 0/5] Fix PMU kselftests errors on GNR/SRF/CWF

Mi, Dapeng
2025-09-11T01:59:49Z

On 9/11/2025 7:59 AM, Sean Christopherson wrote:
> On Fri, Jul 18, 2025, Dapeng Mi wrote:
>> This patch series fixes KVM PMU kselftests errors encountered on Granite
>> Rapids (GNR), Sierra Forest (SRF) and Clearwater Forest (CWF).
>>
>> GNR and SRF starts to support the timed PEBS. Timed PEBS adds a new
>> "retired latency" field in basic info group to show the timing info and
>> the PERF_CAPABILITIES[17] called "PEBS_TIMING_INFO" bit is added
>> to indicated whether timed PEBS is supported. KVM module doesn't need to
>> do any specific change to support timed PEBS except a perf change adding
>> PERF_CAP_PEBS_TIMING_INFO flag into PERF_CAP_PEBS_MASK[1]. The patch 2/5
>> adds timed PEBS support in vmx_pmu_caps_test and fix the error as the
>> PEBS caps field mismatch.
>>
>> CWF introduces 5 new architectural events (4 level-1 topdown metrics
>> events and LBR inserts event). The patch 3/5 adds support for these 5
>> arch-events and fixes the error that caused by mismatch between HW real
>> supported arch-events number with NR_INTEL_ARCH_EVENTS.
>>
>> On Intel Atom platforms, the PMU events "Instruction Retired" or
>> "Branch Instruction Retired" may be overcounted for some certain
>> instructions, like FAR CALL/JMP, RETF, IRET, VMENTRY/VMEXIT/VMPTRLD
>> and complex SGX/SMX/CSTATE instructions/flows[2].
>>
>> In details, for the Atom platforms before Sierra Forest (including
>> Sierra Forest), Both 2 events "Instruction Retired" and
>> "Branch Instruction Retired" would be overcounted on these certain
>> instructions, but for Clearwater Forest only "Instruction Retired" event
>> is overcounted on these instructions.
>>
>> As this overcount issue, pmu_counters_test and pmu_event_filter_test
>> would fail on the precise event count validation for these 2 events on
>> Atom platforms.
>>
>> To work around this Atom platform overcount issue, Patches 4-5/5 looses
>> the precise count validation separately for pmu_counters_test and
>> pmu_event_filter_test.
>>
>> BTW, this patch series doesn't depend on the mediated vPMU support.
>>
>> Changes:
>> * Add error fix for vmx_pmu_caps_test on GNR/SRF (patch 2/5).
>> * Opportunistically fix a typo (patch 1/5).
>>
>> Tests:
>> * PMU kselftests (pmu_counters_test/pmu_event_filter_test/
>> vmx_pmu_caps_test) passed on Intel SPR/GNR/SRF/CWF platforms.
>>
>> History:
>> * v1: https://lore.kernel.org/all/20250712172522.187414-1-dapeng1.mi@linux.intel.com/
>>
>> Ref:
>> [1] https://lore.kernel.org/all/20250717090302.11316-1-dapeng1.mi@linux.intel.com/
>> [2] https://edc.intel.com/content/www/us/en/design/products-and-solutions/processors-and-chipsets/sierra-forest/xeon-6700-series-processor-with-e-cores-specification-update/errata-details
>>
>> Dapeng Mi (4):
>> KVM: x86/pmu: Correct typo "_COUTNERS" to "_COUNTERS"
>> KVM: selftests: Add timing_info bit support in vmx_pmu_caps_test
>> KVM: Selftests: Validate more arch-events in pmu_counters_test
>> KVM: selftests: Relax branches event count check for event_filter test
>>
>> dongsheng (1):
>> KVM: selftests: Relax precise event count validation as overcount
>> issue
> Overall looks good, I just want to take a more infrastructure-oriented approach
> for the errata. I'll post a v3 tomorrow. All coding is done and the tests pass,
> but I want to take a second look with fresh eyes before posting it :-)

Thanks! :-)

>