linux-kernel - Re: [PATCH v2 2/5] KVM: selftests: Add timing_info bit support in vmx_pmu_caps

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Message-ID: <3b3d361e-9543-4155-8837-037be854332f@linux.intel.com>
Date: Thu, 11 Sep 2025 09:20:15 +0800
From: "Mi, Dapeng" <dapeng1.mi@...ux.intel.com>
To: Sean Christopherson <seanjc@...gle.com>
Cc: Paolo Bonzini <pbonzini@...hat.com>, kvm@...r.kernel.org,
 linux-kernel@...r.kernel.org, Jim Mattson <jmattson@...gle.com>,
 Mingwei Zhang <mizhang@...gle.com>, Zide Chen <zide.chen@...el.com>,
 Das Sandipan <Sandipan.Das@....com>, Shukla Manali <Manali.Shukla@....com>,
 Yi Lai <yi1.lai@...el.com>, Dapeng Mi <dapeng1.mi@...el.com>
Subject: Re: [PATCH v2 2/5] KVM: selftests: Add timing_info bit support in
 vmx_pmu_caps_test


On 9/11/2025 6:03 AM, Sean Christopherson wrote:
> On Fri, Jul 18, 2025, Dapeng Mi wrote:
>> A new bit PERF_CAPABILITIES[17] called "PEBS_TIMING_INFO" bit is added
>> to indicated if PEBS supports to record timing information in a new
>> "Retried Latency" field.
>>
>> Since KVM requires user can only set host consistent PEBS capabilities,
>> otherwise the PERF_CAPABILITIES setting would fail, so add
>> pebs_timing_info bit into "immutable_caps" to block host inconsistent
>> PEBS configuration and cause errors.
> Please explain the removal of anythread_deprecated.  AFAICT, something like this
> is accurate:
>
> Opportunistically drop the anythread_deprecated bit.  It isn't and likely
> never was a PERF_CAPABILITIES flag, the test's definition snuck in when
> the union was copy+pasted from the kernel's definition.

Yes, would add this in next version. Thanks.


>
>> Signed-off-by: Dapeng Mi <dapeng1.mi@...ux.intel.com>
>> Tested-by: Yi Lai <yi1.lai@...el.com>
>> ---
>>  tools/testing/selftests/kvm/x86/vmx_pmu_caps_test.c | 3 ++-
>>  1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/tools/testing/selftests/kvm/x86/vmx_pmu_caps_test.c b/tools/testing/selftests/kvm/x86/vmx_pmu_caps_test.c
>> index a1f5ff45d518..f8deea220156 100644
>> --- a/tools/testing/selftests/kvm/x86/vmx_pmu_caps_test.c
>> +++ b/tools/testing/selftests/kvm/x86/vmx_pmu_caps_test.c
>> @@ -29,7 +29,7 @@ static union perf_capabilities {
>>  		u64 pebs_baseline:1;
>>  		u64	perf_metrics:1;
>>  		u64	pebs_output_pt_available:1;
>> -		u64	anythread_deprecated:1;
>> +		u64	pebs_timing_info:1;
>>  	};
>>  	u64	capabilities;
>>  } host_cap;
>> @@ -44,6 +44,7 @@ static const union perf_capabilities immutable_caps = {
>>  	.pebs_arch_reg = 1,
>>  	.pebs_format = -1,
>>  	.pebs_baseline = 1,
>> +	.pebs_timing_info = 1,
>>  };
>>  
>>  static const union perf_capabilities format_caps = {
>> -- 
>> 2.34.1
>>