linux-kernel - Re: [PATCH v2 03/23] arm64: cpufeature: Add cpucap for PMICNTR

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Message-ID: <gsntsejq9uyb.fsf@coltonlewis-kvm.c.googlers.com>
Date: Mon, 23 Jun 2025 18:25:16 +0000
From: Colton Lewis <coltonlewis@...gle.com>
To: Oliver Upton <oliver.upton@...ux.dev>
Cc: kvm@...r.kernel.org, pbonzini@...hat.com, corbet@....net, 
	linux@...linux.org.uk, catalin.marinas@....com, will@...nel.org, 
	maz@...nel.org, joey.gouly@....com, suzuki.poulose@....com, 
	yuzenghui@...wei.com, mark.rutland@....com, shuah@...nel.org, 
	linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.linux.dev, 
	linux-perf-users@...r.kernel.org, linux-kselftest@...r.kernel.org
Subject: Re: [PATCH v2 03/23] arm64: cpufeature: Add cpucap for PMICNTR

Hi Oliver. Thanks for review.

Oliver Upton <oliver.upton@...ux.dev> writes:

> On Fri, Jun 20, 2025 at 10:13:03PM +0000, Colton Lewis wrote:
>> Add a cpucap for FEAT_PMUv3_PMICNTR, meaning there is a dedicated
>> instruction counter as well as the cycle counter.

>> Signed-off-by: Colton Lewis <coltonlewis@...gle.com>

> I don't see this capability being used in this series.

> Thanks,
> Oliver

You are correct it isn't now. I'll take it out.

>> ---
>>   arch/arm64/kernel/cpufeature.c | 7 +++++++
>>   arch/arm64/tools/cpucaps       | 1 +
>>   2 files changed, 8 insertions(+)

>> diff --git a/arch/arm64/kernel/cpufeature.c  
>> b/arch/arm64/kernel/cpufeature.c
>> index 278294fdc97d..85dea9714928 100644
>> --- a/arch/arm64/kernel/cpufeature.c
>> +++ b/arch/arm64/kernel/cpufeature.c
>> @@ -2904,6 +2904,13 @@ static const struct arm64_cpu_capabilities  
>> arm64_features[] = {
>>   		.matches = has_cpuid_feature,
>>   		ARM64_CPUID_FIELDS(ID_AA64DFR0_EL1, HPMN0, IMP)
>>   	},
>> +	{
>> +		.desc = "PMU Dedicated Instruction Counter",
>> +		.type = ARM64_CPUCAP_SYSTEM_FEATURE,
>> +		.capability = ARM64_HAS_PMICNTR,
>> +		.matches = has_cpuid_feature,
>> +		ARM64_CPUID_FIELDS(ID_AA64DFR1_EL1, PMICNTR, IMP)
>> +	},
>>   #ifdef CONFIG_ARM64_SME
>>   	{
>>   		.desc = "Scalable Matrix Extension",
>> diff --git a/arch/arm64/tools/cpucaps b/arch/arm64/tools/cpucaps
>> index 5b196ba21629..6dd72fcdd612 100644
>> --- a/arch/arm64/tools/cpucaps
>> +++ b/arch/arm64/tools/cpucaps
>> @@ -47,6 +47,7 @@ HAS_LSE_ATOMICS
>>   HAS_MOPS
>>   HAS_NESTED_VIRT
>>   HAS_PAN
>> +HAS_PMICNTR
>>   HAS_PMUV3
>>   HAS_S1PIE
>>   HAS_S1POE
>> --
>> 2.50.0.714.g196bf9f422-goog