linux-kernel - Re: [Patch v2 18/24] perf/x86/intel: Support arch-PEBS vector registers group capturing

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Message-ID: <a62bfd22-0469-46cc-954d-8331aa2922e9@linux.intel.com>
Date: Thu, 27 Feb 2025 14:40:00 +0800
From: "Mi, Dapeng" <dapeng1.mi@...ux.intel.com>
To: Peter Zijlstra <peterz@...radead.org>
Cc: Ingo Molnar <mingo@...hat.com>, Arnaldo Carvalho de Melo
 <acme@...nel.org>, Namhyung Kim <namhyung@...nel.org>,
 Ian Rogers <irogers@...gle.com>, Adrian Hunter <adrian.hunter@...el.com>,
 Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
 Kan Liang <kan.liang@...ux.intel.com>, Andi Kleen <ak@...ux.intel.com>,
 Eranian Stephane <eranian@...gle.com>, linux-kernel@...r.kernel.org,
 linux-perf-users@...r.kernel.org, Dapeng Mi <dapeng1.mi@...el.com>
Subject: Re: [Patch v2 18/24] perf/x86/intel: Support arch-PEBS vector
 registers group capturing


On 2/26/2025 4:08 PM, Mi, Dapeng wrote:
> On 2/25/2025 11:32 PM, Peter Zijlstra wrote:
>> On Tue, Feb 18, 2025 at 03:28:12PM +0000, Dapeng Mi wrote:
>>> Add x86/intel specific vector register (VECR) group capturing for
>>> arch-PEBS. Enable corresponding VECR group bits in
>>> GPx_CFG_C/FX0_CFG_C MSRs if users configures these vector registers
>>> bitmap in perf_event_attr and parse VECR group in arch-PEBS record.
>>>
>>> Currently vector registers capturing is only supported by PEBS based
>>> sampling, PMU driver would return error if PMI based sampling tries to
>>> capture these vector registers.
>>> @@ -676,6 +709,32 @@ int x86_pmu_hw_config(struct perf_event *event)
>>>  			return -EINVAL;
>>>  	}
>>>  
>>> +	/*
>>> +	 * Architectural PEBS supports to capture more vector registers besides
>>> +	 * XMM registers, like YMM, OPMASK and ZMM registers.
>>> +	 */
>>> +	if (unlikely(has_more_extended_regs(event))) {
>>> +		u64 caps = hybrid(event->pmu, arch_pebs_cap).caps;
>>> +
>>> +		if (!(event->pmu->capabilities & PERF_PMU_CAP_MORE_EXT_REGS))
>>> +			return -EINVAL;
>>> +
>>> +		if (has_opmask_regs(event) && !(caps & ARCH_PEBS_VECR_OPMASK))
>>> +			return -EINVAL;
>>> +
>>> +		if (has_ymmh_regs(event) && !(caps & ARCH_PEBS_VECR_YMM))
>>> +			return -EINVAL;
>>> +
>>> +		if (has_zmmh_regs(event) && !(caps & ARCH_PEBS_VECR_ZMMH))
>>> +			return -EINVAL;
>>> +
>>> +		if (has_h16zmm_regs(event) && !(caps & ARCH_PEBS_VECR_H16ZMM))
>>> +			return -EINVAL;
>>> +
>>> +		if (!event->attr.precise_ip)
>>> +			return -EINVAL;
>>> +	}
>>> +
>>>  	return x86_setup_perfctr(event);
>>>  }
>>>  
>>> diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c
>>> index f21d9f283445..8ef5b9a05fcc 100644
>>> --- a/arch/x86/events/intel/core.c
>>> +++ b/arch/x86/events/intel/core.c
>>> @@ -2963,6 +2963,18 @@ static void intel_pmu_enable_event_ext(struct perf_event *event)
>>>  			if (pebs_data_cfg & PEBS_DATACFG_XMMS)
>>>  				ext |= ARCH_PEBS_VECR_XMM & cap.caps;
>>>  
>>> +			if (pebs_data_cfg & PEBS_DATACFG_YMMS)
>>> +				ext |= ARCH_PEBS_VECR_YMM & cap.caps;
>>> +
>>> +			if (pebs_data_cfg & PEBS_DATACFG_OPMASKS)
>>> +				ext |= ARCH_PEBS_VECR_OPMASK & cap.caps;
>>> +
>>> +			if (pebs_data_cfg & PEBS_DATACFG_ZMMHS)
>>> +				ext |= ARCH_PEBS_VECR_ZMMH & cap.caps;
>>> +
>>> +			if (pebs_data_cfg & PEBS_DATACFG_H16ZMMS)
>>> +				ext |= ARCH_PEBS_VECR_H16ZMM & cap.caps;
>>> +
>>>  			if (pebs_data_cfg & PEBS_DATACFG_LBRS)
>>>  				ext |= ARCH_PEBS_LBR & cap.caps;
>>>  
>>> @@ -5115,6 +5127,9 @@ static inline void __intel_update_pmu_caps(struct pmu *pmu)
>>>  
>>>  	if (hybrid(pmu, arch_pebs_cap).caps & ARCH_PEBS_VECR_XMM)
>>>  		dest_pmu->capabilities |= PERF_PMU_CAP_EXTENDED_REGS;
>>> +
>>> +	if (hybrid(pmu, arch_pebs_cap).caps & ARCH_PEBS_VECR_EXT)
>>> +		dest_pmu->capabilities |= PERF_PMU_CAP_MORE_EXT_REGS;
>>>  }
>> There is no technical reason for it to error out, right? We can use
>> FPU/XSAVE interface to read the CPU state just fine.
> I think it's not because of technical reason. Let me confirm if we can add
> it for non-PEBS sampling.

Hi Peter,

Just double confirm, you want only PEBS sampling supports to capture SSP
and these vector registers for both *interrupt* and *user space*? or
further, you want PMI based sampling can also support to capture SSP and
these vector registers? Thanks.


>
>
>>
>>> diff --git a/arch/x86/events/intel/ds.c b/arch/x86/events/intel/ds.c
>>> index 4b01beee15f4..7e5a4202de37 100644
>>> --- a/arch/x86/events/intel/ds.c
>>> +++ b/arch/x86/events/intel/ds.c
>>> @@ -1437,9 +1438,37 @@ static u64 pebs_update_adaptive_cfg(struct perf_event *event)
>>>  	if (gprs || (attr->precise_ip < 2) || tsx_weight)
>>>  		pebs_data_cfg |= PEBS_DATACFG_GP;
>>>  
>>> -	if ((sample_type & PERF_SAMPLE_REGS_INTR) &&
>>> -	    (attr->sample_regs_intr & PERF_REG_EXTENDED_MASK))
>>> -		pebs_data_cfg |= PEBS_DATACFG_XMMS;
>>> +	if (sample_type & PERF_SAMPLE_REGS_INTR) {
>>> +		if (attr->sample_regs_intr & PERF_REG_EXTENDED_MASK)
>>> +			pebs_data_cfg |= PEBS_DATACFG_XMMS;
>>> +
>>> +		for_each_set_bit_from(bit,
>>> +			(unsigned long *)event->attr.sample_regs_intr_ext,
>>> +			PERF_NUM_EXT_REGS) {
>> This is indented wrong; please use cino=(0:0
>> if you worry about indentation depth, break out in helper function.
> Sure. would modify it.
>
>
>>> +			switch (bit + PERF_REG_EXTENDED_OFFSET) {
>>> +			case PERF_REG_X86_OPMASK0 ... PERF_REG_X86_OPMASK7:
>>> +				pebs_data_cfg |= PEBS_DATACFG_OPMASKS;
>>> +				bit = PERF_REG_X86_YMMH0 -
>>> +				      PERF_REG_EXTENDED_OFFSET - 1;
>>> +				break;
>>> +			case PERF_REG_X86_YMMH0 ... PERF_REG_X86_ZMMH0 - 1:
>>> +				pebs_data_cfg |= PEBS_DATACFG_YMMS;
>>> +				bit = PERF_REG_X86_ZMMH0 -
>>> +				      PERF_REG_EXTENDED_OFFSET - 1;
>>> +				break;
>>> +			case PERF_REG_X86_ZMMH0 ... PERF_REG_X86_ZMM16 - 1:
>>> +				pebs_data_cfg |= PEBS_DATACFG_ZMMHS;
>>> +				bit = PERF_REG_X86_ZMM16 -
>>> +				      PERF_REG_EXTENDED_OFFSET - 1;
>>> +				break;
>>> +			case PERF_REG_X86_ZMM16 ... PERF_REG_X86_ZMM_MAX - 1:
>>> +				pebs_data_cfg |= PEBS_DATACFG_H16ZMMS;
>>> +				bit = PERF_REG_X86_ZMM_MAX -
>>> +				      PERF_REG_EXTENDED_OFFSET - 1;
>>> +				break;
>>> +			}
>>> +		}
>>> +	}
>>>  
>>>  	if (sample_type & PERF_SAMPLE_BRANCH_STACK) {
>>>  		/*