linux-kernel - Re: [PATCH 1/4] drivers/perf: Add support for ARMv8.3-SPE

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Message-ID: <c2ce17a9-bd3a-e828-fe76-769c9feabece@huawei.com>
Date:   Tue, 28 Jul 2020 21:24:42 +0800
From:   "liwei (GF)" <liwei391@...wei.com>
To:     Leo Yan <leo.yan@...aro.org>, Will Deacon <will@...nel.org>
CC:     Adrian Hunter <adrian.hunter@...el.com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        James Clark <james.clark@....com>,
        Jiri Olsa <jolsa@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        Namhyung Kim <namhyung@...nel.org>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        <zhangshaokun@...ilicon.com>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, "Ingo Molnar" <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>, <guohanjun@...wei.com>
Subject: Re: [PATCH 1/4] drivers/perf: Add support for ARMv8.3-SPE

Hi Leo,

On 2020/7/28 20:27, Leo Yan wrote:
> Hi Wei,
> 
> On Fri, Jul 24, 2020 at 05:16:04PM +0800, Wei Li wrote:
>> Armv8.3 extends the SPE by adding:
>> - Alignment field in the Events packet, and filtering on this event
>>   using PMSEVFR_EL1.
>> - Support for the Scalable Vector Extension (SVE).
>>
>> The main additions for SVE are:
>> - Recording the vector length for SVE operations in the Operation Type
>>   packet. It is not possible to filter on vector length.
>> - Incomplete predicate and empty predicate fields in the Events packet,
>>   and filtering on these events using PMSEVFR_EL1.
>>
>> Update the check of pmsevfr for empty/partial predicated SVE and
>> alignment event in kernel driver.
>>
>> Signed-off-by: Wei Li <liwei391@...wei.com>
>> ---
>>  arch/arm64/include/asm/sysreg.h |  4 +++-
>>  drivers/perf/arm_spe_pmu.c      | 18 ++++++++++++++----
>>  2 files changed, 17 insertions(+), 5 deletions(-)
>>
>> diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h
>> index 463175f80341..be4c44ccdb56 100644
>> --- a/arch/arm64/include/asm/sysreg.h
>> +++ b/arch/arm64/include/asm/sysreg.h
>> @@ -281,7 +281,6 @@
>>  #define SYS_PMSFCR_EL1_ST_SHIFT		18
>>  
>>  #define SYS_PMSEVFR_EL1			sys_reg(3, 0, 9, 9, 5)
>> -#define SYS_PMSEVFR_EL1_RES0		0x0000ffff00ff0f55UL
>>  
>>  #define SYS_PMSLATFR_EL1		sys_reg(3, 0, 9, 9, 6)
>>  #define SYS_PMSLATFR_EL1_MINLAT_SHIFT	0
>> @@ -769,6 +768,9 @@
>>  #define ID_AA64DFR0_PMUVER_8_5		0x6
>>  #define ID_AA64DFR0_PMUVER_IMP_DEF	0xf
>>  
>> +#define ID_AA64DFR0_PMSVER_8_2		0x1
>> +#define ID_AA64DFR0_PMSVER_8_3		0x2
>> +
>>  #define ID_DFR0_PERFMON_SHIFT		24
>>  
>>  #define ID_DFR0_PERFMON_8_1		0x4
>> diff --git a/drivers/perf/arm_spe_pmu.c b/drivers/perf/arm_spe_pmu.c
>> index e51ddb6d63ed..5ec7ee0c8fa1 100644
>> --- a/drivers/perf/arm_spe_pmu.c
>> +++ b/drivers/perf/arm_spe_pmu.c
>> @@ -54,7 +54,7 @@ struct arm_spe_pmu {
>>  	struct hlist_node			hotplug_node;
>>  
>>  	int					irq; /* PPI */
>> -
>> +	int					pmuver;
> 
> Since the version number is only 4 bits width, 'u16' would be enough
> to record SPE version number.

Sounds reasonable, i can change it to 'u16' if you insist.

>>  	u16					min_period;
>>  	u16					counter_sz;
>>  
>> @@ -80,6 +80,15 @@ struct arm_spe_pmu {
>>  /* Keep track of our dynamic hotplug state */
>>  static enum cpuhp_state arm_spe_pmu_online;
>>  
>> +static u64 sys_pmsevfr_el1_mask[] = {
>> +	[ID_AA64DFR0_PMSVER_8_2] = GENMASK_ULL(63, 48) | GENMASK_ULL(31, 24) |
>> +		GENMASK_ULL(15, 12) | BIT_ULL(7) | BIT_ULL(5) | BIT_ULL(3) |
>> +		BIT_ULL(1),
>> +	[ID_AA64DFR0_PMSVER_8_3] = GENMASK_ULL(63, 48) | GENMASK_ULL(31, 24) |
>> +		GENMASK_ULL(18, 17) | GENMASK_ULL(15, 11) | BIT_ULL(7) |
>> +		BIT_ULL(5) | BIT_ULL(3) | BIT_ULL(1),
>> +};
> 
> Seems to me, the definitions for Aarch64 system registers should be
> placed into the file 'arch/arm64/include/asm/sysreg.h'.  Like below
> two macros:
> 
>   #define SYS_PMSEVFR_EL1_RES0_8_2		0x0000ffff00ff0f55UL
>   #define SYS_PMSEVFR_EL1_RES0_8_3		...

I really think using GENMASK_ULL() to generate the mask is better than a definition
with magic number. It is beneficial to be reviewed and extended later.

> Let's wait for Will or Mark Rutland's comments for this, in case I
> mislead for this.
>> +
>>  enum arm_spe_pmu_buf_fault_action {
>>  	SPE_PMU_BUF_FAULT_ACT_SPURIOUS,
>>  	SPE_PMU_BUF_FAULT_ACT_FATAL,
>> @@ -670,7 +679,7 @@ static int arm_spe_pmu_event_init(struct perf_event *event)
>>  	    !cpumask_test_cpu(event->cpu, &spe_pmu->supported_cpus))
>>  		return -ENOENT;
>>  
>> -	if (arm_spe_event_to_pmsevfr(event) & SYS_PMSEVFR_EL1_RES0)
>> +	if (arm_spe_event_to_pmsevfr(event) & ~sys_pmsevfr_el1_mask[spe_pmu->pmuver])
>>  		return -EOPNOTSUPP;
>>  
>>  	if (attr->exclude_idle)
>> @@ -937,6 +946,7 @@ static void __arm_spe_pmu_dev_probe(void *info)
>>  			fld, smp_processor_id());
>>  		return;
>>  	}
>> +	spe_pmu->pmuver = fld;
>>  
>>  	/* Read PMBIDR first to determine whether or not we have access */
>>  	reg = read_sysreg_s(SYS_PMBIDR_EL1);
>> @@ -1027,8 +1037,8 @@ static void __arm_spe_pmu_dev_probe(void *info)
>>  	}
>>  
>>  	dev_info(dev,
>> -		 "probed for CPUs %*pbl [max_record_sz %u, align %u, features 0x%llx]\n",
>> -		 cpumask_pr_args(&spe_pmu->supported_cpus),
>> +		 "v%d probed for CPUs %*pbl [max_record_sz %u, align %u, features 0x%llx]\n",
> 
> Let's output explict info, like:
> 
>   "probed for CPUs %*pbl [pmuver %d, max_record_sz %u, align %u, features 0x%llx]\n",
> 

Agree, and i have a little question here:
Currently, the of_compatible of SPE PMU is "arm,statistical-profiling-extension-v1", and
the platform_device name is "arm,spe-v1". So this message looks weird when supporting
ARMv8.3-SPE because the pmuver is 2.

As the version of SPE can be probed by reading 'ID_AA64DFR0_EL1.PMSVer', can we remove
the version hint in of_compatible and platform_device name?

> 
>> +		 spe_pmu->pmuver, cpumask_pr_args(&spe_pmu->supported_cpus),
>>  		 spe_pmu->max_record_sz, spe_pmu->align, spe_pmu->features);
>>  
>>  	spe_pmu->features |= SPE_PMU_FEAT_DEV_PROBED;
>> -- 
>> 2.17.1
>>

Thanks,
Wei