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

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Date:   Wed, 29 Jul 2020 10:12:50 +0100
From:   Suzuki K Poulose <suzuki.poulose@....com>
To:     liwei391@...wei.com, adrian.hunter@...el.com,
        alexander.shishkin@...ux.intel.com, acme@...nel.org,
        catalin.marinas@....com, James.Clark@....com, jolsa@...hat.com,
        leo.yan@...aro.org, mark.rutland@....com, namhyung@...nel.org,
        will@...nel.org, zhangshaokun@...ilicon.com
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        mingo@...hat.com, peterz@...radead.org, guohanjun@...wei.com
Subject: Re: [PATCH 1/4] drivers/perf: Add support for ARMv8.3-SPE

On 07/24/2020 10:16 AM, 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;
>   	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),
> +};
> +
>   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;

How do we deal with cases where we have big.LITTLE system with differing
SPE versions ?

Cheers
Suzuki