linux-kernel - Re: [PATCH v3 02/10] perf: arm_spe: Support FEAT

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Message-ID: <10f63976-afa7-4e1c-bec1-d9f2447d9c13@arm.com>
Date: Thu, 12 Jun 2025 13:05:27 +0530
From: Anshuman Khandual <anshuman.khandual@....com>
To: James Clark <james.clark@...aro.org>,
 Catalin Marinas <catalin.marinas@....com>, Will Deacon <will@...nel.org>,
 Mark Rutland <mark.rutland@....com>, Jonathan Corbet <corbet@....net>,
 Marc Zyngier <maz@...nel.org>, Oliver Upton <oliver.upton@...ux.dev>,
 Joey Gouly <joey.gouly@....com>, Suzuki K Poulose <suzuki.poulose@....com>,
 Zenghui Yu <yuzenghui@...wei.com>, Peter Zijlstra <peterz@...radead.org>,
 Ingo Molnar <mingo@...hat.com>, Arnaldo Carvalho de Melo <acme@...nel.org>,
 Namhyung Kim <namhyung@...nel.org>,
 Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
 Jiri Olsa <jolsa@...nel.org>, Ian Rogers <irogers@...gle.com>,
 Adrian Hunter <adrian.hunter@...el.com>, leo.yan@....com
Cc: linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
 linux-perf-users@...r.kernel.org, linux-doc@...r.kernel.org,
 kvmarm@...ts.linux.dev
Subject: Re: [PATCH v3 02/10] perf: arm_spe: Support FEAT_SPEv1p4 filters

On 05/06/25 4:19 PM, James Clark wrote:
> FEAT_SPEv1p4 (optional from Armv8.8) adds some new filter bits, so
> remove them from the previous version's RES0 bits using
> PMSEVFR_EL1_RES0_V1P4_EXCL. It also makes some previously available bits
> unavailable again, so add those back using PMSEVFR_EL1_RES0_V1P4_INCL.

Just wondering - why cannot all the new applicable filter bits be added
explicitly for PMSEVFR_EL1_RES0_V1P4 without using exclude and include
intermediaries.

> E.g:
> 
>   E[30], bit [30]
>   When FEAT_SPEv1p4 is _not_ implemented ...
> 
> FEAT_SPE_V1P3 has the same filters as V1P2 so explicitly add it to the
> switch.
A small nit - should FEAT_SPE_V1P3 addition be done in a previous patch
as it is an already existing thing ?

> 
> Reviewed-by: Leo Yan <leo.yan@....com>
> Tested-by: Leo Yan <leo.yan@....com>
> Signed-off-by: James Clark <james.clark@...aro.org>
> ---
>  arch/arm64/include/asm/sysreg.h | 7 +++++++
>  drivers/perf/arm_spe_pmu.c      | 5 ++++-
>  2 files changed, 11 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h
> index f1bb0d10c39a..880090df3efc 100644
> --- a/arch/arm64/include/asm/sysreg.h
> +++ b/arch/arm64/include/asm/sysreg.h
> @@ -358,6 +358,13 @@
>  	(PMSEVFR_EL1_RES0_IMP & ~(BIT_ULL(18) | BIT_ULL(17) | BIT_ULL(11)))
>  #define PMSEVFR_EL1_RES0_V1P2	\
>  	(PMSEVFR_EL1_RES0_V1P1 & ~BIT_ULL(6))
> +#define PMSEVFR_EL1_RES0_V1P4_EXCL \
> +	(BIT_ULL(2) | BIT_ULL(4) | GENMASK_ULL(10, 8) | GENMASK_ULL(23, 19))
> +#define PMSEVFR_EL1_RES0_V1P4_INCL \
> +	(GENMASK_ULL(31, 26))> +#define PMSEVFR_EL1_RES0_V1P4	\
> +	(PMSEVFR_EL1_RES0_V1P4_INCL | \
> +	(PMSEVFR_EL1_RES0_V1P2 & ~PMSEVFR_EL1_RES0_V1P4_EXCL))
>  
>  /* Buffer error reporting */
>  #define PMBSR_EL1_FAULT_FSC_SHIFT	PMBSR_EL1_MSS_SHIFT
> diff --git a/drivers/perf/arm_spe_pmu.c b/drivers/perf/arm_spe_pmu.c
> index 3efed8839a4e..d9f6d229dce8 100644
> --- a/drivers/perf/arm_spe_pmu.c
> +++ b/drivers/perf/arm_spe_pmu.c
> @@ -701,9 +701,12 @@ static u64 arm_spe_pmsevfr_res0(u16 pmsver)
>  	case ID_AA64DFR0_EL1_PMSVer_V1P1:
>  		return PMSEVFR_EL1_RES0_V1P1;
>  	case ID_AA64DFR0_EL1_PMSVer_V1P2:
> +	case ID_AA64DFR0_EL1_PMSVer_V1P3:
> +		return PMSEVFR_EL1_RES0_V1P2;
> +	case ID_AA64DFR0_EL1_PMSVer_V1P4:
>  	/* Return the highest version we support in default */
>  	default:
> -		return PMSEVFR_EL1_RES0_V1P2;
> +		return PMSEVFR_EL1_RES0_V1P4;
>  	}
>  }
>  
>