Re: [PATCH v3 02/10] perf: arm_spe: Support FEAT_SPEv1p4 filters

James Clark
2025-06-12T09:56:13Z

On 12/06/2025 8:35 am, Anshuman Khandual wrote:
> 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.
>

They could but there would be a lot of duplication. Each version tended
to add only a few bits to the previous version. Also for consistency,
they were already defined in this way. I didn't think there was much to
gain by redefining the whole bitset just for this one, it's probably
going to look just as messy.

>> 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 ?
>

It's related to this patch because I change the default case. Before
V1P3 hits 'default:' and returns PMSEVFR_EL1_RES0_V1P2. But now the
highest supported is PMSEVFR_EL1_RES0_V1P4 for the default case so I
need to add a case for V1P3 to keep it returning PMSEVFR_EL1_RES0_V1P2
filters. There's no bug.

>>
>> Reviewed-by: Leo Yan <leo.yan@arm.com>
>> Tested-by: Leo Yan <leo.yan@arm.com>
>> Signed-off-by: James Clark <james.clark@linaro.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;
>> }
>> }
>>
>>
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