Re: [PATCH v3 07/10] perf: arm_spe: Add support for filtering on data source

Will Deacon
2025-07-14T14:19:13Z

On Thu, Jun 05, 2025 at 11:49:05AM +0100, James Clark wrote:
> SPE_FEAT_FDS adds the ability to filter on the data source of packets.
> Like the other existing filters, enable filtering with PMSFCR_EL1.FDS
> when any of the filter bits are set.
>
> Each bit maps to data sources 0-63 described by bits[0:5] in the data
> source packet (although the full range of data source is 16 bits so
> higher value data sources can't be filtered on). The filter is an OR of
> all the bits, so for example setting bits 0 and 3 filters packets from
> data sources 0 OR 3.
>
> 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>
> ---
> drivers/perf/arm_spe_pmu.c | 31 +++++++++++++++++++++++++++++++
> 1 file changed, 31 insertions(+)
>
> diff --git a/drivers/perf/arm_spe_pmu.c b/drivers/perf/arm_spe_pmu.c
> index 9309b846f642..d04318411f77 100644
> --- a/drivers/perf/arm_spe_pmu.c
> +++ b/drivers/perf/arm_spe_pmu.c
> @@ -87,6 +87,7 @@ struct arm_spe_pmu {
> #define SPE_PMU_FEAT_INV_FILT_EVT (1UL << 6)
> #define SPE_PMU_FEAT_DISCARD (1UL << 7)
> #define SPE_PMU_FEAT_EFT (1UL << 8)
> +#define SPE_PMU_FEAT_FDS (1UL << 9)
> #define SPE_PMU_FEAT_DEV_PROBED (1UL << 63)
> u64 features;
>
> @@ -232,6 +233,10 @@ static const struct attribute_group arm_spe_pmu_cap_group = {
> #define ATTR_CFG_FLD_inv_event_filter_LO 0
> #define ATTR_CFG_FLD_inv_event_filter_HI 63
>
> +#define ATTR_CFG_FLD_data_src_filter_CFG config4 /* PMSDSFR_EL1 */
> +#define ATTR_CFG_FLD_data_src_filter_LO 0
> +#define ATTR_CFG_FLD_data_src_filter_HI 63
> +
> GEN_PMU_FORMAT_ATTR(ts_enable);
> GEN_PMU_FORMAT_ATTR(pa_enable);
> GEN_PMU_FORMAT_ATTR(pct_enable);
> @@ -248,6 +253,7 @@ GEN_PMU_FORMAT_ATTR(float_filter);
> GEN_PMU_FORMAT_ATTR(float_filter_mask);
> GEN_PMU_FORMAT_ATTR(event_filter);
> GEN_PMU_FORMAT_ATTR(inv_event_filter);
> +GEN_PMU_FORMAT_ATTR(data_src_filter);
> GEN_PMU_FORMAT_ATTR(min_latency);
> GEN_PMU_FORMAT_ATTR(discard);
>
> @@ -268,6 +274,7 @@ static struct attribute *arm_spe_pmu_formats_attr[] = {
> &format_attr_float_filter_mask.attr,
> &format_attr_event_filter.attr,
> &format_attr_inv_event_filter.attr,
> + &format_attr_data_src_filter.attr,
> &format_attr_min_latency.attr,
> &format_attr_discard.attr,
> NULL,
> @@ -286,6 +293,9 @@ static umode_t arm_spe_pmu_format_attr_is_visible(struct kobject *kobj,
> if (attr == &format_attr_inv_event_filter.attr && !(spe_pmu->features & SPE_PMU_FEAT_INV_FILT_EVT))
> return 0;
>
> + if (attr == &format_attr_data_src_filter.attr && !(spe_pmu->features & SPE_PMU_FEAT_FDS))
> + return 0;
> +
> if ((attr == &format_attr_branch_filter_mask.attr ||
> attr == &format_attr_load_filter_mask.attr ||
> attr == &format_attr_store_filter_mask.attr ||
> @@ -406,6 +416,9 @@ static u64 arm_spe_event_to_pmsfcr(struct perf_event *event)
> if (ATTR_CFG_GET_FLD(attr, inv_event_filter))
> reg |= PMSFCR_EL1_FnE;
>
> + if (ATTR_CFG_GET_FLD(attr, data_src_filter))
> + reg |= PMSFCR_EL1_FDS;

Is the polarity correct here? The description of PMSDSFR_EL1.S<m> suggests
that setting bits to 1 _excludes_ the FDS filtering.

> if (ATTR_CFG_GET_FLD(attr, min_latency))
> reg |= PMSFCR_EL1_FL;
>
> @@ -430,6 +443,12 @@ static u64 arm_spe_event_to_pmslatfr(struct perf_event *event)
> return FIELD_PREP(PMSLATFR_EL1_MINLAT, ATTR_CFG_GET_FLD(attr, min_latency));
> }
>
> +static u64 arm_spe_event_to_pmsdsfr(struct perf_event *event)
> +{
> + struct perf_event_attr *attr = &event->attr;
> + return ATTR_CFG_GET_FLD(attr, data_src_filter);
> +}
> +
> static void arm_spe_pmu_pad_buf(struct perf_output_handle *handle, int len)
> {
> struct arm_spe_pmu_buf *buf = perf_get_aux(handle);
> @@ -788,6 +807,10 @@ static int arm_spe_pmu_event_init(struct perf_event *event)
> if (arm_spe_event_to_pmsnevfr(event) & arm_spe_pmsevfr_res0(spe_pmu->pmsver))
> return -EOPNOTSUPP;
>
> + if (arm_spe_event_to_pmsdsfr(event) &&
> + !(spe_pmu->features & SPE_PMU_FEAT_FDS))
> + return -EOPNOTSUPP;

Same question here.

Will