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

James Clark <james.clark@xxxxxxxxxx> · Tue, 20 May 2025 14:24:23 +0100

On 20/05/2025 12:43 pm, Leo Yan wrote:
On Tue, May 06, 2025 at 12:41:39PM +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.

Signed-off-by: James Clark <james.clark@xxxxxxxxxx>
---
  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;
+
  	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);
+}

Seems to me, arm_spe_event_to_pmsdsfr() is not needed as it does not do
any conversion from event config to register value.  So simply read the
field value in opened code would be fine.

I am fine to keep it and would leave SPE driver maintainers to decide
which is preferring.  Otherwise, LGTM:

Reviewed-by: Leo Yan <leo.yan@xxxxxxx>


It's purely for consistency with the existing code. See 
arm_spe_event_to_pmsevfr() etc.

+
  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;
+
  	if (attr->exclude_idle)
  		return -EOPNOTSUPP;
  
@@ -857,6 +880,11 @@ static void arm_spe_pmu_start(struct perf_event *event, int flags)
  		write_sysreg_s(reg, SYS_PMSNEVFR_EL1);
  	}
  
+	if (spe_pmu->features & SPE_PMU_FEAT_FDS) {
+		reg = arm_spe_event_to_pmsdsfr(event);
+		write_sysreg_s(reg, SYS_PMSDSFR_EL1);
+	}
+
  	reg = arm_spe_event_to_pmslatfr(event);
  	write_sysreg_s(reg, SYS_PMSLATFR_EL1);
  
@@ -1116,6 +1144,9 @@ static void __arm_spe_pmu_dev_probe(void *info)
  	if (FIELD_GET(PMSIDR_EL1_EFT, reg))
  		spe_pmu->features |= SPE_PMU_FEAT_EFT;
  
+	if (FIELD_GET(PMSIDR_EL1_FDS, reg))
+		spe_pmu->features |= SPE_PMU_FEAT_FDS;
+
  	/* This field has a spaced out encoding, so just use a look-up */
  	fld = FIELD_GET(PMSIDR_EL1_INTERVAL, reg);
  	switch (fld) {

--
2.34.1










