linux-kernel - [PATCH 10/19] perf/arm-ni: Improve event validation

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Message-Id: <b1cf78c0f67dda1069f5132db9093fe0dec4c66e.1755096883.git.robin.murphy@arm.com>
Date: Wed, 13 Aug 2025 18:01:02 +0100
From: Robin Murphy <robin.murphy@....com>
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Subject: [PATCH 10/19] perf/arm-ni: Improve event validation

Although it is entirely benign for arm_ni_val_count_event() to count
any old hardware leader/sibling as an NI event (perf core will still
ultimately reject the cross-PMU group), it would still be nicer if it
didn't. Stop trying to special-case software events and simply skip any
event which doesn't belong to our PMU. Similarly drop the early return
paths since they can almost never actually return early.

Signed-off-by: Robin Murphy <robin.murphy@....com>
---
 drivers/perf/arm-ni.c | 29 +++++++++++++----------------
 1 file changed, 13 insertions(+), 16 deletions(-)

diff --git a/drivers/perf/arm-ni.c b/drivers/perf/arm-ni.c
index 1615a0564031..d6b683a0264e 100644
--- a/drivers/perf/arm-ni.c
+++ b/drivers/perf/arm-ni.c
@@ -271,40 +271,37 @@ static void arm_ni_pmu_disable(struct pmu *pmu)
 }
 
 struct arm_ni_val {
+	const struct pmu *pmu;
 	unsigned int evcnt;
 	unsigned int ccnt;
 };
 
-static bool arm_ni_val_count_event(struct perf_event *evt, struct arm_ni_val *val)
+static void arm_ni_val_count_event(struct perf_event *evt, struct arm_ni_val *val)
 {
-	if (is_software_event(evt))
-		return true;
-
-	if (NI_EVENT_TYPE(evt) == NI_PMU) {
-		val->ccnt++;
-		return val->ccnt <= 1;
+	if (evt->pmu == val->pmu) {
+		if (NI_EVENT_TYPE(evt) == NI_PMU)
+			val->ccnt++;
+		else
+			val->evcnt++;
 	}
-
-	val->evcnt++;
-	return val->evcnt <= NI_NUM_COUNTERS;
 }
 
 static int arm_ni_validate_group(struct perf_event *event)
 {
 	struct perf_event *sibling, *leader = event->group_leader;
-	struct arm_ni_val val = { 0 };
+	struct arm_ni_val val = { .pmu = event->pmu };
 
 	if (leader == event)
 		return 0;
 
 	arm_ni_val_count_event(event, &val);
-	if (!arm_ni_val_count_event(leader, &val))
+	arm_ni_val_count_event(leader, &val);
+	for_each_sibling_event(sibling, leader)
+		arm_ni_val_count_event(sibling, &val);
+
+	if (val.evcnt > NI_NUM_COUNTERS || val.ccnt > 1)
 		return -EINVAL;
 
-	for_each_sibling_event(sibling, leader) {
-		if (!arm_ni_val_count_event(sibling, &val))
-			return -EINVAL;
-	}
 	return 0;
 }
 
-- 
2.39.2.101.g768bb238c484.dirty