linux-kernel - [PATCH] perf mem: Fix perf mem error on hybrid

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Date:   Tue, 28 Nov 2023 12:39:40 -0800
From:   kan.liang@...ux.intel.com
To:     acme@...nel.org, mingo@...hat.com, peterz@...radead.org,
        mark.rutland@....com, irogers@...gle.com, namhyung@...nel.org,
        jolsa@...nel.org, adrian.hunter@...el.com, ravi.bangoria@....com,
        linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org
Cc:     Kan Liang <kan.liang@...ux.intel.com>, Ammy Yi <ammy.yi@...el.com>
Subject: [PATCH] perf mem: Fix perf mem error on hybrid

From: Kan Liang <kan.liang@...ux.intel.com>

The below error can be triggered on a hybrid machine.

 $ perf mem record -t load sleep 1
 event syntax error: 'breakpoint/mem-loads,ldlat=30/P'
                                \___ Bad event or PMU

 Unable to find PMU or event on a PMU of 'breakpoint'

In the perf_mem_events__record_args(), the current perf never checks the
availability of a mem event on a given PMU. All the PMUs will be added
to the perf mem event list. Perf errors out for the unsupported PMU.

Extend perf_mem_event__supported() and take a PMU into account. Check
the mem event for each PMU before adding it to the perf mem event list.

Optimize the perf_mem_events__init() a little bit. The function is to
check whether the mem events are supported in the system. It doesn't
need to scan all PMUs. Just return with the first supported PMU is good
enough.

Fixes: 5752c20f3787 ("perf mem: Scan all PMUs instead of just core ones")
Reported-by: Ammy Yi <ammy.yi@...el.com>
Tested-by: Ammy Yi <ammy.yi@...el.com>
Signed-off-by: Kan Liang <kan.liang@...ux.intel.com>
---
 tools/perf/util/mem-events.c | 25 ++++++++++++++-----------
 1 file changed, 14 insertions(+), 11 deletions(-)

diff --git a/tools/perf/util/mem-events.c b/tools/perf/util/mem-events.c
index 954b235e12e5..3a2e3687878c 100644
--- a/tools/perf/util/mem-events.c
+++ b/tools/perf/util/mem-events.c
@@ -100,11 +100,14 @@ int perf_mem_events__parse(const char *str)
 	return -1;
 }
 
-static bool perf_mem_event__supported(const char *mnt, char *sysfs_name)
+static bool perf_mem_event__supported(const char *mnt, struct perf_pmu *pmu,
+				      struct perf_mem_event *e)
 {
+	char sysfs_name[100];
 	char path[PATH_MAX];
 	struct stat st;
 
+	scnprintf(sysfs_name, sizeof(sysfs_name), e->sysfs_name, pmu->name);
 	scnprintf(path, PATH_MAX, "%s/devices/%s", mnt, sysfs_name);
 	return !stat(path, &st);
 }
@@ -120,7 +123,6 @@ int perf_mem_events__init(void)
 
 	for (j = 0; j < PERF_MEM_EVENTS__MAX; j++) {
 		struct perf_mem_event *e = perf_mem_events__ptr(j);
-		char sysfs_name[100];
 		struct perf_pmu *pmu = NULL;
 
 		/*
@@ -136,12 +138,12 @@ int perf_mem_events__init(void)
 		 * of core PMU.
 		 */
 		while ((pmu = perf_pmus__scan(pmu)) != NULL) {
-			scnprintf(sysfs_name, sizeof(sysfs_name), e->sysfs_name, pmu->name);
-			e->supported |= perf_mem_event__supported(mnt, sysfs_name);
+			e->supported |= perf_mem_event__supported(mnt, pmu, e);
+			if (e->supported) {
+				found = true;
+				break;
+			}
 		}
-
-		if (e->supported)
-			found = true;
 	}
 
 	return found ? 0 : -ENOENT;
@@ -167,13 +169,10 @@ static void perf_mem_events__print_unsupport_hybrid(struct perf_mem_event *e,
 						    int idx)
 {
 	const char *mnt = sysfs__mount();
-	char sysfs_name[100];
 	struct perf_pmu *pmu = NULL;
 
 	while ((pmu = perf_pmus__scan(pmu)) != NULL) {
-		scnprintf(sysfs_name, sizeof(sysfs_name), e->sysfs_name,
-			  pmu->name);
-		if (!perf_mem_event__supported(mnt, sysfs_name)) {
+		if (!perf_mem_event__supported(mnt, pmu, e)) {
 			pr_err("failed: event '%s' not supported\n",
 			       perf_mem_events__name(idx, pmu->name));
 		}
@@ -183,6 +182,7 @@ static void perf_mem_events__print_unsupport_hybrid(struct perf_mem_event *e,
 int perf_mem_events__record_args(const char **rec_argv, int *argv_nr,
 				 char **rec_tmp, int *tmp_nr)
 {
+	const char *mnt = sysfs__mount();
 	int i = *argv_nr, k = 0;
 	struct perf_mem_event *e;
 
@@ -211,6 +211,9 @@ int perf_mem_events__record_args(const char **rec_argv, int *argv_nr,
 			while ((pmu = perf_pmus__scan(pmu)) != NULL) {
 				const char *s = perf_mem_events__name(j, pmu->name);
 
+				if (!perf_mem_event__supported(mnt, pmu, e))
+					continue;
+
 				rec_argv[i++] = "-e";
 				if (s) {
 					char *copy = strdup(s);
-- 
2.35.1