linux-kernel - [PATCH v1 2/2] perf list pfm: Retry supported test with exclude

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Date:   Wed,  6 Sep 2023 16:44:16 -0700
From:   Ian Rogers <irogers@...gle.com>
To:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Ian Rogers <irogers@...gle.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Thomas Richter <tmricht@...ux.ibm.com>,
        Kan Liang <kan.liang@...ux.intel.com>,
        Zhengjun Xing <zhengjun.xing@...ux.intel.com>,
        Kang Minchul <tegongkang@...il.com>,
        linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH v1 2/2] perf list pfm: Retry supported test with exclude_kernel

With paranoia set at 2 evsel__open will fail with EACCES for non-root
users. To avoid this stopping libpfm4 events from being printed, retry
with exclude_kernel enabled - copying the regular is_event_supported
test.

Signed-off-by: Ian Rogers <irogers@...gle.com>
---
 tools/perf/util/pfm.c | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/tools/perf/util/pfm.c b/tools/perf/util/pfm.c
index 862e4a689868..5ccfe4b64cdf 100644
--- a/tools/perf/util/pfm.c
+++ b/tools/perf/util/pfm.c
@@ -145,7 +145,20 @@ static bool is_libpfm_event_supported(const char *name, struct perf_cpu_map *cpu
 
 	evsel->is_libpfm_event = true;
 
-	if (evsel__open(evsel, cpus, threads) < 0)
+	ret = evsel__open(evsel, cpus, threads);
+	if (ret == -EACCES) {
+		/*
+		 * This happens if the paranoid value
+		 * /proc/sys/kernel/perf_event_paranoid is set to 2
+		 * Re-run with exclude_kernel set; we don't do that
+		 * by default as some ARM machines do not support it.
+		 *
+		 */
+		evsel->core.attr.exclude_kernel = 1;
+		ret = evsel__open(evsel, cpus, threads);
+
+	}
+	if (ret < 0)
 		result = false;
 
 	evsel__close(evsel);
-- 
2.42.0.283.g2d96d420d3-goog