linux-kernel - [PATCH] perf arm-spe: Report error if set frequency

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Message-Id: <20250205183009.224182-1-leo.yan@arm.com>
Date: Wed,  5 Feb 2025 18:30:09 +0000
From: Leo Yan <leo.yan@....com>
To: Arnaldo Carvalho de Melo <acme@...nel.org>,
	James Clark <james.clark@...aro.org>,
	Namhyung Kim <namhyung@...nel.org>,
	Mark Rutland <mark.rutland@....com>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	Jiri Olsa <jolsa@...nel.org>,
	Ian Rogers <irogers@...gle.com>,
	Adrian Hunter <adrian.hunter@...el.com>,
	"Liang, Kan" <kan.liang@...ux.intel.com>,
	linux-arm-kernel@...ts.infradead.org,
	linux-perf-users@...r.kernel.org,
	linux-kernel@...r.kernel.org
Cc: Leo Yan <leo.yan@....com>
Subject: [PATCH] perf arm-spe: Report error if set frequency

When users set the parameter '-F' to specify frequency for Arm SPE, the
tool reports error:

  perf record -F 1000 -e arm_spe_0// -- sleep 1
  Error:
  Invalid event (arm_spe_0//) in per-thread mode, enable system wide with '-a'.

The output logs are confused and it does not give the correct reminding.
Arm SPE does not support frequency setting given it adopts a statistical
based approach.

Alternatively, Arm SPE supports setting period.  This commit adds a
for frequency setting.  It reports error and reminds users to set period
instead.

After:

  perf record -F 100 -e arm_spe_0// -- sleep 1
  Arm SPE: Frequency is not supported. Check manual 'man perf-record' on how to set period.

Signed-off-by: Leo Yan <leo.yan@....com>
---
 tools/perf/arch/arm64/util/arm-spe.c | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/tools/perf/arch/arm64/util/arm-spe.c b/tools/perf/arch/arm64/util/arm-spe.c
index 4301181b8e45..baef0812dc19 100644
--- a/tools/perf/arch/arm64/util/arm-spe.c
+++ b/tools/perf/arch/arm64/util/arm-spe.c
@@ -40,6 +40,19 @@ struct arm_spe_recording {
 	bool			*wrapped;
 };
 
+/* Iterate config list to detect if the "freq" parameter is set */
+static bool arm_spe_is_set_freq(struct evsel *evsel)
+{
+	struct evsel_config_term *term;
+
+	list_for_each_entry(term, &evsel->config_terms, list) {
+		if (term->type == EVSEL__CONFIG_TERM_FREQ)
+			return true;
+	}
+
+	return false;
+}
+
 /*
  * arm_spe_find_cpus() returns a new cpu map, and the caller should invoke
  * perf_cpu_map__put() to release the map after use.
@@ -389,6 +402,13 @@ static int arm_spe_recording_options(struct auxtrace_record *itr,
 				return -EINVAL;
 			}
 			opts->full_auxtrace = true;
+
+			if (opts->user_freq != UINT_MAX ||
+			    arm_spe_is_set_freq(evsel)) {
+				pr_err("Arm SPE: Frequency is not supported. "
+				       "Check manual 'man perf-record' on how to set period.\n");
+				return -EINVAL;
+			}
 		}
 	}
 
-- 
2.34.1