linux-kernel - [PATCH v1 1/2] perf cs-etm: Validate timestamp tracing in per-thread mode

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Message-Id: <20230827133557.112494-2-leo.yan@linaro.org>
Date:   Sun, 27 Aug 2023 21:35:56 +0800
From:   Leo Yan <leo.yan@...aro.org>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        James Clark <james.clark@....com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Mike Leach <mike.leach@...aro.org>,
        John Garry <john.g.garry@...cle.com>,
        Will Deacon <will@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.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>,
        coresight@...ts.linaro.org, linux-arm-kernel@...ts.infradead.org,
        linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     Leo Yan <leo.yan@...aro.org>
Subject: [PATCH v1 1/2] perf cs-etm: Validate timestamp tracing in per-thread mode

So far, it's impossible to validate timestamp trace in Arm CoreSight when
the perf is in the per-thread mode.  E.g. for the command:

  perf record -e cs_etm/timestamp/ --per-thread -- ls

The command enables config 'timestamp' for 'cs_etm' event in the
per-thread mode.  In this case, the function cs_etm_validate_config()
directly bails out and skips validation.

Given profiled process can be scheduled on any CPUs in the per-thread
mode, this patch validates timestamp tracing for all CPUs when detect
the CPU map is empty.

Signed-off-by: Leo Yan <leo.yan@...aro.org>
---
 tools/perf/arch/arm/util/cs-etm.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/tools/perf/arch/arm/util/cs-etm.c b/tools/perf/arch/arm/util/cs-etm.c
index b8d6a953fd74..cf9ef9ba800b 100644
--- a/tools/perf/arch/arm/util/cs-etm.c
+++ b/tools/perf/arch/arm/util/cs-etm.c
@@ -205,8 +205,17 @@ static int cs_etm_validate_config(struct auxtrace_record *itr,
 	for (i = 0; i < cpu__max_cpu().cpu; i++) {
 		struct perf_cpu cpu = { .cpu = i, };
 
-		if (!perf_cpu_map__has(event_cpus, cpu) ||
-		    !perf_cpu_map__has(online_cpus, cpu))
+		/*
+		 * In per-cpu case, do the validation for CPUs to work with.
+		 * In per-thread case, the CPU map is empty.  Since the traced
+		 * program can run on any CPUs in this case, thus don't skip
+		 * validation.
+		 */
+		if (!perf_cpu_map__empty(event_cpus) &&
+		    !perf_cpu_map__has(event_cpus, cpu))
+			continue;
+
+		if (!perf_cpu_map__has(online_cpus, cpu))
 			continue;
 
 		err = cs_etm_validate_context_id(itr, evsel, i);
-- 
2.34.1