linux-kernel - [PATCH 2/2] perf cs-etm: Avoid printing warning in cs_etm_is

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Date:   Wed,  8 Mar 2023 09:48:43 +0000
From:   James Clark <james.clark@....com>
To:     linux-perf-users@...r.kernel.org, acme@...nel.org
Cc:     linux-kernel@...r.kernel.org, al.grant@....com,
        James Clark <james.clark@....com>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Mike Leach <mike.leach@...aro.org>,
        Leo Yan <leo.yan@...aro.org>,
        John Garry <john.g.garry@...cle.com>,
        Will Deacon <will@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        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>, coresight@...ts.linaro.org,
        linux-arm-kernel@...ts.infradead.org
Subject: [PATCH 2/2] perf cs-etm: Avoid printing warning in cs_etm_is_ete() check

When checking for the presence of ETE, a register is read that may not
be present on older kernels or if ETE isn't available. cs_etm_get_ro()
will print a warning if it doesn't exist, so check for the existence
first before accessing it.

Signed-off-by: James Clark <james.clark@....com>
---
 tools/perf/arch/arm/util/cs-etm.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/tools/perf/arch/arm/util/cs-etm.c b/tools/perf/arch/arm/util/cs-etm.c
index 59b50dd70330..86b61ad74f90 100644
--- a/tools/perf/arch/arm/util/cs-etm.c
+++ b/tools/perf/arch/arm/util/cs-etm.c
@@ -659,8 +659,12 @@ static bool cs_etm_is_ete(struct auxtrace_record *itr, int cpu)
 {
 	struct cs_etm_recording *ptr = container_of(itr, struct cs_etm_recording, itr);
 	struct perf_pmu *cs_etm_pmu = ptr->cs_etm_pmu;
-	int trcdevarch = cs_etm_get_ro(cs_etm_pmu, cpu, metadata_ete_ro[CS_ETE_TRCDEVARCH]);
+	int trcdevarch;
 
+	if (!cs_etm_pmu_path_exists(cs_etm_pmu, cpu, metadata_ete_ro[CS_ETE_TRCDEVARCH]))
+		return false;
+
+	trcdevarch = cs_etm_get_ro(cs_etm_pmu, cpu, metadata_ete_ro[CS_ETE_TRCDEVARCH]);
 	/*
 	 * ETE if ARCHVER is 5 (ARCHVER is 4 for ETM) and ARCHPART is 0xA13.
 	 * See ETM_DEVARCH_ETE_ARCH in coresight-etm4x.h
-- 
2.34.1