linux-kernel - [PATCH 1/2] perf cs-etm: Handle per-thread mode on EL1 host kernel case

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Date:   Mon, 26 Jun 2023 17:10:57 +0100
From:   James Clark <james.clark@....com>
To:     linux-perf-users@...r.kernel.org
Cc:     James Clark <james.clark@....com>,
        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>,
        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>, linux-kernel@...r.kernel.org,
        coresight@...ts.linaro.org, linux-arm-kernel@...ts.infradead.org
Subject: [PATCH 1/2] perf cs-etm: Handle per-thread mode on EL1 host kernel case

In per-thread mode there are no context packets so no way to determine
which type of context packets exist. But because it's only possible to
trace host processes in per-thread mode without context packets then
assume host in this case.

This fixes the per-thread test case failures when running on nVHE:

  98: Check Arm CoreSight trace data recording and synthesized samples:
  --- start ---
  ...
  Recording trace with '-e cs_etm/timestamp=0/ --per-thread'
  Looking at perf.data file for dumping branch samples:
  CoreSight basic testing with '-e cs_etm/timestamp=0/ --per-thread': FAIL
  Recording trace with '-e cs_etm/timestamp=1/ --per-thread'
  Looking at perf.data file for dumping branch samples:
  CoreSight basic testing with '-e cs_etm/timestamp=1/ --per-thread': FAIL
  ...

Fixes: 8d3031d39fe8 ("perf cs-etm: Track exception level")
Signed-off-by: James Clark <james.clark@....com>
---
 tools/perf/util/cs-etm.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/tools/perf/util/cs-etm.c b/tools/perf/util/cs-etm.c
index 1419b40dfbe8..85821cc5650e 100644
--- a/tools/perf/util/cs-etm.c
+++ b/tools/perf/util/cs-etm.c
@@ -900,10 +900,17 @@ static struct machine *cs_etm__get_machine(struct cs_etm_queue *etmq,
 
 	/*
 	 * For any virtualisation based on nVHE (e.g. pKVM), or host kernels
-	 * running at EL1 assume everything is the host.
+	 * running at EL1, or no context IDs (per-thread mode) assume everything
+	 * is the host.
 	 */
-	if (pid_fmt == CS_ETM_PIDFMT_CTXTID)
+	switch (pid_fmt) {
+	case CS_ETM_PIDFMT_CTXTID:
+	case CS_ETM_PIDFMT_NONE:
 		return &etmq->etm->session->machines.host;
+	case CS_ETM_PIDFMT_CTXTID2:
+	default:
+		break;
+	}
 
 	/*
 	 * Not perfect, but otherwise assume anything in EL1 is the default
-- 
2.34.1