Patch "perf cs-etm: Fix timeless decode mode detection" has been added to the 6.2-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    perf cs-etm: Fix timeless decode mode detection

to the 6.2-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     perf-cs-etm-fix-timeless-decode-mode-detection.patch
and it can be found in the queue-6.2 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit dd3c69a5950d2928913c57d1774fed7d7774851f
Author: James Clark <james.clark@xxxxxxx>
Date:   Mon Apr 24 14:47:41 2023 +0100

    perf cs-etm: Fix timeless decode mode detection
    
    [ Upstream commit 449067f3fc9f340da54e383738286881e6634d0b ]
    
    In this context, timeless refers to the trace data rather than the perf
    event data. But when detecting whether there are timestamps in the trace
    data or not, the presence of a timestamp flag on any perf event is used.
    
    Since commit f42c0ce573df ("perf record: Always get text_poke events
    with --kcore option") timestamps were added to a tracking event when
    --kcore is used which breaks this detection mechanism. Fix it by
    detecting if trace timestamps exist by looking at the ETM config flags.
    This would have always been a more accurate way of doing it anyway.
    
    This fixes the following error message when using --kcore with
    Coresight:
    
      $ perf record --kcore -e cs_etm// --per-thread
      $ perf report
      The perf.data/data data has no samples!
    
    Fixes: f42c0ce573df79d1 ("perf record: Always get text_poke events with --kcore option")
    Reported-by: Yang Shi <shy828301@xxxxxxxxx>
    Signed-off-by: James Clark <james.clark@xxxxxxx>
    Cc: Adrian Hunter <adrian.hunter@xxxxxxxxx>
    Cc: Alexander Shishkin <alexander.shishkin@xxxxxxxxxxxxxxx>
    Cc: Ian Rogers <irogers@xxxxxxxxxx>
    Cc: Ingo Molnar <mingo@xxxxxxxxxx>
    Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
    Cc: John Garry <john.g.garry@xxxxxxxxxx>
    Cc: Leo Yan <leo.yan@xxxxxxxxxx>
    Cc: Mark Rutland <mark.rutland@xxxxxxx>
    Cc: Mathieu Poirier <mathieu.poirier@xxxxxxxxxx>
    Cc: Mike Leach <mike.leach@xxxxxxxxxx>
    Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
    Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
    Cc: Suzuki Poulouse <suzuki.poulose@xxxxxxx>
    Cc: Will Deacon <will@xxxxxxxxxx>
    Cc: coresight@xxxxxxxxxxxxxxxx
    Cc: denik@xxxxxxxxxx
    Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
    Link: https://lore.kernel.org/lkml/CAHbLzkrJQTrYBtPkf=jf3OpQ-yBcJe7XkvQstX9j2frz4WF-SQ@xxxxxxxxxxxxxx/
    Link: https://lore.kernel.org/r/20230424134748.228137-2-james.clark@xxxxxxx
    Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/tools/perf/util/cs-etm.c b/tools/perf/util/cs-etm.c
index 33303d03c2fa4..2f327986090e1 100644
--- a/tools/perf/util/cs-etm.c
+++ b/tools/perf/util/cs-etm.c
@@ -2488,26 +2488,29 @@ static int cs_etm__process_auxtrace_event(struct perf_session *session,
 	return 0;
 }
 
-static bool cs_etm__is_timeless_decoding(struct cs_etm_auxtrace *etm)
+static int cs_etm__setup_timeless_decoding(struct cs_etm_auxtrace *etm)
 {
 	struct evsel *evsel;
 	struct evlist *evlist = etm->session->evlist;
-	bool timeless_decoding = true;
 
 	/* Override timeless mode with user input from --itrace=Z */
-	if (etm->synth_opts.timeless_decoding)
-		return true;
+	if (etm->synth_opts.timeless_decoding) {
+		etm->timeless_decoding = true;
+		return 0;
+	}
 
 	/*
-	 * Circle through the list of event and complain if we find one
-	 * with the time bit set.
+	 * Find the cs_etm evsel and look at what its timestamp setting was
 	 */
-	evlist__for_each_entry(evlist, evsel) {
-		if ((evsel->core.attr.sample_type & PERF_SAMPLE_TIME))
-			timeless_decoding = false;
-	}
+	evlist__for_each_entry(evlist, evsel)
+		if (cs_etm__evsel_is_auxtrace(etm->session, evsel)) {
+			etm->timeless_decoding =
+				!(evsel->core.attr.config & BIT(ETM_OPT_TS));
+			return 0;
+		}
 
-	return timeless_decoding;
+	pr_err("CS ETM: Couldn't find ETM evsel\n");
+	return -EINVAL;
 }
 
 /*
@@ -2884,7 +2887,6 @@ int cs_etm__process_auxtrace_info_full(union perf_event *event,
 	etm->snapshot_mode = (ptr[CS_ETM_SNAPSHOT] != 0);
 	etm->metadata = metadata;
 	etm->auxtrace_type = auxtrace_info->type;
-	etm->timeless_decoding = cs_etm__is_timeless_decoding(etm);
 
 	etm->auxtrace.process_event = cs_etm__process_event;
 	etm->auxtrace.process_auxtrace_event = cs_etm__process_auxtrace_event;
@@ -2894,6 +2896,10 @@ int cs_etm__process_auxtrace_info_full(union perf_event *event,
 	etm->auxtrace.evsel_is_auxtrace = cs_etm__evsel_is_auxtrace;
 	session->auxtrace = &etm->auxtrace;
 
+	err = cs_etm__setup_timeless_decoding(etm);
+	if (err)
+		return err;
+
 	etm->unknown_thread = thread__new(999999999, 999999999);
 	if (!etm->unknown_thread) {
 		err = -ENOMEM;