linux-kernel - [PATCH v2 2/2] perf cs-etm: Test sparse CPU maps

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Message-Id: <20260119-james-perf-coresight-cpu-map-segfault-v2-2-56b956a629ee@linaro.org>
Date: Mon, 19 Jan 2026 10:18:36 +0000
From: James Clark <james.clark@...aro.org>
To: Suzuki K Poulose <suzuki.poulose@....com>, 
 Mike Leach <mike.leach@...aro.org>, John Garry <john.g.garry@...cle.com>, 
 Will Deacon <will@...nel.org>, Leo Yan <leo.yan@...ux.dev>, 
 Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>, 
 Arnaldo Carvalho de Melo <acme@...nel.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>, 
 Thomas Falcon <thomas.falcon@...el.com>
Cc: coresight@...ts.linaro.org, linux-arm-kernel@...ts.infradead.org, 
 linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org, 
 James Clark <james.clark@...aro.org>
Subject: [PATCH v2 2/2] perf cs-etm: Test sparse CPU maps

We only currently test with default (all CPUs) or --per-thread mode.
Different permutations of the "-C" option can affect decoding so add
tests for some of them.

Signed-off-by: James Clark <james.clark@...aro.org>
---
 tools/perf/tests/shell/test_arm_coresight.sh | 54 ++++++++++++++++++++++++++++
 1 file changed, 54 insertions(+)

diff --git a/tools/perf/tests/shell/test_arm_coresight.sh b/tools/perf/tests/shell/test_arm_coresight.sh
index 1c750b67d141..bbf89e944e7b 100755
--- a/tools/perf/tests/shell/test_arm_coresight.sh
+++ b/tools/perf/tests/shell/test_arm_coresight.sh
@@ -198,6 +198,58 @@ arm_cs_etm_basic_test() {
 	arm_cs_report "CoreSight basic testing with '$*'" $err
 }
 
+arm_cs_etm_test_cpu_list() {
+	echo "Testing sparse CPU list: $1"
+	perf record -o ${perfdata} -e cs_etm//u -C $1 \
+		-- taskset --cpu-list $1 true > /dev/null 2>&1
+	perf_script_branch_samples true
+	err=$?
+	arm_cs_report "CoreSight sparse CPUs with '$*'" $err
+}
+
+arm_cs_etm_sparse_cpus_test() {
+	# Iterate for every ETM device
+	cpus=()
+	for dev in /sys/bus/event_source/devices/cs_etm/cpu*; do
+		# Canonicalize the path
+		dev=`readlink -f $dev`
+
+		# Find the ETM device belonging to which CPU
+		cpus+=("$(cat $dev/cpu)")
+	done
+
+	mapfile -t cpus < <(printf '%s\n' "${cpus[@]}" | sort -n)
+	total=${#cpus[@]}
+
+	# Need more than 1 to test
+	if [ $total -le 1 ]; then
+		return 0
+	fi
+
+	half=$((total / 2))
+
+	# First half
+	first_half=$(IFS=,; echo "${cpus[*]:0:$half}")
+	arm_cs_etm_test_cpu_list $first_half
+
+	# Second half
+	second_half=$(IFS=,; echo "${cpus[*]:$half}")
+	arm_cs_etm_test_cpu_list $second_half
+
+	# Odd list is the same as halves unless >= 4 CPUs
+	if [ $total -lt 4 ]; then
+		return 0
+	fi
+
+	# Odd indices
+	odd_cpus=()
+	for ((i=1; i<total; i+=2)); do
+		odd_cpus+=("${cpus[$i]}")
+	done
+	odd_list=$(IFS=,; echo "${odd_cpus[*]}")
+	arm_cs_etm_test_cpu_list $odd_list
+}
+
 arm_cs_etm_traverse_path_test
 arm_cs_etm_system_wide_test
 arm_cs_etm_snapshot_test
@@ -211,4 +263,6 @@ arm_cs_etm_basic_test -e cs_etm/timestamp=1/ -a
 arm_cs_etm_basic_test -e cs_etm/timestamp=0/
 arm_cs_etm_basic_test -e cs_etm/timestamp=1/
 
+arm_cs_etm_sparse_cpus_test
+
 exit $glb_err

-- 
2.34.1