linux-kernel - [PATCH 3/3] perf tests: Skip "test data symbol" on Neoverse N1

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Date: Tue,  9 Apr 2024 09:47:39 +0100
From: James Clark <james.clark@....com>
To: linux-perf-users@...r.kernel.org,
	irogers@...gle.com
Cc: James Clark <james.clark@....com>,
	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>,
	Adrian Hunter <adrian.hunter@...el.com>,
	"Liang, Kan" <kan.liang@...ux.intel.com>,
	Athira Rajeev <atrajeev@...ux.vnet.ibm.com>,
	Leo Yan <leo.yan@...ux.dev>,
	linux-kernel@...r.kernel.org
Subject: [PATCH 3/3] perf tests: Skip "test data symbol" on Neoverse N1

To prevent anyone from seeing a test failure appear as a regression and
thinking that it was caused by their code change, just skip the test on
N1.

It can be caused by any unrelated change that shifts the loop into an
unfortunate position in the Perf binary which is almost impossible to
debug as the root cause of the test failure. Ultimately it's caused by
the referenced errata.

Fixes: 60abedb8aa90 ("perf test: Introduce script for data symbol testing")
Signed-off-by: James Clark <james.clark@....com>
---
 tools/perf/tests/shell/test_data_symbol.sh | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/tools/perf/tests/shell/test_data_symbol.sh b/tools/perf/tests/shell/test_data_symbol.sh
index 3dfa91832aa8..ffc641d00aa4 100755
--- a/tools/perf/tests/shell/test_data_symbol.sh
+++ b/tools/perf/tests/shell/test_data_symbol.sh
@@ -16,6 +16,12 @@ skip_if_no_mem_event() {
 	return 2
 }
 
+# Skip on Arm N1 due to errata 1694299. Bias exists in SPE sampling
+# which can cause the load and store instructions to be skipped
+# entirely. This comes and goes randomly depending on the offset the
+# linker places the datasym loop at in the Perf binary.
+lscpu | grep -q "Neoverse-N1" && exit 2
+
 skip_if_no_mem_event || exit 2
 
 skip_test_missing_symbol buf1
-- 
2.34.1