linux-kernel - [PATCH V2] perf cs-etm: Add fix for coresight trace for any range of CPUs

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Date:   Thu, 20 Apr 2023 22:52:53 -0700
From:   Ganapatrao Kulkarni <gankulkarni@...amperecomputing.com>
To:     linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        mike.leach@...aro.org, suzuki.poulose@....com
Cc:     mathieu.poirier@...aro.org, acme@...nel.org,
        darren@...amperecomputing.com, scott@...amperecomputing.com,
        scclevenger@...amperecomputing.com,
        gankulkarni@...amperecomputing.com
Subject: [PATCH V2] perf cs-etm: Add fix for coresight trace for any range of CPUs

The current implementation supports coresight trace decode for a range
of CPUs, if the first CPU is CPU0.

Perf report segfaults, if tried for sparse CPUs list and also for
any range of CPUs(non zero first CPU).

Adding a fix to perf report for any range of CPUs and for sparse list.

Signed-off-by: Ganapatrao Kulkarni <gankulkarni@...amperecomputing.com>
---

V2:
	Updated with review comments.
	Fixed for sparse list of CPUs also.

V1:
	[1] https://lore.kernel.org/lkml/20230419172101.78638-1-gankulkarni@os.amperecomputing.com/

 tools/perf/util/cs-etm.c | 24 +++++++++++++++++++++++-
 1 file changed, 23 insertions(+), 1 deletion(-)

diff --git a/tools/perf/util/cs-etm.c b/tools/perf/util/cs-etm.c
index 8dd81ddd9e4e..2003717f5779 100644
--- a/tools/perf/util/cs-etm.c
+++ b/tools/perf/util/cs-etm.c
@@ -275,6 +275,25 @@ static int cs_etm__metadata_set_trace_id(u8 trace_chan_id, u64 *cpu_metadata)
 		(typeof(_mask))(((_reg) & (_mask)) >> __bf_shf(_mask)); \
 	})
 
+/*
+ * Get a metadata for a specific cpu from an array.
+ *
+ */
+static u64 *get_cpu_data(struct cs_etm_auxtrace *etm, int cpu)
+{
+	int i;
+	u64 *metadata = NULL;
+
+	for (i = 0; i < etm->num_cpu; i++) {
+		if (etm->metadata[i][CS_ETM_CPU] == (u64)cpu) {
+			metadata = etm->metadata[i];
+			break;
+		}
+	}
+
+	return metadata;
+}
+
 /*
  * Handle the PERF_RECORD_AUX_OUTPUT_HW_ID event.
  *
@@ -344,8 +363,11 @@ static int cs_etm__process_aux_output_hw_id(struct perf_session *session,
 		return 0;
 	}
 
+	cpu_data = get_cpu_data(etm, cpu);
+	if (cpu_data == NULL)
+		return err;
+
 	/* not one we've seen before - lets map it */
-	cpu_data = etm->metadata[cpu];
 	err = cs_etm__map_trace_id(trace_chan_id, cpu_data);
 	if (err)
 		return err;
-- 
2.39.2