From: Leo Yan <leo.yan@linaro.org>
Date: Mon, 9 Aug 2021 19:14:00 +0800
Subject: coresight: tmc-etr: Add barrier after updating AUX ring buffer

Git-commit: 26701ceb4c2c6bfa5f8c8984fa1a1ea08fa0f02c
Patch-mainline: v5.16-rc1
References: jsc#SLE-19046

Since a memory barrier is required between AUX trace data store and
aux_head store, and the AUX trace data is filled with memcpy(), it's
sufficient to use smp_wmb() so can ensure the trace data is visible
prior to updating aux_head.

Signed-off-by: Leo Yan <leo.yan@linaro.org>
Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Link: https://lore.kernel.org/r/20210809111407.596077-3-leo.yan@linaro.org
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Signed-off-by: Mian Yousaf Kaukab <ykaukab@suse.de>
---
 drivers/hwtracing/coresight/coresight-tmc-etr.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/hwtracing/coresight/coresight-tmc-etr.c b/drivers/hwtracing/coresight/coresight-tmc-etr.c
index 0ac2a611110b..7f4654b72314 100644
--- a/drivers/hwtracing/coresight/coresight-tmc-etr.c
+++ b/drivers/hwtracing/coresight/coresight-tmc-etr.c
@@ -1564,6 +1564,14 @@ tmc_update_etr_buffer(struct coresight_device *csdev,
 	 */
 	if (etr_perf->snapshot)
 		handle->head += size;
+
+	/*
+	 * Ensure that the AUX trace data is visible before the aux_head
+	 * is updated via perf_aux_output_end(), as expected by the
+	 * perf ring buffer.
+	 */
+	smp_wmb();
+
 out:
 	/*
 	 * Don't set the TRUNCATED flag in snapshot mode because 1) the
-- 
2.31.1