[PATCH v3] net/mlx5: use just sufficient barrier for ARM platforms

[Honnappa Nagarahalli]

cqe->op_own indicates if the CQE is owned by the NIC. The rest of
the fields in CQE should be read only after op_own is read. On Arm
platforms using "dmb ishld" is sufficient to enforce this.

Fixes: 88c0733535d6 ("net/mlx5: extend Rx completion with error handling")
Cc: matan at mellanox.com
Cc: stable at dpdk.org

Signed-off-by: Honnappa Nagarahalli <honnappa.nagarahalli at arm.com>
Reviewed-by: Ruifeng Wang <ruifeng.wang at arm.com>
---
 drivers/common/mlx5/mlx5_common.h | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/common/mlx5/mlx5_common.h b/drivers/common/mlx5/mlx5_common.h
index f8d07d6c6b..f4ddaf9f11 100644
--- a/drivers/common/mlx5/mlx5_common.h
+++ b/drivers/common/mlx5/mlx5_common.h
@@ -203,7 +203,11 @@ check_cqe(volatile struct mlx5_cqe *cqe, const uint16_t cqes_n,
 
 	if (unlikely((op_owner != (!!(idx))) || (op_code == MLX5_CQE_INVALID)))
 		return MLX5_CQE_STATUS_HW_OWN;
-	rte_io_rmb();
+	/* Prevent speculative reading of other fields in CQE until
+	 * CQE is valid.
+	 */
+	rte_atomic_thread_fence(__ATOMIC_ACQUIRE);
+
 	if (unlikely(op_code == MLX5_CQE_RESP_ERR ||
 		     op_code == MLX5_CQE_REQ_ERR))
 		return MLX5_CQE_STATUS_ERR;
-- 
2.25.1