[PATCH v3] net/mlx5: fix assert on getting register of sample flow

[Jiawei Wang <jiaweiw@nvidia.com>]

The sample flow tried to get the reserved metadata register for
match implicitly, and if the reserved metadata register was invalid
then back to use the application tag.

The assertion failure was caused while getting register due to
the reserved metadata regC is invalid on CX-5 trusted device(VF/SF).

This patch adds the checking for reserved metadata register before
getting the register, to avoid assertion failure.

Fixes: 9a726360dd30 ("net/mlx5: fix sample flow action on trusted device")
Cc: stable@dpdk.org

Signed-off-by: Jiawei Wang <jiaweiw@nvidia.com>
Acked-by: Viacheslav Ovsiienko <viacheslavo@nvidia.com>
---
v2: fix commit mailmap issue
v3: fix commit mailmap issue
---
 drivers/net/mlx5/mlx5_flow.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/net/mlx5/mlx5_flow.c b/drivers/net/mlx5/mlx5_flow.c
index a0cf677fb0..1768ec3cdb 100644
--- a/drivers/net/mlx5/mlx5_flow.c
+++ b/drivers/net/mlx5/mlx5_flow.c
@@ -6125,13 +6125,14 @@ flow_sample_split_prep(struct rte_eth_dev *dev,
 		/* Prepare the prefix tag action. */
 		append_index++;
 		set_tag = (void *)(actions_pre + actions_n + append_index);
-		ret = mlx5_flow_get_reg_id(dev, MLX5_SAMPLE_ID, 0, error);
 		/* Trust VF/SF on CX5 not supported meter so that the reserved
 		 * metadata regC is REG_NON, back to use application tag
 		 * index 0.
 		 */
-		if (unlikely(ret == REG_NON))
+		if (unlikely(priv->mtr_color_reg == REG_NON))
 			ret = mlx5_flow_get_reg_id(dev, MLX5_APP_TAG, 0, error);
+		else
+			ret = mlx5_flow_get_reg_id(dev, MLX5_SAMPLE_ID, 0, error);
 		if (ret < 0)
 			return ret;
 		mlx5_ipool_malloc(priv->sh->ipool
-- 
2.18.1