[PATCH] net/mlx5: fix NOP insertion for modify field read-write

[Maayan Kashani <mkashani@nvidia.com>]

In HWS non-root groups, modify field actions are compiled into a
modify header pattern. When a COPY or ADD_FIELD reads a field and the
next SET or ADD writes that same field, no NOP was inserted between
them. Firmware rejects the resulting pattern at template table
creation with syndrome 0xa0a3a8.

flow_hw_should_insert_nop() only compared the new command's
destination with the previous command's destination. After a
COPY or ADD_FIELD it never compared against the previous source
field, which is the one that was read.

Extend the checks so a NOP is inserted when:
- a SET or ADD writes a field read by the previous COPY or ADD_FIELD,
- a COPY or ADD_FIELD writes a field read by the previous COPY or
  ADD_FIELD.

Two consecutive reads of the same field still do not need a NOP.

Fixes: 0f4aa72b99da ("net/mlx5: support flow modify field with HWS")
Cc: stable@dpdk.org

Signed-off-by: Maayan Kashani <mkashani@nvidia.com>
Acked-by: Dariusz Sosnowski <dsosnowski@nvidia.com>
---
 drivers/net/mlx5/mlx5_flow_hw.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/net/mlx5/mlx5_flow_hw.c b/drivers/net/mlx5/mlx5_flow_hw.c
index 8b74f66770b..acbbeb4002f 100644
--- a/drivers/net/mlx5/mlx5_flow_hw.c
+++ b/drivers/net/mlx5/mlx5_flow_hw.c
@@ -1572,7 +1572,8 @@ flow_hw_should_insert_nop(const struct mlx5_hw_modify_header_action *mhdr,
 			should_insert = new_cmd.field == last_cmd.field;
 		else if (last_type == MLX5_MODIFICATION_TYPE_COPY ||
 			 last_type == MLX5_MODIFICATION_TYPE_ADD_FIELD)
-			should_insert = new_cmd.field == last_cmd.dst_field;
+			should_insert = (new_cmd.field == last_cmd.dst_field ||
+					 new_cmd.field == last_cmd.field);
 		else if (last_type == MLX5_MODIFICATION_TYPE_NOP)
 			should_insert = false;
 		else
@@ -1587,7 +1588,8 @@ flow_hw_should_insert_nop(const struct mlx5_hw_modify_header_action *mhdr,
 		else if (last_type == MLX5_MODIFICATION_TYPE_COPY ||
 			 last_type == MLX5_MODIFICATION_TYPE_ADD_FIELD)
 			should_insert = (new_cmd.field == last_cmd.dst_field ||
-					 new_cmd.dst_field == last_cmd.dst_field);
+					 new_cmd.dst_field == last_cmd.dst_field ||
+					 new_cmd.dst_field == last_cmd.field);
 		else if (last_type == MLX5_MODIFICATION_TYPE_NOP)
 			should_insert = false;
 		else
-- 
2.25.1