[dpdk-dev] [PATCH] net/mlx4: fix last Tx wqe stamping lack

[Matan Azrad <matan@mellanox.com>]

When Tx pakcet HW processing is done, SW should stamp all the completion
burst WQEs.

Stamp missed last completion burst WQE.

Fixes: c3c977bbecbd ("net/mlx4: add Tx bypassing Verbs")

Signed-off-by: Matan Azrad <matan@mellanox.com>
---
 drivers/net/mlx4/mlx4_rxtx.c | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

I think this is a critical bug fix that should be added to 17.11 version.
No performance impact was seen.

diff --git a/drivers/net/mlx4/mlx4_rxtx.c b/drivers/net/mlx4/mlx4_rxtx.c
index 3985e06..44edeac 100644
--- a/drivers/net/mlx4/mlx4_rxtx.c
+++ b/drivers/net/mlx4/mlx4_rxtx.c
@@ -336,6 +336,7 @@ struct pv {
 {
 	unsigned int elts_comp = txq->elts_comp;
 	unsigned int elts_tail = txq->elts_tail;
+	unsigned int sq_tail = sq->tail;
 	struct mlx4_cq *cq = &txq->mcq;
 	volatile struct mlx4_cqe *cqe;
 	uint32_t cons_index = cq->cons_index;
@@ -372,13 +373,13 @@ struct pv {
 			rte_be_to_cpu_16(cqe->wqe_index) & sq->txbb_cnt_mask;
 		do {
 			/* Free next descriptor. */
-			nr_txbbs +=
+			sq_tail += nr_txbbs;
+			nr_txbbs =
 				mlx4_txq_stamp_freed_wqe(sq,
-				     (sq->tail + nr_txbbs) & sq->txbb_cnt_mask,
-				     !!((sq->tail + nr_txbbs) & sq->txbb_cnt));
+				     sq_tail & sq->txbb_cnt_mask,
+				     !!(sq_tail & sq->txbb_cnt));
 			pkts++;
-		} while (((sq->tail + nr_txbbs) & sq->txbb_cnt_mask) !=
-			 new_index);
+		} while ((sq_tail & sq->txbb_cnt_mask) != new_index);
 		cons_index++;
 	} while (1);
 	if (unlikely(pkts == 0))
@@ -386,7 +387,7 @@ struct pv {
 	/* Update CQ. */
 	cq->cons_index = cons_index;
 	*cq->set_ci_db = rte_cpu_to_be_32(cq->cons_index & MLX4_CQ_DB_CI_MASK);
-	sq->tail = sq->tail + nr_txbbs;
+	sq->tail = sq_tail + nr_txbbs;
 	/* Update the list of packets posted for transmission. */
 	elts_comp -= pkts;
 	assert(elts_comp <= txq->elts_comp);
-- 
1.8.3.1