net/mlx5: fix overflow of Rx SW ring

If vectorized Rx burst is short of mbufs in replenishment, Rx SW ring can
overflow as the Rx burst handles 4 packets in a loop. This is because the
function fills SW ring and its mbufs first and checks validity of
each completion later. So, there should be some buffer slots at the tail of
the ring to protect mbufs which are already owned by application.

Fixes: 6cb559d67b83 ("net/mlx5: add vectorized Rx/Tx burst for x86")
Cc: stable@dpdk.org
Reported-by: Martin Weiser <martin.weiser@allegro-packets.com>
Signed-off-by: Yongseok Koh <yskoh@mellanox.com>

diff --git a/drivers/net/mlx5/mlx5_rxtx_vec_sse.c b/drivers/net/mlx5/mlx5_rxtx_vec_sse.c
index 33988e3..075dce9 100644 (file)
--- a/drivers/net/mlx5/mlx5_rxtx_vec_sse.c
+++ b/drivers/net/mlx5/mlx5_rxtx_vec_sse.c
@@ -638,6 +638,13 @@ rxq_cq_decompress_v(struct rxq *rxq,
                         offsetof(struct rte_mbuf, rx_descriptor_fields1) + 8);
        RTE_BUILD_BUG_ON(offsetof(struct rte_mbuf, hash) !=
                         offsetof(struct rte_mbuf, rx_descriptor_fields1) + 12);
+       /*
+        * Not to overflow elts array. Decompress next time after mbuf
+        * replenishment.
+        */
+       if (unlikely(mcqe_n + MLX5_VPMD_DESCS_PER_LOOP >
+                    (uint16_t)(rxq->rq_ci - rxq->cq_ci)))
+               return;
        /*
         * A. load mCQEs into a 128bit register.
         * B. store rearm data to mbuf.
@@ -1028,8 +1035,10 @@ rxq_burst_v(struct rxq *rxq, struct rte_mbuf **pkts, uint16_t pkts_n)
        }
        elts_idx = rxq->rq_pi & q_mask;
        elts = &(*rxq->elts)[elts_idx];
-       /* Not to overflow pkts array. */
-       pkts_n = RTE_ALIGN_FLOOR(pkts_n - rcvd_pkt, MLX5_VPMD_DESCS_PER_LOOP);
+       pkts_n = RTE_MIN(pkts_n - rcvd_pkt,
+                        (uint16_t)(rxq->rq_ci - rxq->cq_ci));
+       /* Not to overflow pkts/elts array. */
+       pkts_n = RTE_ALIGN_FLOOR(pkts_n, MLX5_VPMD_DESCS_PER_LOOP);
        /* Not to cross queue end. */
        pkts_n = RTE_MIN(pkts_n, q_n - elts_idx);
        if (!pkts_n)