[dpdk-stable] [PATCH 2/3] net/virtio: fix segmented packet issue in mergeable Rx path

[Maxime Coquelin <maxime.coquelin@redhat.com>]

After having dequeued a burst of descriptors, there may be a
need to dequeue a few more if the last packet was segmented
and not complete.

When it happens, the extra segments were not properly attached
to the mbuf chain, and so were lost.

This patch fixes the mbuf chaining.

Fixes: bcac5aa207f8 ("net/virtio: improve batching in mergeable path")
Cc: stable@dpdk.org

Reported-by: Yaroslav Brustinov <ybrustin@cisco.com>
Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>

Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
---
 drivers/net/virtio/virtio_rxtx.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/net/virtio/virtio_rxtx.c b/drivers/net/virtio/virtio_rxtx.c
index 6e76596e56..901490217c 100644
--- a/drivers/net/virtio/virtio_rxtx.c
+++ b/drivers/net/virtio/virtio_rxtx.c
@@ -1615,7 +1615,7 @@ virtio_recv_mergeable_pkts(void *rx_queue,
 	struct virtqueue *vq = rxvq->vq;
 	struct virtio_hw *hw = vq->hw;
 	struct rte_mbuf *rxm;
-	struct rte_mbuf *prev;
+	struct rte_mbuf *prev = NULL;
 	uint16_t nb_used, num, nb_rx = 0;
 	uint32_t len[VIRTIO_MBUF_BURST_SZ];
 	struct rte_mbuf *rcv_pkts[VIRTIO_MBUF_BURST_SZ];
@@ -1722,7 +1722,6 @@ virtio_recv_mergeable_pkts(void *rx_queue,
 		uint16_t rcv_cnt = RTE_MIN((uint16_t)seg_res,
 					VIRTIO_MBUF_BURST_SZ);
 
-		prev = rcv_pkts[nb_rx];
 		if (likely(VIRTQUEUE_NUSED(vq) >= rcv_cnt)) {
 			virtio_rmb(hw->weak_barriers);
 			num = virtqueue_dequeue_burst_rx(vq, rcv_pkts, len,
-- 
2.21.0