From a779ba05d470f533f7d8b25b570bacbecb01a88d Mon Sep 17 00:00:00 2001 From: Ouyang Changchun Date: Wed, 15 Oct 2014 11:11:00 +0800 Subject: [PATCH] virtio: fix needed vring entry number Fix one issue in virtio TX: it needs one more vring descriptor to hold the virtio header when transmitting packets, it is used later to determine whether to free more entries from used vring. It fixes failing to transmit any packet with 1 segment in the circumstance of only 1 descriptor in the vring free list. Signed-off-by: Changchun Ouyang Reviewed-by: Olivier Matz --- lib/librte_pmd_virtio/virtio_rxtx.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) diff --git a/lib/librte_pmd_virtio/virtio_rxtx.c b/lib/librte_pmd_virtio/virtio_rxtx.c index ad6401c97a..3f6bad283d 100644 --- a/lib/librte_pmd_virtio/virtio_rxtx.c +++ b/lib/librte_pmd_virtio/virtio_rxtx.c @@ -699,7 +699,8 @@ virtio_xmit_pkts(void *tx_queue, struct rte_mbuf **tx_pkts, uint16_t nb_pkts) num = (uint16_t)(likely(nb_used < VIRTIO_MBUF_BURST_SZ) ? nb_used : VIRTIO_MBUF_BURST_SZ); while (nb_tx < nb_pkts) { - int need = tx_pkts[nb_tx]->nb_segs - txvq->vq_free_cnt; + /* Need one more descriptor for virtio header. */ + int need = tx_pkts[nb_tx]->nb_segs - txvq->vq_free_cnt + 1; int deq_cnt = RTE_MIN(need, (int)num); num -= (deq_cnt > 0) ? deq_cnt : 0; @@ -708,7 +709,12 @@ virtio_xmit_pkts(void *tx_queue, struct rte_mbuf **tx_pkts, uint16_t nb_pkts) deq_cnt--; } - if (tx_pkts[nb_tx]->nb_segs <= txvq->vq_free_cnt) { + need = (int)tx_pkts[nb_tx]->nb_segs - txvq->vq_free_cnt + 1; + /* + * Zero or negative value indicates it has enough free + * descriptors to use for transmitting. + */ + if (likely(need <= 0)) { txm = tx_pkts[nb_tx]; /* Enqueue Packet buffers */ error = virtqueue_enqueue_xmit(txvq, txm); -- 2.20.1