[dpdk-dev] [PATCH] net/af_xdp: fix zero copy Tx queue drain

[Baruch Siach <baruch@tkos.co.il>]

Call xsk_ring_prod__submit() before kick_tx() so that the kernel
consumer sees the updated state of Tx ring. Otherwise, Tx packets are
stuck in the ring until the next call to af_xdp_tx_zc().

Fixes: d8a210774e1d ("net/af_xdp: support unaligned umem chunks")
Cc: stable@dpdk.org

Signed-off-by: Baruch Siach <baruch@tkos.co.il>
---
 drivers/net/af_xdp/rte_eth_af_xdp.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/net/af_xdp/rte_eth_af_xdp.c b/drivers/net/af_xdp/rte_eth_af_xdp.c
index 74ffa4511284..81998d86b4aa 100644
--- a/drivers/net/af_xdp/rte_eth_af_xdp.c
+++ b/drivers/net/af_xdp/rte_eth_af_xdp.c
@@ -502,10 +502,11 @@ af_xdp_tx_zc(void *queue, struct rte_mbuf **bufs, uint16_t nb_pkts)
 
 		if (mbuf->pool == umem->mb_pool) {
 			if (!xsk_ring_prod__reserve(&txq->tx, 1, &idx_tx)) {
+				xsk_ring_prod__submit(&txq->tx, count);
 				kick_tx(txq, cq);
 				if (!xsk_ring_prod__reserve(&txq->tx, 1,
 							    &idx_tx))
-					goto out;
+					goto out_skip_tx;
 			}
 			desc = xsk_ring_prod__tx_desc(&txq->tx, idx_tx);
 			desc->len = mbuf->pkt_len;
@@ -527,7 +528,6 @@ af_xdp_tx_zc(void *queue, struct rte_mbuf **bufs, uint16_t nb_pkts)
 
 			if (!xsk_ring_prod__reserve(&txq->tx, 1, &idx_tx)) {
 				rte_pktmbuf_free(local_mbuf);
-				kick_tx(txq, cq);
 				goto out;
 			}
 
@@ -551,11 +551,11 @@ af_xdp_tx_zc(void *queue, struct rte_mbuf **bufs, uint16_t nb_pkts)
 		tx_bytes += mbuf->pkt_len;
 	}
 
-	kick_tx(txq, cq);
-
 out:
 	xsk_ring_prod__submit(&txq->tx, count);
+	kick_tx(txq, cq);
 
+out_skip_tx:
 	txq->stats.tx_pkts += count;
 	txq->stats.tx_bytes += tx_bytes;
 	txq->stats.tx_dropped += nb_pkts - count;
-- 
2.32.0