[dpdk-dev] [PATCH v4 3/4] net/af_xdp: make reserve/submit peek/release consistent

[Xiaolong Ye]

As David pointed out, if we reserve N slots for Tx, but only submit n
slots, we would end up with an incorrect opinion of the number of available
slots later, we also would get wrong idx when we call
xsk_ring_prod__reserve next time. It also applies to
xsk_ring_cons__peek()/xsk_ring_cons__release().

This patch ensures that both reserve/submit and peek/release are
consistent.

Fixes: f1debd77efaf ("net/af_xdp: introduce AF_XDP PMD")

Suggested-by: David Marchand <david.marchand at redhat.com>
Reviewed-by: David Marchand <david.marchand at redhat.com>
Signed-off-by: Xiaolong Ye <xiaolong.ye at intel.com>
---
 drivers/net/af_xdp/rte_eth_af_xdp.c | 79 +++++++++++++++--------------
 1 file changed, 40 insertions(+), 39 deletions(-)

diff --git a/drivers/net/af_xdp/rte_eth_af_xdp.c b/drivers/net/af_xdp/rte_eth_af_xdp.c
index c46916bbe..6a0096523 100644
--- a/drivers/net/af_xdp/rte_eth_af_xdp.c
+++ b/drivers/net/af_xdp/rte_eth_af_xdp.c
@@ -134,30 +134,34 @@ static const struct rte_eth_link pmd_link = {
 };
 
 static inline int
-reserve_fill_queue(struct xsk_umem_info *umem, int reserve_size)
+reserve_fill_queue(struct xsk_umem_info *umem, uint16_t reserve_size)
 {
 	struct xsk_ring_prod *fq = &umem->fq;
+	void *addrs[reserve_size];
 	uint32_t idx;
-	int i, ret;
+	uint16_t i;
+
+	if (rte_ring_dequeue_bulk(umem->buf_ring, addrs, reserve_size, NULL)
+		    != reserve_size) {
+		AF_XDP_LOG(DEBUG, "Failed to get enough buffers for fq.\n");
+		return -1;
+	}
 
-	ret = xsk_ring_prod__reserve(fq, reserve_size, &idx);
-	if (unlikely(!ret)) {
-		AF_XDP_LOG(ERR, "Failed to reserve enough fq descs.\n");
-		return ret;
+	if (unlikely(!xsk_ring_prod__reserve(fq, reserve_size, &idx))) {
+		AF_XDP_LOG(DEBUG, "Failed to reserve enough fq descs.\n");
+		rte_ring_enqueue_bulk(umem->buf_ring, addrs,
+				reserve_size, NULL);
+		return -1;
 	}
 
 	for (i = 0; i < reserve_size; i++) {
 		__u64 *fq_addr;
-		void *addr = NULL;
-		if (rte_ring_dequeue(umem->buf_ring, &addr)) {
-			i--;
-			break;
-		}
+
 		fq_addr = xsk_ring_prod__fill_addr(fq, idx++);
-		*fq_addr = (uint64_t)addr;
+		*fq_addr = (uint64_t)addrs[i];
 	}
 
-	xsk_ring_prod__submit(fq, i);
+	xsk_ring_prod__submit(fq, reserve_size);
 
 	return 0;
 }
@@ -174,21 +178,20 @@ eth_af_xdp_rx(void *queue, struct rte_mbuf **bufs, uint16_t nb_pkts)
 	struct rte_mbuf *mbufs[ETH_AF_XDP_TX_BATCH_SIZE];
 	unsigned long dropped = 0;
 	unsigned long rx_bytes = 0;
-	uint16_t count = 0;
 	int rcvd, i;
 
 	nb_pkts = RTE_MIN(nb_pkts, ETH_AF_XDP_TX_BATCH_SIZE);
 
+	if (unlikely(rte_pktmbuf_alloc_bulk(rxq->mb_pool, mbufs, nb_pkts) != 0))
+		return 0;
+
 	rcvd = xsk_ring_cons__peek(rx, nb_pkts, &idx_rx);
 	if (rcvd == 0)
-		return 0;
+		goto out;
 
 	if (xsk_prod_nb_free(fq, free_thresh) >= free_thresh)
 		(void)reserve_fill_queue(umem, ETH_AF_XDP_RX_BATCH_SIZE);
 
-	if (unlikely(rte_pktmbuf_alloc_bulk(rxq->mb_pool, mbufs, rcvd) != 0))
-		return 0;
-
 	for (i = 0; i < rcvd; i++) {
 		const struct xdp_desc *desc;
 		uint64_t addr;
@@ -204,7 +207,7 @@ eth_af_xdp_rx(void *queue, struct rte_mbuf **bufs, uint16_t nb_pkts)
 		rte_pktmbuf_pkt_len(mbufs[i]) = len;
 		rte_pktmbuf_data_len(mbufs[i]) = len;
 		rx_bytes += len;
-		bufs[count++] = mbufs[i];
+		bufs[i] = mbufs[i];
 
 		rte_ring_enqueue(umem->buf_ring, (void *)addr);
 	}
@@ -215,7 +218,12 @@ eth_af_xdp_rx(void *queue, struct rte_mbuf **bufs, uint16_t nb_pkts)
 	rxq->stats.rx_pkts += (rcvd - dropped);
 	rxq->stats.rx_bytes += rx_bytes;
 
-	return count;
+out:
+	if (rcvd != nb_pkts)
+		rte_mempool_put_bulk(rxq->mb_pool, (void **)&mbufs[rcvd],
+				     nb_pkts - rcvd);
+
+	return rcvd;
 }
 
 static void
@@ -262,7 +270,7 @@ eth_af_xdp_tx(void *queue, struct rte_mbuf **bufs, uint16_t nb_pkts)
 	struct rte_mbuf *mbuf;
 	void *addrs[ETH_AF_XDP_TX_BATCH_SIZE];
 	unsigned long tx_bytes = 0;
-	int i, valid = 0;
+	int i;
 	uint32_t idx_tx;
 
 	nb_pkts = RTE_MIN(nb_pkts, ETH_AF_XDP_TX_BATCH_SIZE);
@@ -283,20 +291,18 @@ eth_af_xdp_tx(void *queue, struct rte_mbuf **bufs, uint16_t nb_pkts)
 	for (i = 0; i < nb_pkts; i++) {
 		struct xdp_desc *desc;
 		void *pkt;
-		uint32_t buf_len = ETH_AF_XDP_FRAME_SIZE
-					- ETH_AF_XDP_DATA_HEADROOM;
+
 		desc = xsk_ring_prod__tx_desc(&txq->tx, idx_tx + i);
 		mbuf = bufs[i];
-		if (mbuf->pkt_len <= buf_len) {
-			desc->addr = (uint64_t)addrs[valid];
-			desc->len = mbuf->pkt_len;
-			pkt = xsk_umem__get_data(umem->mz->addr,
-						 desc->addr);
-			rte_memcpy(pkt, rte_pktmbuf_mtod(mbuf, void *),
-			       desc->len);
-			valid++;
-			tx_bytes += mbuf->pkt_len;
-		}
+
+		desc->addr = (uint64_t)addrs[i];
+		desc->len = mbuf->pkt_len;
+		pkt = xsk_umem__get_data(umem->mz->addr,
+					 desc->addr);
+		rte_memcpy(pkt, rte_pktmbuf_mtod(mbuf, void *),
+			   desc->len);
+		tx_bytes += mbuf->pkt_len;
+
 		rte_pktmbuf_free(mbuf);
 	}
 
@@ -304,12 +310,7 @@ eth_af_xdp_tx(void *queue, struct rte_mbuf **bufs, uint16_t nb_pkts)
 
 	kick_tx(txq);
 
-	if (valid < nb_pkts)
-		rte_ring_enqueue_bulk(umem->buf_ring, &addrs[valid],
-				 nb_pkts - valid, NULL);
-
-	txq->stats.err_pkts += nb_pkts - valid;
-	txq->stats.tx_pkts += valid;
+	txq->stats.tx_pkts += nb_pkts;
 	txq->stats.tx_bytes += tx_bytes;
 
 	return nb_pkts;
-- 
2.17.1