Skip to contentSkip to conversation

net/vmxnet3: fix drop of empty segments in tx

PATCH Applied Ronak Doshi 2 participants 2 messages May 9, 2023 – May 18, 2023

Subsystems (2)
lore
Share & tools
lore
#0 lore raw

PATCH v2 1/1 net/vmxnet3: fix drop of empty segments in tx

When empty segments are dropped, some descriptor variable values are updated in the segment processing loop before it is exited. This can lead to a wedged queue where all subsequent packets are dropped for this queue.

Also move the check for empty packet to catch the case of a zero length packet with multiple segments.

Fixes d863f19efa4f ("net/vmxnet3: skip empty segments in transmission")

--
Change log
v2: fixed typo

---
 drivers/net/vmxnet3/vmxnet3_rxtx.c | 33 +++++++++++++++++++--------------
 1 file changed, 19 insertions(+), 14 deletions(-)
drivers/net/vmxnet3/vmxnet3_rxtx.c +19 -14
index a875ffec07..f4cade0954 100644
@@ -412,8 +412,8 @@ vmxnet3_xmit_pkts(void *tx_queue, struct rte_mbuf **tx_pkts,
 
 	nb_tx = 0;
 	while (nb_tx < nb_pkts) {
-		Vmxnet3_GenericDesc *gdesc;
-		vmxnet3_buf_info_t *tbi;
+		Vmxnet3_GenericDesc *gdesc = NULL;
+		vmxnet3_buf_info_t *tbi = NULL;
 		uint32_t first2fill, avail, dw2;
 		struct rte_mbuf *txm = tx_pkts[nb_tx];
 		struct rte_mbuf *m_seg = txm;
@@ -457,18 +457,18 @@ vmxnet3_xmit_pkts(void *tx_queue, struct rte_mbuf **tx_pkts,
 			continue;
 		}
 
+		/* Skip empty packets */
+		if (unlikely(rte_pktmbuf_pkt_len(txm) == 0)) {
+			txq->stats.drop_total++;
+			rte_pktmbuf_free(txm);
+			nb_tx++;
+			continue;
+		}
+
 		if (txm->nb_segs == 1 &&
 		    rte_pktmbuf_pkt_len(txm) <= txq->txdata_desc_size) {
 			struct Vmxnet3_TxDataDesc *tdd;
 
-			/* Skip empty packets */
-			if (unlikely(rte_pktmbuf_pkt_len(txm) == 0)) {
-				txq->stats.drop_total++;
-				rte_pktmbuf_free(txm);
-				nb_tx++;
-				continue;
-			}
-
 			tdd = (struct Vmxnet3_TxDataDesc *)
 				((uint8 *)txq->data_ring.base +
 				 txq->cmd_ring.next2fill *
@@ -481,6 +481,10 @@ vmxnet3_xmit_pkts(void *tx_queue, struct rte_mbuf **tx_pkts,
 		dw2 = (txq->cmd_ring.gen ^ 0x1) << VMXNET3_TXD_GEN_SHIFT;
 		first2fill = txq->cmd_ring.next2fill;
 		do {
+			/* Skip empty segments */
+			if (unlikely(m_seg->data_len == 0))
+				continue;
+
 			/* Remember the transmit buffer for cleanup */
 			tbi = txq->cmd_ring.buf_info + txq->cmd_ring.next2fill;
 
@@ -490,10 +494,6 @@ vmxnet3_xmit_pkts(void *tx_queue, struct rte_mbuf **tx_pkts,
 			 */
 			gdesc = txq->cmd_ring.base + txq->cmd_ring.next2fill;
 
-			/* Skip empty segments */
-			if (unlikely(m_seg->data_len == 0))
-				continue;
-
 			if (copy_size) {
 				uint64 offset =
 					(uint64)txq->cmd_ring.next2fill *
@@ -514,6 +514,11 @@ vmxnet3_xmit_pkts(void *tx_queue, struct rte_mbuf **tx_pkts,
 			/* use the right gen for non-SOP desc */
 			dw2 = txq->cmd_ring.gen << VMXNET3_TXD_GEN_SHIFT;
 		} while ((m_seg = m_seg->next) != NULL);
+		/* We must have executed the complete preceding loop at least
+		 * once without skipping an empty segment, as we can't have
+		 * a packet with only empty segments.
+		 * Thus, tbi and gdesc have been initialized.
+		 */
 
 		/* set the last buf_info for the pkt */
 		tbi->m = txm;
Signature · 1 line
2.11.0
Applied
#1 lore raw
Quoted 5 lines · Ronak Doshi

When empty segments are dropped, some descriptor variable values are updated in the segment processing loop before it is exited. This can lead to a wedged queue where all subsequent packets are dropped for this queue.

Quoted 9 lines

Also move the check for empty packet to catch the case of a zero length packet with multiple segments.

Fixes d863f19efa4f ("net/vmxnet3: skip empty segments in transmission")

Applied to dpdk-next-net/main, thanks.