[PATCH RESEND 08/13] net/hns3: fix next-to-use overflow when using simple xmit

[Dongdong Liu]

From: Chengwen Feng <fengchengwen at huawei.com>

If txq's next-to-use plus nb_pkts equal txq's nb_tx_desc when using
simple xmit algorithm, the txq's next-to-use will equal nb_tx_desc
fter the xmit, this does not cause Tx exceptions, but may affect other
ops that depend on this field, such as tx_descriptor_status.

This patch fixes it.

Fixes: 7ef933908f04 ("net/hns3: add simple Tx path")
Cc: stable at dpdk.org

Signed-off-by: Chengwen Feng <fengchengwen at huawei.com>
Signed-off-by: Dongdong Liu <liudongdong3 at huawei.com>
---
 drivers/net/hns3/hns3_rxtx.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/net/hns3/hns3_rxtx.c b/drivers/net/hns3/hns3_rxtx.c
index 731f1bc0ef..1b1dc6b8e4 100644
--- a/drivers/net/hns3/hns3_rxtx.c
+++ b/drivers/net/hns3/hns3_rxtx.c
@@ -4126,14 +4126,16 @@ hns3_xmit_pkts_simple(void *tx_queue,
 	}
 
 	txq->tx_bd_ready -= nb_pkts;
-	if (txq->next_to_use + nb_pkts > txq->nb_tx_desc) {
+	if (txq->next_to_use + nb_pkts >= txq->nb_tx_desc) {
 		nb_tx = txq->nb_tx_desc - txq->next_to_use;
 		hns3_tx_fill_hw_ring(txq, tx_pkts, nb_tx);
 		txq->next_to_use = 0;
 	}
 
-	hns3_tx_fill_hw_ring(txq, tx_pkts + nb_tx, nb_pkts - nb_tx);
-	txq->next_to_use += nb_pkts - nb_tx;
+	if (nb_pkts > nb_tx) {
+		hns3_tx_fill_hw_ring(txq, tx_pkts + nb_tx, nb_pkts - nb_tx);
+		txq->next_to_use += nb_pkts - nb_tx;
+	}
 
 	hns3_write_txq_tail_reg(txq, nb_pkts);
 
-- 
2.22.0