[PATCH v2 1/2] virtio_net: virtio_net_tx_complete() stop flush new packets for purge operation

[Xuan Zhuo]

For async tx, virtio_net_tx_complete() is called when purge or flush
operation is done. But for purge operation, we should not try to flush
new packet from tx queue. The purge operation means we will stop the
queue soon.

Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
---
 hw/net/virtio-net.c | 32 ++++++++++++++++++--------------
 1 file changed, 18 insertions(+), 14 deletions(-)

diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
index 3ae909041a..6daa1e5ac1 100644
--- a/hw/net/virtio-net.c
+++ b/hw/net/virtio-net.c
@@ -2601,21 +2601,25 @@ static void virtio_net_tx_complete(NetClientState *nc, 
ssize_t len)
     q->async_tx.elem = NULL;
 
     virtio_queue_set_notification(q->tx_vq, 1);
-    ret = virtio_net_flush_tx(q);
-    if (ret >= n->tx_burst) {
-        /*
-         * the flush has been stopped by tx_burst
-         * we will not receive notification for the
-         * remainining part, so re-schedule
-         */
-        virtio_queue_set_notification(q->tx_vq, 0);
-        if (q->tx_bh) {
-            qemu_bh_schedule(q->tx_bh);
-        } else {
-            timer_mod(q->tx_timer,
-                      qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) + n->tx_timeout);
+
+    /* len == 0 means purge, we should not flush new tx packets. */
+    if (len) {
+        ret = virtio_net_flush_tx(q);
+        if (ret >= n->tx_burst) {
+            /*
+             * the flush has been stopped by tx_burst
+             * we will not receive notification for the
+             * remainining part, so re-schedule
+             */
+            virtio_queue_set_notification(q->tx_vq, 0);
+            if (q->tx_bh) {
+                qemu_bh_schedule(q->tx_bh);
+            } else {
+                timer_mod(q->tx_timer,
+                          qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) + 
n->tx_timeout);
+            }
+            q->tx_waiting = 1;
         }
-        q->tx_waiting = 1;
     }
 }
 
-- 
2.32.0.3.g01195cf9f