commit 3f257538798b48dd727e79c8af6b2a11bd502e5b
Author: Bryan Venteicher <bryanv@daemoninthecloset.org>
Date:   Tue Feb 4 00:08:52 2014 -0600

    Simulate an interrupt if the watchdog drained the Tx complete queue

diff --git a/sys/dev/virtio/network/if_vtnet.c b/sys/dev/virtio/network/if_vtnet.c
index cc4adeb..93de504 100644
--- a/sys/dev/virtio/network/if_vtnet.c
+++ b/sys/dev/virtio/network/if_vtnet.c
@@ -149,7 +149,7 @@ static void	vtnet_txq_tq_deferred(void *, int);
 #endif
 static void	vtnet_txq_start(struct vtnet_txq *);
 static void	vtnet_txq_tq_intr(void *, int);
-static void	vtnet_txq_eof(struct vtnet_txq *);
+static int	vtnet_txq_eof(struct vtnet_txq *);
 static void	vtnet_tx_vq_intr(void *);
 static void	vtnet_tx_start_all(struct vtnet_softc *);
 
@@ -2385,18 +2385,21 @@ vtnet_txq_tq_intr(void *xtxq, int pending)
 	VTNET_TXQ_UNLOCK(txq);
 }
 
-static void
+static int
 vtnet_txq_eof(struct vtnet_txq *txq)
 {
 	struct virtqueue *vq;
 	struct vtnet_tx_header *txhdr;
 	struct mbuf *m;
+	int deq;
 
 	vq = txq->vtntx_vq;
+	deq = 0;
 	VTNET_TXQ_LOCK_ASSERT(txq);
 
 	while ((txhdr = virtqueue_dequeue(vq, NULL)) != NULL) {
 		m = txhdr->vth_mbuf;
+		deq++;
 
 		txq->vtntx_stats.vtxs_opackets++;
 		txq->vtntx_stats.vtxs_obytes += m->m_pkthdr.len;
@@ -2409,6 +2412,8 @@ vtnet_txq_eof(struct vtnet_txq *txq)
 
 	if (virtqueue_empty(vq))
 		txq->vtntx_watchdog = 0;
+
+	return (deq);
 }
 
 static void
@@ -2512,8 +2517,13 @@ vtnet_watchdog(struct vtnet_txq *txq)
 	sc = txq->vtntx_sc;
 
 	VTNET_TXQ_LOCK(txq);
-	if (sc->vtnet_flags & VTNET_FLAG_EVENT_IDX)
-		vtnet_txq_eof(txq);
+	if (sc->vtnet_flags & VTNET_FLAG_EVENT_IDX) {
+		if (txq->vtntx_watchdog != 0 && vtnet_txq_eof(txq) != 0) {
+			taskqueue_enqueue(txq->vtntx_tq, &txq->vtntx_intrtask);
+			VTNET_TXQ_UNLOCK(txq);
+			return (0);
+		}
+	}
 	if (txq->vtntx_watchdog == 0 || --txq->vtntx_watchdog) {
 		VTNET_TXQ_UNLOCK(txq);
 		return (0);