virtio_net: verify if virtqueue_kick() succeeded

Verify if a host kick succeeded by checking return value of virtqueue_kick().
Signed-off-by: Heinz Graalfs <graalfs@linux.vnet.ibm.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

drivers/net/virtio_net.c

@@ -545,7 +545,8 @@ static bool try_fill_recv(struct receive_queue *rq, gfp_t gfp)
 	} while (rq->vq->num_free);
 	if (unlikely(rq->num > rq->max))
 		rq->max = rq->num;
-	virtqueue_kick(rq->vq);
+	if (unlikely(!virtqueue_kick(rq->vq)))
+		return false;
 	return !oom;
 }
 
@@ -751,7 +752,7 @@ static netdev_tx_t start_xmit(struct sk_buff *skb, struct net_device *dev)
 	err = xmit_skb(sq, skb);
 
 	/* This should not happen! */
-	if (unlikely(err)) {
+	if (unlikely(err) || unlikely(!virtqueue_kick(sq->vq))) {
 		dev->stats.tx_fifo_errors++;
 		if (net_ratelimit())
 			dev_warn(&dev->dev,
@@ -760,7 +761,6 @@ static netdev_tx_t start_xmit(struct sk_buff *skb, struct net_device *dev)
 		kfree_skb(skb);
 		return NETDEV_TX_OK;
 	}
-	virtqueue_kick(sq->vq);
 
 	/* Don't wait up for transmitted skbs to be freed. */
 	skb_orphan(skb);
@@ -819,7 +819,8 @@ static bool virtnet_send_command(struct virtnet_info *vi, u8 class, u8 cmd,
 	BUG_ON(virtqueue_add_sgs(vi->cvq, sgs, out_num, in_num, vi, GFP_ATOMIC)
 	       < 0);
 
-	virtqueue_kick(vi->cvq);
+	if (unlikely(!virtqueue_kick(vi->cvq)))
+		return status == VIRTIO_NET_OK;
 
 	/* Spin for a response, the kick causes an ioport write, trapping
 	 * into the hypervisor, so the request should be handled immediately.