virtio: reset function

A reset function solves three problems:

1) It allows us to renegotiate features, eg. if we want to upgrade a
   guest driver without rebooting the guest.

2) It gives us a clean way of shutting down virtqueues: after a reset,
   we know that the buffers won't be used by the host, and

3) It helps the guest recover from messed-up drivers.

So we remove the ->shutdown hook, and the only way we now remove
feature bits is via reset.

We leave it to the driver to do the reset before it deletes queues:
the balloon driver, for example, needs to chat to the host in its
remove function.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

1 files changed, 3 insertions, 2 deletions

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index ec43284ffd13..6e0a9fefe6cb 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -390,13 +390,14 @@ static void virtnet_remove(struct virtio_device *vdev)
 	struct virtnet_info *vi = vdev->priv;
 	struct sk_buff *skb;
 
+	/* Stop all the virtqueues. */
+	vdev->config->reset(vdev);
+
 	/* Free our skbs in send and recv queues, if any. */
-	vi->rvq->vq_ops->shutdown(vi->rvq);
 	while ((skb = __skb_dequeue(&vi->recv)) != NULL) {
 		kfree_skb(skb);
 		vi->num--;
 	}
-	vi->svq->vq_ops->shutdown(vi->svq);
 	while ((skb = __skb_dequeue(&vi->send)) != NULL)
 		kfree_skb(skb);