On Tue, Apr 22, 2014 at 11:53:34AM +0800, Jason Wang wrote:

On 04/22/2014 11:23 AM, Amos Kong wrote:

quoted

On Tue, Apr 22, 2014 at 11:11:50AM +0800, Jason Wang wrote:

quoted

On 04/21/2014 11:11 PM, Amos Kong wrote:

quoted

Currently ethtool returns zero if there is no virtqueue or MQ isn't
support, we should return -ENOTSUPP to notice user.

Signed-off-by: Amos Kong <redacted>

NAK this patch.

quoted

quoted

quoted

---
 drivers/net/virtio_net.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 8a852b5..eaf8266 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c

@@ -1053,7 +1053,7 @@ static int virtnet_set_queues(struct virtnet_info *vi, u16 queue_pairs)
 	struct net_device *dev = vi->dev;
 
 	if (!vi->has_cvq || !virtio_has_feature(vi->vdev, VIRTIO_NET_F_MQ))
-		return 0;
+		return -ENOTSUPP;
 
 	s.virtqueue_pairs = queue_pairs;
 	sg_init_one(&sg, &s, sizeof(s));

How about check the return value of virtnet_set_queues() in
virtnet_restore() also?

If we migrate a guest from MQ supported side to MQ non-supported side,
virtnet_restore() will not return error right now.

If we return error when no vq or no mq support, and check return value
of virtnet_set_queues() in virtnet_restore(), migration will fail. 
Is it expected?

I think what you mean is restore not migration here. The point is not to
execute VIRTIO_NET_CTRL_MQ when multiqueue is not supported, so it's the
caller responsibility to pass a valid queue_pairs to
virtnet_set_queues(). This patch is not necessary, your last patch is
fine enough to solve the issue. Do you agree?

 
Yes.

If mq is supported,
  - change queue to 0: virtnet_send_command() will return error
  - change queue to >= 1: success

If mq isn't support, current queue is 1.
  - change queue to 1: return 0 at mq checking point, nothing is
                       changed, expected.
  * change queue to 0:   we should return -INVAL
    (my first patch checked this in virtnet_set_channels())
  * change queue to > 1: we should return -INVAL
    (we already checked 'queue_pairs > vi->max_queue_pairs' in virtnet_set_channels())

The * items are lack in current virtnet_send_command(), but can
already checked it in virtnet_set_channels(), it's enough.

So we can just apply my first patch [1].

[1] http://www.spinics.net/lists/netdev/msg279631.html

Thanks

Thanks.

BTW, -ENOTSUPP isn't an invalid ERROR for virtio-net.

/* Defined for the NFSv3 protocol */
#define ENOTSUPP        524     /* Operation is not supported */

-- 
			Amos.