Subject: Re: [PATCH net] virtio-net: correctly enable multiqueue

From: "Michael S. Tsirkin" <[email-masked]>
Date: Tue, 13 Dec 2016 15:56:46 +0200

On Tue, Dec 13, 2016 at 02:23:05PM +0800, Jason Wang wrote:
> Commit 4490001029012539937ff02778fe6180613fa949 ("virtio-net: enable
> multiqueue by default") blindly set the affinity instead of queues
> during probe which can cause a mismatch of #queues between guest and
> host. This patch fixes it by setting queues.
> 
> Reported-by: Theodore Ts'o <[email-masked]>
> Tested-by: Theodore Ts'o <[email-masked]>
> Cc: Neil Horman <[email-masked]>
> Cc: Michael S. Tsirkin <[email-masked]>
> Fixes: 49000102901 ("virtio-net: enable multiqueue by default")
> Signed-off-by: Jason Wang <[email-masked]>

Acked-by: Michael S. Tsirkin <[email-masked]>

> ---
>  drivers/net/virtio_net.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index b425fa1..fe9f772 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -1930,7 +1930,9 @@ static int virtnet_probe(struct virtio_device *vdev)
>  		goto free_unregister_netdev;
>  	}
>  
> -	virtnet_set_affinity(vi);
> +	rtnl_lock();
> +	virtnet_set_queues(vi, vi->curr_queue_pairs);
> +	rtnl_unlock();
>  
>  	/* Assume link up if device can't report link status,
>  	   otherwise get link status from config. */

I note that virtnet_set_channels also plays with affinity
directly. Can this be changed to rely on cpu notifiers
somehow?

> -- 
> 2.7.4