netdev - Re: [PATCH net V2] virtio-net: set queues after driver

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Message-ID: <df77249e-3ac1-e933-fdfb-464f37a19df6@gmail.com>
Date: Mon, 21 Aug 2023 15:54:53 +0800
From: Like Xu <like.xu.linux@...il.com>
To: Jason Wang <jasowang@...hat.com>,
 "Michael S.Tsirkin, Red Hat" <mst@...hat.com>
Cc: netdev@...r.kernel.org, virtualization@...ts.linux-foundation.org,
 edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com,
 davem@...emloft.net, xuanzhuo@...ux.alibaba.com
Subject: Re: [PATCH net V2] virtio-net: set queues after driver_ok

On 10/8/2023 11:12 am, Jason Wang wrote:
> Commit 25266128fe16 ("virtio-net: fix race between set queues and
> probe") tries to fix the race between set queues and probe by calling
> _virtnet_set_queues() before DRIVER_OK is set. This violates virtio
> spec. Fixing this by setting queues after virtio_device_ready().
> 
> Note that rtnl needs to be held for userspace requests to change the
> number of queues. So we are serialized in this way.
> 
> Fixes: 25266128fe16 ("virtio-net: fix race between set queues and probe")
> Reported-by: Dragos Tatulea <dtatulea@...dia.com>

I had the same issue to report and this fix helped me out.
Tested-by: Like Xu <likexu@...cent.com>

> Acked-by: Michael S. Tsirkin <mst@...hat.com>
> Signed-off-by: Jason Wang <jasowang@...hat.com>
> ---
> The patch is needed for -stable.
> Changes since V1: Tweak the commit log.
> ---
>   drivers/net/virtio_net.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 1270c8d23463..ff03921e46df 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -4219,8 +4219,6 @@ static int virtnet_probe(struct virtio_device *vdev)
>   	if (vi->has_rss || vi->has_rss_hash_report)
>   		virtnet_init_default_rss(vi);
>   
> -	_virtnet_set_queues(vi, vi->curr_queue_pairs);
> -
>   	/* serialize netdev register + virtio_device_ready() with ndo_open() */
>   	rtnl_lock();
>   
> @@ -4233,6 +4231,8 @@ static int virtnet_probe(struct virtio_device *vdev)
>   
>   	virtio_device_ready(vdev);
>   
> +	_virtnet_set_queues(vi, vi->curr_queue_pairs);
> +
>   	/* a random MAC address has been assigned, notify the device.
>   	 * We don't fail probe if VIRTIO_NET_F_CTRL_MAC_ADDR is not there
>   	 * because many devices work fine without getting MAC explicitly