netdev - Re: [PATCH] virtio-net: Update the mtu code to match virtio spec

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Message-ID: <20161025194036-mutt-send-email-mst@kernel.org>
Date:   Tue, 25 Oct 2016 19:41:07 +0300
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     Aaron Conole <aconole@...hat.com>
Cc:     netdev@...r.kernel.org, virtualization@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org, Jarod Wilson <jarod@...hat.com>
Subject: Re: [PATCH] virtio-net: Update the mtu code to match virtio spec

On Tue, Oct 25, 2016 at 12:35:35PM -0400, Aaron Conole wrote:
> From: Aaron Conole <aconole@...heb.org>
> 
> The virtio committee recently ratified a change, VIRTIO-152, which
> defines the mtu field to be 'max' MTU, not simply desired MTU.
> 
> This commit brings the virtio-net device in compliance with VIRTIO-152.
> 
> Additionally, drop the max_mtu branch - it cannot be taken since the u16
> returned by virtio_cread16 will never exceed the initial value of
> max_mtu.
> 
> Cc: "Michael S. Tsirkin" <mst@...hat.com>
> Cc: Jarod Wilson <jarod@...hat.com>
> Signed-off-by: Aaron Conole <aconole@...hat.com>

Acked-by: Michael S. Tsirkin <mst@...hat.com>

> ---
>  drivers/net/virtio_net.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 720809f..2cafd12 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -1870,10 +1870,12 @@ static int virtnet_probe(struct virtio_device *vdev)
>  		mtu = virtio_cread16(vdev,
>  				     offsetof(struct virtio_net_config,
>  					      mtu));
> -		if (mtu < dev->min_mtu || mtu > dev->max_mtu)
> +		if (mtu < dev->min_mtu) {
>  			__virtio_clear_bit(vdev, VIRTIO_NET_F_MTU);
> -		else
> +		} else {
>  			dev->mtu = mtu;
> +			dev->max_mtu = mtu;
> +		}
>  	}
>  
>  	if (vi->any_header_sg)
> -- 
> 2.7.4