netdev - Re: [RFC -next 2/2] virtio_net: Read and use the advised MTU

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Date:	Tue, 15 Mar 2016 16:53:24 -0400
From:	Aaron Conole <aconole@...hat.com>
To:	Sergei Shtylyov <sergei.shtylyov@...entembedded.com>
Cc:	netdev@...r.kernel.org, "Michael S. Tsirkin" <mst@...hat.com>,
	virtualization@...ts.linux-foundation.org,
	linux-kernel@...r.kernel.org
Subject: Re: [RFC -next 2/2] virtio_net: Read and use the advised MTU

Sergei Shtylyov <sergei.shtylyov@...entembedded.com> writes:

> Hello.

Hi Sergei,

> On 03/10/2016 05:28 PM, Aaron Conole wrote:
>
>> This patch checks the feature bit for the VIRTIO_NET_F_MTU feature. If it
>> exists, read the advised MTU and use it.
>>
>> No proper error handling is provided for the case where a user changes the
>> negotiated MTU. A future commit will add proper error handling. Instead, a
>> warning is emitted if the guest changes the device MTU after previously being
>> given advice.
>>
>> Signed-off-by: Aaron Conole <aconole@...hat.com>
>> ---
>>   drivers/net/virtio_net.c | 15 ++++++++++++++-
>>   1 file changed, 14 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
>> index 767ab11..7175563 100644
>> --- a/drivers/net/virtio_net.c
>> +++ b/drivers/net/virtio_net.c
> [...]
>> @@ -1390,8 +1391,12 @@ static const struct ethtool_ops virtnet_ethtool_ops = {
>>
>>   static int virtnet_change_mtu(struct net_device *dev, int new_mtu)
>>   {
>> +	struct virtnet_info *vi = netdev_priv(dev);
>>   	if (new_mtu < MIN_MTU || new_mtu > MAX_MTU)
>>   		return -EINVAL;
>> +	if (vi->negotiated_mtu == true) {
>> +		pr_warn("changing mtu from negotiated mtu.");
>> +	}
>
>    {} not needed, see Documentation/CodingStyle.

Okay, I'll make sure to fix this with v2.

> [...]
>
> MBR, Sergei

Thanks so much for the review!

-Aaron