netdev - Re: virtio_net: can change MTU after installing program

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Message-ID: <d4d65b88-b825-b380-22d2-bc61d50248b4@redhat.com>
Date:   Wed, 26 Feb 2020 13:53:19 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     David Ahern <dahern@...italocean.com>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: virtio_net: can change MTU after installing program


On 2020/2/26 下午12:31, David Ahern wrote:
> On 2/25/20 9:02 PM, Jason Wang wrote:
>>> The simple solution causes a user visible change with 'ip -d li sh' by
>>> showing a changing max mtu, but the ndo has a poor user experience in
>>> that it just fails EINVAL (their is no extack) which is confusing since,
>>> for example, 8192 is a totally legit MTU. Changing the max does return a
>>> nice extack message.
>>
>> Or for simplicity, just forbid changing MTU when program is installed?
> My preference is to show the reduced max MTU when a program is
> installed. Allows the mtu to be increased to the max XDP allows for the
> device.
>

Yes, that's better. But may requires changes in both qemu and virtio 
spec to work.

Do you want to address them? Or if it's not urgent, I can add this in my 
todo list and address it in the future.

Thanks