netdev - Re: regression: UFO removal breaks kvm live migration

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Date:   Wed, 8 Nov 2017 21:53:27 +0900
From:   Jason Wang <jasowang@...hat.com>
To:     David Miller <davem@...emloft.net>
Cc:     willemdebruijn.kernel@...il.com, mkubecek@...e.cz,
        netdev@...r.kernel.org, mst@...hat.com, vyasevic@...hat.com,
        Paolo Bonzini <pbonzini@...hat.com>
Subject: Re: regression: UFO removal breaks kvm live migration



On 2017年11月08日 20:32, David Miller wrote:
> From: Jason Wang <jasowang@...hat.com>
> Date: Wed, 8 Nov 2017 17:25:48 +0900
>
>> On 2017年11月08日 17:08, Willem de Bruijn wrote:
>>> That won't help in the short term. I'm still reading up to see if
>>> there are
>>> any other options besides reimplement or advertise-but-drop, such as
>>> an implicit trigger that would make the guest renegotiate. It's
>>> unlikely, but
>>> worth a look..
>> Yes, this looks hard. And even if we can manage to do this, it looks
>> an overkill since it will impact all guest after migration.
> Like Willem I would much prefer "advertise-but-drop" if it works.

This makes migration work but all guest UFO traffic will stall.

>
> In the long term feature renegotiation triggers are a must.
>
> There is no way for us to remove features otherwise.

We can remove if we don't break userspace(guest).

> In my opinion
> this will even make migrations more powerful.

But this does not help for guest running old version of kernel which  
still think UFO work.

Thanks