Re: [PATCH v2 4/4] virtio-net: Add support for USO features

[Akihiko Odaki]

On 2024/08/05 16:30, Michael S. Tsirkin wrote:
> On Sun, Aug 04, 2024 at 03:49:45PM +0900, Akihiko Odaki wrote:
> > I suggest disabling all offload features of virtio-net with 9.2.
>
> Yea ... no.
>
> > I want to keep things consistent so I want to disable all at once. This
> > change will be very uncomfortable for us, who are implementing offload
> > features, but I hope it will motivate us to implement a proper solution.
>
> It's uncomfortable for users.

An obvious alternative is to set cross-migrate=off by default (I dropped 
the no- prefix because no-cross-migrate=off is confusing). I don't have 
a particular idea whether cross-migrate should be on or off by default.

This is a trade-off of safety and performance. In general, I believe 
safety should come first before performance.

On the other hand, disabling offload features is a breaking change. QEMU 
also has -only-migratable option; it is more consistent to make the 
additional assurance for migration opt-in instead of opt-out. Finally, I 
see migration across hosts as an advanced feature, and perhaps it can be 
justified to make it more like an optional feature.

Regards,
Akihiko Odaki