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

[Michael S. Tsirkin]

On Thu, Aug 01, 2024 at 11:36:19AM -0400, Peter Xu wrote:
> On Thu, Aug 01, 2024 at 01:51:00AM -0400, Michael S. Tsirkin wrote:
> > So I suggest a single command that dumps some description of host
> > features, to be passed to qemu on destination. qemu then fails to
> > start on destination if some of these do not work.
> > The advantage is that this also helps things like -cpu host,
> > and a bunch of other things like vdpa where we like to pass through
> > config from kernel.
> 
> Something like that could work indeed.  I'm thinking whether it shouldn't
> require a new QMP command; that sounds more work, and we also needs Libvirt
> cooperations so QEMU migration will still fail.  I wonder whether we can
> integrate it into migration handshake that I referred previously in our
> TODO item here:
> 
> https://wiki.qemu.org/ToDo/LiveMigration#Migration_handshake

This is different. You can start migration on destination
without touching source at all. This allows e.g. finding
a destination that can support your source.