Re: [RFC] VIRTIO_F_IO_BARRIER: use I/O barriers in driver

[Paolo Bonzini <pbonzini@redhat.com>]

On 25/04/2018 16:29, Michael S. Tsirkin wrote:
>> Unfortunately this doesn't work as mentioned earlier.  Virtio live
>> migration assumes that features are safe if you have them on the
>> destination but not on the source; this feature however works the
>> opposite way.
>
> That's a qemu code property, and it's because it does not
> migrate host properties right now. When implementing this feature we
> can add migration of host features.

You don't even need to migrate host features; it's just that guest
feature negotiation is repeated on the destination, and live migration
reports an error if the negotiation fails.  The guest feature
negotiation is complicated a little bit by this feature, but I guess it
can work...

Paolo