Re: [Qemu-devel] [PATCH v3 2/2] vhost user: Add RARP injection for legacy guest

[Jason Wang <jasowang@redhat.com>]

On 06/11/2015 01:49 PM, Thibaut Collet wrote:
> > Yes, but still need a mechanism to notify the backend of migration
> > completion from qemu side if GUEST_ANNOUNCE is not negotiated.
>
> backend is aware of a connection with the guest (with the feature
> negociation) and can send a rarp. This rarp will be always sent by the
> backend when a VM is launched (first start or live migration
> completion) if the GUEST_ANOUNCE is not supported.
> In this case the issue is solved without done everything by QEMU.

The issue is during migration guest network is still active. So sending
rarp too early in the destination (e.g during VM is launched) may
confuse the switch.  We want it to be sent exactly when the migration is
completed in destination.

> If sending a rarp message on the start of te VM is not accceptable, we
> must provide a mechanism similar of the one I have implemented. The
> message content can be empty as the backend is able to create the rarp
> message.

Yes.