This is needed to achieve migration, so the destination can restore its
index.
Setting base as last used idx, so destination will see as available all
the entries that the device did not use, including the in-flight
processing ones.
This is ok for networking, but other kinds of devices might have
problems with these retransmissions.
Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>