Comment 1 for bug 1952745

What do you exactly mean by "Definitions of VMs are removed from libvirt." ?

Which migration are you doing ? I guess cold migrate ? If so, are you confirming the resize or do you have a config option value for it ?

https://docs.openstack.org/api-ref/compute/?expanded=migrate-server-migrate-action-detail#migrate-server-migrate-action

TBH, I don't really see a problem with what you say : if you recreate a nova-compute service, you need to restart it for removing the evacuated instances, but I could maybe misunderstand your concerns.