The libvirt driver currently does not set the machine type for a KVM guest by default. When not specified, libvirt will use the newest one it knows about. Unfortunately, that can result in live migrations failing if your environment is using different versions of the host OS on compute nodes as the destination node may not be able to support the machine type used when the VM was originally started.
This bugzilla has been removed from the release and needs to be reviewed and Triaged for another Target Release.
Since the problem described in this bug report should be resolved in a recent advisory, it has been closed with a resolution of ERRATA. For information on the advisory, and where to find the updated files, follow the link below. If the solution does not work for you, open a new bug report. https://access.redhat.com/errata/RHBA-2017:2654