Comment 2 for bug 1800511

(12:54:52 PM) cfriesen: mriedem: I think the issue is that the instance originally didn't have mtu in it
(12:54:59 PM) cfriesen: then we upgraded nova, and now it would have mtu
(12:55:53 PM) cfriesen: nova on the dest doesn't need to have the mtu, but the xml that we pass the live migration needs to match the xml that was used to start the running instance.

Given that, then yes https://github.com/openstack/nova/commit/2b52cde565d542c03f004b48ee9c1a6a25f5b7cd would have caused the regression since it changed the vif xml config to add the mtu setting which otherwise wasn't in the guest xml when it was last started.