Comment 54 for bug 1815989

it should be noted that post-copy live migration with the force-complete live migration timeout action will signifcatly shorten the time to activate teh dest port binding.

if you are not already using post-copy migration you should change to it to mitgate the delay and in general speed up the live migration.

these are the setting i recommend are used by default for all openstack deployment using libvirt

[libvrirt]
live_migration_permit_post_copy=true
live_migration_timeout_action=force_complete
live_migration_permit_auto_converge=true