[openstack][nova] how check if exist instances were create with AZ or without AZ

Hello guys. I need to verify whether an existing instance was created with AZ or without AZ. How can we check on an existing instance? I did not setup default AZ scheduler before. At this time I plan to expand the system by a new AZ. as document If the server was not created in a specific zone then it is free to be moved to other zones, i.e. the AvailabilityZoneFilter <https://docs.openstack.org/nova/latest/admin/scheduling.html#availabilityzonefilter> is a no-op. I am worried about when I migrate instances and they will be free to be moved to other zones. Nguyen Huu Khoi