Comment 6 for bug 1550400

This one seems doable: "#1 Solve it in Nova pre live migration" ...we should reach a general consensus, as you mention if might not work properly with all the mech drivers.
#3 and #4 solve only some specific use-case so I'd avoid it.

Regarding preventing invalid migration, #1 could work if the handle the migration the same way we handle port creation. Nova should wait for some Neutron event before declaring the migration successful. If it fails the migration should be reverted somehow, for example blocking all the traffic for the instance and setting it in error state.
Anyway I think we should move this conversation in the ML so that we can involve as many people as possible. Thanks for the nice write-up!