You cannot do a live migration while the VM has a modified condition on it. This will cause it halt a migration plan until the VM is stopped.

There are 2 options on dealing with this state:
1. Shut down the VM, do the migration and start it.
2. Shut down and then immediately start the VM, and do a Live Migration.

Option 1 is fairly trivial to implement with the current code. Option will require a bit more work.