Comment 4 for bug 1907522

Quick analysis:

Run that I used for the analysis[1]:

Port binding on the source host before the migration:

Attempting to bind port 0f0f2b61-ea5b-4183-af5e-7c71901283cf on host ubuntu-focal-ovh-bhs1-0022143433 for vnic_type normal with profile {"allocation": "c0328279-3748-5bb9-9c42-1ae95a6f8537"}

Failing port binding on the dest host:

Attempting to bind port 0f0f2b61-ea5b-4183-af5e-7c71901283cf on host ubuntu-focal-ovh-bhs1-0022143424 for vnic_type normal with profile {"allocation": "c0328279-3748-5bb9-9c42-1ae95a6f8537"}

Form this it is clear that nova does not update the "allocation", the RP uuid bandwidth is allocated from, in binding profile when tries to bind the port to the destination host. Therefore neutron does not find the RP on the host the binding points to and therefore the port binding fails.

[1] https://zuul.opendev.org/t/openstack/build/94291078ad4b4df99922be7e41ffdee6/logs