Comment 7 for bug 1888395

Reviewed: https://review.opendev.org/742180
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=b8f3be6b3c5af91d215b4a0cecb9be098e8d8799
Submitter: Zuul
Branch: master

commit b8f3be6b3c5af91d215b4a0cecb9be098e8d8799
Author: root <email address hidden>
Date: Sat Jul 18 00:32:54 2020 -0400

    Set migrate_data.vifs only when using multiple port bindings

    In the rocky cycle nova was enhanced to support the multiple
    port binding live migration workflow when neutron supports
    the binding-extended API extension.
    When the migration_data object was extended to support
    multiple port bindings, populating the vifs field was used
    as a sentinel to indicate that the new workflow should
    be used.

    In the train release
    I734cc01dce13f9e75a16639faf890ddb1661b7eb
    (SR-IOV Live migration indirect port support)
    broke the semantics of the migrate_data object by
    unconditionally populating the vifs field

    This change restores the rocky semantics, which are depended
    on by several parts of the code base, by only conditionally
    populating vifs if neutron supports multiple port bindings.

    Co-Authored-By: Sean Mooney <email address hidden>
    Change-Id: Ia00277ac8a68a635db85f9e0ce2c6d8df396e0d8
    Closes-Bug: #1888395