The issue is described in detail at https://issues.redhat.com/browse/CNV-64444?focusedId=27534057#comment-27534057 and https://passt.top/passt/commit/?id=a8782865c342eb2682cca292d5bf92b567344351.

This is to track the implementation of the workaround / fix in passt itself: we concluded that the only reasonable solution, at least in the short term, is to keep passt around on the source node even after migration completes, and even after QEMU terminates.

We'll need to backport upstream commit a8782865c342 ("treewide: By default, don't quit source after migration, keep sockets open").