When guests are terminated, various pieces of cleanup need carrying out.
The cleaning up of PCI devices which were assigned to guests, and the
associated removal of tracking structures for IRQs used by the devices
occurs relatively early in the process.  Unfortunately after that point
the guest about to be terminated could cause its device model (DM) to
re-establish such tracking structures, by having it bind one or more IRQs
anew.  While some of those tracking structures would still be cleaned up
later on, at least one would not be.