[libvirt] question about job handling across migration protocol phases

[Jim Fehlig]

While investigating a bug [1] found by Xen's osstest I realized I don't quite 
understand how to handle modify jobs (e.g. BeginJob/EndJob) on virDomainObj 
across the various phases of V3 migration protocol. E.g. on the src host the 
Begin, Perform, and Confirm phases are performed. Should a modify job start 
(BeginJob) in the Begin phase and stop (EndJob) in the Confirm phase? Or should 
each phase, if necessary, do BeginJob/EndJob? Same question for dst host. IMO 
the job should be held across the phases on each host, preventing any 
modifications during the overall migration process. Although I do worry about 
orphaned jobs, e.g. a missed EndJob caused by some obscure error in the 
migration machinery.

Regards,
Jim

[1] https://lists.xenproject.org/archives/html/xen-devel/2018-08/msg01945.html