Description of problem:
A disk driver definition using iothread parameter causes live migration with copy storage to hang during or just before the final ram sync stage.
Interestingly, having the scsi controller as a separate iothread does not trigger the issue.
Version-Release number of selected component (if applicable):
I can reproduce this on centos7 with qemu-ev and with centos 8:
Steps to Reproduce:
1. Create a definition with 1 iothread on the disk image:
<driver name='qemu' type='qcow2' iothread='1' />
2. Issue a live migrate request like: virsh migrate --live --copy-storage-all vm qemu+tcp://remote/system
3. Live migrate on source copies storage and then hangs at 80-99%, I guess during the ram copy phase.
Keeping exactly the same config but without the iothread on the disk driver has successful migrations every time.
There are few problems with iothreads and block jobs being solved in qemu upstream.
Unfortunately the QEMU upstream bug tracking is not handled in this bugzilla instance but at
I will close this bug since I can't move it to qemu. Please report it to the qemu team.