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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: qemu-kvm-ev-2.12.0-33.1.el7_7.4.x86_64 qemu-kvm-2.12.0-65.module_el8.0.0+189+f9babebb.5.x86_64 How reproducible: Always 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. Additional info:
There are few problems with iothreads and block jobs being solved in qemu upstream. https://lists.gnu.org/archive/html/qemu-devel/2020-01/msg01440.html Unfortunately the QEMU upstream bug tracking is not handled in this bugzilla instance but at https://bugs.launchpad.net/qemu/ I will close this bug since I can't move it to qemu. Please report it to the qemu team.