Hello, the issue is not specific to the iothread code because generic virtio-blk also hangs up:
Given code set like in the http://www.mail-archive.com/qemu-devel@nongnu.org/msg246164.html, launch a VM with virtio-blk disk and writeback rbd backend, fire up fio, migrate once with libvirt: time virsh migrate vm27842 qemu+tcp://10.6.0.10/system --live --persistent --undefinesource --timeout 60 real 1m2.969s user 0m0.016s sys 0m0.008s For ones who are unfamiliar with libvirt syntax this means that the live migration was failed to complete over sixty seconds, VM was frozen, moved and re-launched at the destination. After this, I/O gets stuck forever. Any diagnostic information is available upon request if there will be difficulties repeating the issue.
