Yes, exactly. ISCSI-based setup can take some minutes to deploy, given
prepared image, and I have one hundred percent hit rate for the
original issue with it.
I've reproduced your IO hang with 2.0 and both
9b1786829aefb83f37a8f3135e3ea91c56001b56 and
a096b3a6732f846ec57dc28b47ee9435aa0609bf applied.
Reverting 9b1786829aefb83f37a8f3135e3ea91c56001b56 indeed fixes the
problem (but reintroduces block-migration hang). It's seems like qemu
bug rather than guest problem, as no-kvmclock parameters makes no
difference. IO just stops, all qemu IO threads die off. Almost like it
forgets to migrate them:-)
I'm attaching backtrace from guest kernel and qemu and qemu command line.
Going to compile 2.1-rc.