Actually checking the issue in more detail it seems even more that
neither libvirt nor qemu is "it".
Instead many users report similar issues  due to the host grabbing (part
of) the device.
That leads to a conflict then.
So I'd ask to check if any of that applies to your bionic system, maybe
it has a newer or additional driver that does this than what your 17.10
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Installer causes VM to be paused
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