Downgrading qemu on Ubuntu 17.10

I have been happily running qemu-system-x86_64 to create a virtual machine over the past 3 years, but it looks like the upgrade to Ubuntu 17.10 broke my virtual machine, as it falls into an infinite boot loop. This is an absolute showstopper for me, so I intend to go back to 16.04 if I need to.

Is there any older version of qemu-system-x86_64 I can safely roll back to on Ubuntu 17.10, or is this asking for even more troubles?