Comment 4 for bug 1755153

The steps to reproduce in the bug description say 'install 18.04' and the uname command prints a 4.13.0-32 kernel.

Since I assume that your setup is an 18.04 host with an 18.04 guest, the kernel (or better the Ubuntu 18.04 daily build) in use is _very_ outdated.
Current 18.04 kernels are 4.15:
 linux-generic | 4.15.0.10.11 | bionic | ppc64el
 linux-generic | 4.15.0.12.13 | bionic-proposed | ppc64el
Even libvirt (libvirt-bin 4.0.0-1ubuntu2) seems to be quite old - current is:
 libvirt-bin | 4.0.0-1ubuntu4 | bionic | ppc64el

Please always update your system to the very latest level before testing, especially on releases that are currently in development - like 18.04 today - that potentially get updated packages virtually every day. So please re-try on latest packages.