Thanks for the response. /var/run/libvirt/qemu/ seems to be exactly what
I'm looking for. It would, however, be nice to be able to access this
file without root privileges.
Use a tiny setuid C program that reads the relevant file and writes it to a known UNIX-domain socket that has more liberal permissions? On past experience, I wouldn't expect this to end up being supported in libvirt, though there's nothing to stop you creating your own patched version.
Cheers,
- Peter