I did some more testing and everything looks good to me. I've
addressed your previous comments as well (see below). I wasn't sure if
I needed to squash the commits so I just included all three patches. I
did reorder them to place your wrap patch before mine since the
libvirt service depends on that change.

>> +(define libvirt-service-type
>> +  (service-type (name 'libvirt)
>> +             (extensions
>> +                 (list
>> +                  (service-extension polkit-service-type (compose list libvirt-configuration-libvirt))
>
> Line length could be better here, just by putting the (compose ... )
> bit on the line after the polkit-service-type.
>

Agreed. This is fixed in the attached patch.

>> +                  (service-extension profile-service-type
>> +                                     (compose list
>> +                                           (lambda (package) qemu)
>> +                                     libvirt-configuration-libvirt))
>
> This confused me for a bit, until I realised that a simpler way of
> expressing this would be (const (list qemu)) if I'm correct? Also, it
> would be good to explain why this needs to happen in a comment.
>

That didn't work. qemu doesn't need to be installed in the system
profile anyway so I've removed this.

>> +(define virtlog-service-type
>> +  (service-type (name 'virtlogd)
>> +             (extensions
>> +                 (list
>> +                  (service-extension profile-service-type
>> +                                     (compose list
>> +
>> virtlog-configuration-libvirt))
>
> What function does this extension have? As far as I understood from the
> documentation you wrote, this is used from the libvirt service.

Now that I have a better understanding of how this works I realize
this was unnecessary and it's been removed too.