No, I was looking in the wrong place - qemu-kvm.postinst already does exactly that!
In fact, I'm starting to wonder whether the way to reproduce this would be to not 'apt-get install kvm' before installing libvirt-bin. The kvm kernel module will be loaded, but won't be configured for use by libvirt. I'm not sure whether we should consider that a bug, or mis-configuration by the admin.
No, I was looking in the wrong place - qemu-kvm.postinst already does exactly that!
In fact, I'm starting to wonder whether the way to reproduce this would be to not 'apt-get install kvm' before installing libvirt-bin. The kvm kernel module will be loaded, but won't be configured for use by libvirt. I'm not sure whether we should consider that a bug, or mis-configuration by the admin.