Since you cannot know what kind of changes the user will do in libvirt you cannot be sure that VDSM will be able to live with them.
By "Allowing" this officially you will create an impression that it is safe, which will cause frustration for the user if VDSM breaks.
So keeping this as "do at your own risk, we want nothing to do with it" sounds like a good plan to me :)

But ignoring that, what kind of behaviour would you like? maybe the ability to pass custom libvirt flags on VM startup?
This can be pretty easily Implemented as an all purpose hook, isn't it? (write once, pass any argument you like)

----- Original Message -----
From: "Dead Horse" <deadhorseconsulting@gmail.com>
To: "engine-devel" <engine-devel@ovirt.org>
Sent: Friday, August 2, 2013 7:43:31 PM
Subject: [Engine-devel] direct manipulation of libvirt

A broad question here, perhaps not a possibility but I figured I would toss it out there anyway.

VDSM is great at what it does, however there are those times when direct manipulation of libvirt or libvirt VM configuration would be very handy. The safe defaults and tested VM configurations that VDSM/ovirt provides are great. However at times it would be nice to simply connect to a hypervisor managed by ovirt/vdsm and make a couple changes to a VM (via virt-manager or directly via virsh).

This could be enabling a new feature that has made it's way into QEMU/libvirt/KVM or tweaking a VM configuration for whatever reason. Now there is nothing stopping someone from doing this now either directly or via VDSM hooks. Hooks are a pain along with the custom properties to jack them into engine. Direct manipulation of libvirt since it has been upstarted by vdsm results in an unhappy VDSM/engine.

Thoughts?
- DHC

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