I have a Server 2008R2 guest running inside a KVM host. I've enabled various Hyper-V enlightenments through KVM (-cpu host,hv_relaxed,hv_vapic,hv_spinlocks=0x1000), but I'm not sure how I can confirm that the guest is actually making use of them.
How can I list what enlightenments the guest is actually making use of?
I don't think you can.
Those things are always enabled when running on top of Hyper-V. So there's no reason within a Windows VM to even ask the question. The Hyper-V team didn't make a way to ask a question that would always return the same answer. I suppose you just have to trust that KVM folks exposed them in the exact same way that Hyper-V would, in which case the answer will be that the guest is making use of all of them.