Re: [RFC 05/33] KVM: x86: hyper-v: Introduce VTL call/return prologues in hypercall page

[Sean Christopherson]

On Fri, Dec 01, 2023, Nicolas Saenz Julienne wrote:
> > To support this I think that we can add a userspace msr filter on the HV_X64_MSR_HYPERCALL,
> > although I am not 100% sure if a userspace msr filter overrides the in-kernel msr handling.
> 
> I thought about it at the time. It's not that simple though, we should
> still let KVM set the hypercall bytecode, and other quirks like the Xen
> one.

Yeah, that Xen quirk is quite the killer.

Can you provide pseudo-assembly for what the final page is supposed to look like?
I'm struggling mightily to understand what this is actually trying to do.