Re: [PATCH] KVM: TDX: Fix APIC MSR ranges in tdx_has_emulated_msr()

Edgecombe, Rick P
2026-04-03T19:30:17Z

On Fri, 2026-04-03 at 12:07 -0700, Sean Christopherson wrote:
> > > No?  Don't we just want to allow access to MSRs that aren't accelerated?
> > > What the TDX-Module supports is largely irrelevant, I think.
> >
> > Not sure if I might be missing the point here. As above, we don't have
> > enough info to know which MSRs are accelerated. If the guest enabled #VE
> > reduction, it changes which ones are accelerated and the VMM is not
> > notified.
>
> What does the "accleration" in that case?  Or does it reduce which ones are
> accelerated?

I mean ones where wrmsr is handled by the TDX module instead of generating a #VE
that gets morphed into TDVMCALL by the guest. Actually usually called "native",
but I just reused your "accelerated" term from the mail.

So... "Reduced #VE" (also called "VE reduction") reduces which things cause a
#VE. The guest opts into it and the TDX module starts behaving differently. It's
kind of grab bag of changes including changing CPUID behavior, which is another
wrinkle. It was intended to fixup guest side TDX arch issues.