Re: [RFC PATCH 4/4] KVM: TDX: Check KVM exit on KVM_HC_MAP_GPA_RANGE when TD finalize

[Edgecombe, Rick P]

On Wed, 2025-06-11 at 22:01 +0800, Xiaoyao Li wrote:
> > > So, when the TDX guest calls MapGPA and KVM finds userspace doesn't opt-in
> > > KVM_HC_MAP_GPA_RANGE, just return error to userspace?
> > 
> > Why can't KVM just do what it already does, and return an error to the
> > guest?
> 
> Because GHCI requires it must be supported. No matter with the old GHCI 
> that only allows <GetTdVmCallInfo> to succeed and the success of 
> <GetTdVmCallInfo> means all the TDVMCALL leafs are support, or the 
> proposed updated GHCI that defines <MapGpa> as one of the base API/leaf, 
> and the base API must be supported by VMM.
> 
> Binbin wants to honor it.

But KVM doesn't need to support all ways that userspace could meet the GHCI
spec. If userspace opts-in to the exit, they will meet the spec. If they
configure KVM differently then they wont, but this is their decision.