Re: [PATCH v3 3/4] KVM: TDX: Don't assume exit_reason[31:16] as all-0 in tdx_to_vmx_exit_reason()

[Sean Christopherson <seanjc@google.com>]

On Wed, Aug 12, 2026, Rick P Edgecombe wrote:
> Side note. I really dislike how tangled this area is for something that seems
> like it should be much more straightforward. Deriving partially I think from the
> overloading of the TDVMCALL leafs with the exit reasons. So we have things like:
> ...
> 	case EXIT_REASON_EPT_VIOLATION:
> 		return EXIT_REASON_EPT_MISCONFIG;
> ...

I peeked at that code again, and FWIW I still think swizzling the exit_reason for
TDVMCALL is the least awful solution.  If we don't do that, then we'll have to
update every single use of the exit_reason to demux TDVMCALL into the "real" exit
reason, which will be a mess.

And once we track the exit_reason separately from vp_enter_ret, IMO it all becomes
more logical and easier to follow.  vp_enter_ret holds the information about why
VP.ENTER returned/exited, while exit_reason holds information about why the _guest_
exited.  Obviously it's imperfect since we're still fudging EXIT_REASON_EPT_MISCONFIG,
but again, I think that's a better alternative than demuxing exit_reason in multiple
locations.