Re: [PATCH v2 16/17] KVM: TDX: Add in-kernel Quote generation

[Edgecombe, Rick P]

On Wed, 2026-07-08 at 15:28 -0700, Sean Christopherson wrote:
> > I'll just add that this design decision comes from the fact that we're
> > looking at different kinds of future attestation stuff. Some of it is
> > quite complex (like post-quantum crypto). Some of it may even require
> > more complicated interactions with the S3M. Hiding these details allows
> > all this crypto stuff to look like just another TDX module release.
> 
> IMO, that's not a good thing.  Burying more code and more complexity in what
> is supposed to be a minimal TCB doesn't seem like a "win".  I can certainly
> appreciate that interacting with the S3M microcontroller isn't something we
> want in KVM, but that's why drivers/ exists.

This is an interesting take and makes me think even more that we need to be
socializing the TDX arch stuff a lot more.

> 
> > The host kernel shouldn't be burdened with attestation intricacies, 
> 
> Oh, but the kernel has to be, at least to the point where the kernel has
> enough information to guarantee backwards compatibility, enumerate choices,
> etc.  If you're saying that the TDX module will always generate reports that
> are compatible across TDX Module updates, then we probably don't have anything
> to worry about, but it seems unlikely everything can Just Work while also
> updating the core crypto algorithms and whatnot.

There are absolutely some ABI sensitivity here that need to be considered, and
unfortunately the analysis from the internal debates did not make into the
public presentation of the feature. In fact the whole DICE part of this series
is missing a lot of needed context.

I think I mentioned that we want to come to talk about migration in PUCK, it
might help to bring this one in too. Despite being small, it actually took quite
a bit for us to wrap our heads around it. Would you want to try that? Or we
could fill out the logs and coverletter in v3. Or we could just try to slowly
walk through it all here. I was thinking a call may shorten the loops.