Re: [PATCH v3 0/4] tdx-guest: Make Quote buffer size dynamic

[Sean Christopherson <seanjc@google.com>]

On Wed, Aug 12, 2026, Rick P Edgecombe wrote:
> On Wed, 2026-08-12 at 15:37 -0700, Peter Fang wrote:
> > > 
> > > But part of this too, is that "DICE" is an industry standard [0]. Some of
> > > the existing TDX attestation format is TDX specific, and moving to the
> > > standard is expected to make the verifier better. So TDX does not have full
> > > flexibility in choosing which bits go where. There is some. But I'm not sure
> > > which.
> > 
> > In the SGX era, a lot of this attestation stuff was Intel proprietary
> > and that caused a lot of pain. To follow the DICE standard the bits in
> > the report have specific places to go inside the quote blob. IOW the
> > DICE quote doesn't just carry the report like an attachment, and so the
> > two can't be separated (not without breaking the standard in some way).
> 
> Yea that was my suspicion. I'm not sure if separating them was really Sean's
> understanding or not. 

LOL, most definitely not.  Though I have a naive question at this point: why can't
the TDX-Module extract the bits from the report and put them in the right places
when generating the quote?

> But the other part is that the verifiers and other VMM infrastructures are
> already expecting this standard format. It would have a lot of downsides.
> 
> But the "grow the report" or "grow the report and quote" are still options that
> leave the quote in the expected DICE format, right? Sean I'll assume you still
> prefer the "grow both" option for the sake of kicking the quoting
> responsibilities out of KVM.

Not necessarily.  If doing the right thing from a "what's intended and sane"
perspective is to put some quoting responsibilities on KVM, then so be it.  But
I would like to have a passing understanding of what all is going on, if only so
that I can justify why the new uAPI is being added when I send Paolo a pull
request.  I'm pushing back purely because I quite literally don't understand why
KVM needs to be involved.