Re: [PATCH RFC 00/20] attestation: Add a common subsystem and TDX support

[Jason Gunthorpe]

On Sat, Oct 17, 2026 at 10:06:04PM +0300, Jarkko Sakkinen wrote:
> On Sat, Oct 17, 2026 at 11:16:07AM -0700, Dionna Glaze wrote:
> > +Jarkko
> > The TPM driver is pretty entrenched and heavily used by different user
> > space applications, so it seems really ambitious to bundle in TPM
> > here.
> 
> This is something on the table thanks to Trenchboot and its early boot
> code.

I've proposed that there be no early TPM in the Linux DRTM
implementation. The trampoline would just do a bit of additional work
with its existing TPM code before it reaches Linux.

https://lore.kernel.org/all/20261016165135.GA494690@xxxxxxxxxx/

My intention with attestation subsystem: tpm and DRTM is to follow the
ARM design and get ACPI up enough to reach a HW driver. Attestation
subsystem will multiplex the DRTM "PCR" logging to which ever ROT that
DRTM launch selected. This is another reason why I dont like early TPM
because it turns from just early TPM, already hard, into
early-every-ROT which is much worse.

I view all the stuff you are listing to make tpm early work as too
difficult compared to just having the trampoline do it since it
already must have a TPM extend operation inside it.

Jason