[SeaBIOS] Re: Seabios Xen TPM check

[Stefan Berger]

On 6/11/20 8:36 AM, Jason Andryuk wrote:
> Hi,
>
> SeaBIOS commit 67643955c746 (make SeaBios compatible with Xen vTPM.)
> made tpm_start() exit before calling tpm_startup().  The commit
> message has no explanation why this change was made.  Does anyone
> remember why it was made?
>
> The code today means SeaBIOS will not populate PCRs when running on
> Xen.  If I revert the patch, SeaBIOS populates PCRs as one would
> expect.  This is with a QEMU-emulated TPM backed by swtpm in TPM 1.2
> mode (qemu & swtpm running in a linux stubdom).
>
> Any insight is appreciated.

My guess would be that for some reason the TPM 1.2 was already started 
up through other means and didn't need the SeaBIOS tpm_startup() to run.
> Thanks,
> Jason