As an update, I successfully rolled back my BIOS to an earlier
version. With this change, tboot works again! GETSEC[SENTER] executes
with no errors and I get into the secure state. So it is definitely
some problem relating to the new BIOS.

Interestingly, I dumped the DMAR tables created by the working BIOS
and they are byte for byte identical to what they were with the
non-working BIOS. So clearly there is no point in going over those
tables with a fine tooth comb to figure out what SINIT doesn't like
about them. Something else must be different. I'd say the SINIT error
codes are not particularly informative about what is going wrong in
this case.

I hope the SINIT team will still look into this. I can easily go back
to the newer BIOS in order to reproduce the failing state. The new
BIOS has the advantage that I can reboot after an SINIT failure and
read the errorcode register. With the old BIOS, attempts to reboot
hang in the BIOS and it's not possible to read the errorcodes, which
made debugging TXT almost impossible.

So I can either use the new BIOS which would allow some debugging but
which unfortunately doesn't work with SINIT; or I can use the old BIOS
which works with SINIT but reveals nothing when there is a failure.
Neither is a great alternative.

Hal Finney

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