Re: [PATCH V5] efi/tpm: Fix the issue where the CC platforms event log header can't be correctly identified

[James Bottomley <James.Bottomley@HansenPartnership.com>]

On Sat, 2025-07-12 at 10:55 +0800, yangge1116@126.com wrote:
> From: Ge Yang <yangge1116@126.com>
> 
> Since commit d228814b1913 ("efi/libstub: Add get_event_log() support
> for CC platforms") reuses TPM2 support code for the CC platforms,
> when launching a TDX virtual machine with coco measurement enabled,
> the following error log is generated:
> 
> [Firmware Bug]: Failed to parse event in TPM Final Events Log
> 
> Call Trace:
> efi_config_parse_tables()
>   efi_tpm_eventlog_init()
>     tpm2_calc_event_log_size()
>       __calc_tpm2_event_size()
> 
> The pcr_idx value in the Intel TDX log header is 1, causing the
> function __calc_tpm2_event_size() to fail to recognize the log
> header, ultimately leading to the "Failed to parse event in TPM Final
> Events Log" error.
> 
> According to UEFI Specification 2.10, Section 38.4.1: For TDX, TPM
> PCR 0 maps to MRTD, so the log header uses TPM PCR 1 instead.

This isn't a justification ... Intel just screwed up.  Whatever the
UEFI spec says about PCR mapping, the log spec the TCG produces
requires the header event to have a pcrIndex of 0 and, since it isn't
recorded in a PCR, it doesn't matter what the mapping is.

Just say Intel misread the spec and wrongly sets pcrIndex to 1 in the
header and since they did this, we fear others might, so we're relaxing
the header check.

Regards,

James