Granular SCRTM Error Record (Type 0x2E) Rules

Granular SCRTM Error Record allows OEMs enabling CBnT to do “best effort” to measure the KM, BPM, IBB and policy data into PCR0 in the case of an integrity error. This record is only valid for BTGP0 / TXT enabled, as integrity errors will result in BTG enforcement. This record is optional; default behavior for integrity errors results in CBnT ACMs not starting the TPM.

ACM will verify the contents of this record only when an integrity error is found. If this record cannot be verified, ACM will fall back to default PCR0 handling (not starting the TPM at all).

1. There can be zero or one Granular SCRTM Error Records in the FIT. Additional type 0x2E entries will be ignored by the ACM.
2. The address field points to the Backup IBB address. This address must be 16b aligned, and within accessible range for ACM. Current allowed ranges are (4GB-16MB) to (4GB – 1).
3. The size field indicates the size of the Backup IBB address. This size field must be within reasonable values. Current allowed ranges as (4KB-16MB).
4. Address + size must be under (4GB –1) and above (4GB – 16MB).
5. The Version field should be set to 0x0100.
6. The C_​V bit in this entry should be clear.