[suggestion] ME disablement via removing VSCC values

[skochinsky]

VSCC table is present in the descriptor region and tells the ME (and PCH?) about Vendor Specific Component Capabilities of the flash chips supported by the system.

A birdie told me that a missing VSCC value will place the ME into recovery mode since it won't be able to write to flash without knowing if the connected part is supported.

It seems the table is located at VTBA (whose value and size are encoded in the FLUMAP1).

Clearing this table may be another "soft disable" option in addition to AltMeDisable.

[platomav]

Also SMBus can be found at the FD. Various other settings too if someone wants to go the extra mile. I verified VSCC & SMBus removal here (ME 6, Ibex Peak PCH). If tampered with, it should result in a "VSCC_FAILURE" error at PhaseStatus of FWStatusRegister1 as seen here.

[raz123]

Good catch. More info:

VSCC Table
This section is used to store information to setup flash access for ME. This does not
have any effect on the usage of the Flash programming Tool (FPT). If the
information in this section is incorrect, the Intel® ME Firmware may not
communicate with the flash device. This information provided is dependent on the
flash device used on the system. More detail please refer to PCH SPI programming
guide Section 6.4

Source: System Tools User Guide for
Intel® Management Engine
Firmware 6.0 (Corporate) -- http://composter.com.ua/documents/System_Tools_User_Guide_for_Intel_Management_Engine.pdf

[corna]

@skochinsky Doesn't it also affect the normal operation of the BIOS?

[skochinsky]

@skochinsky Doesn't it also affect the normal operation of the BIOS?

AFAIK BIOS has its own tables for talking to flash so it should continue working.