| commit | 833e9bad4762e0dca6c867d3a18dbaf6d5166be8 | [log] [tgz] |
|---|---|---|
| author | Evgeny Zinoviev <me@ch1p.io> | Thu Nov 21 21:47:31 2019 +0300 |
| committer | Angel Pons <th3fanbus@gmail.com> | Sun Feb 07 23:06:52 2021 +0000 |
| tree | 3e5ad211109146671cfd1efae96e64989d901727 | |
| parent | 20a609f0f77ef84ef7f4f5e487000347c361a29e [diff] |
sb/intel/bd82x6x: Support ME Soft Temporary Disable Mode
- Add support for ME Soft Temporary Disable Mode. In this mode, ME
doesn't load its kernel and freezes at Bring UP (BUP) phase. This mode
is saved in ME NVRAM (and thus will remain for next reboots and
poweroffs).
- Add support of new CMOS option for Sandy Bridge and Ivy Bridge
ThinkPads.
HOW TO USE
To disable ME:
1. nvramtool -w me_state=Disabled
2. reboot
To enable it back:
1. nvramtool -w me_state=Normal
2. reboot
To check current status:
intelmetool -m
Tested on ThinkPad X230 and ThinkPad X220.
BACKGROUND
There's no Intel documentation that would explain how this should be
implemented, in public. Working binary sequence for MKHI command to put
ME in Soft Temporary Disable Mode, as well as a way to bring ME out of
it (by writing to H_GS register), was found and published by researchers
from PT Security:
1. To disable ME, BIOS issues the disable command (before End of Post)
and reboots. ME is supposed to be disabled on the next boot after
DID (DRAM Init Done).
My numerous tests show that issuing the command and rebooting is not
enough. If we reboot too early, ME will not be disabled. Apparently,
it is doing something in background after receiving the command. It
works with a delay of 500-1000 ms.
I also tried to dump all known (documented) registers, such as GMES
and HFS, before and during the next 2 seconds after execution of the
disable command to find a possible indication that something's
changed in ME and we're ready to reboot. Found nothing
unfortunately.
2. To enable ME back, host writes value 0x20000000 to H_GS.
PT slides don't contain any more information on it, but my tests
show, that after writing this value, GMES[31:28] is changing from
0x01 (BUP phase) to 0x03 (Policy Module) to 0x06 (Host
Communication). Then, after some more time, fw_init_complete bit of
HFS becomes 1.
This means that ME starts loading its kernel immediately, without
reboot.
On the other hand, Lenovo BIOS clearly perform a reboot after
enabling it (one reboot after saving the settings, then ThinkPad
logo appears, and then one more reboot). I'm assuming we have to
reset too.
Change-Id: Ic01526c9731cbef4e8552bbc352133a2415787c2
Signed-off-by: Evgeny Zinoviev <me@ch1p.io>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/37115
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-by: Nico Huber <nico.h@gmx.de>
coreboot is a Free Software project aimed at replacing the proprietary BIOS (firmware) found in most computers. coreboot performs a little bit of hardware initialization and then executes additional boot logic, called a payload.
With the separation of hardware initialization and later boot logic, coreboot can scale from specialized applications that run directly firmware, run operating systems in flash, load custom bootloaders, or implement firmware standards, like PC BIOS services or UEFI. This allows for systems to only include the features necessary in the target application, reducing the amount of code and flash space required.
coreboot was formerly known as LinuxBIOS.
After the basic initialization of the hardware has been performed, any desired "payload" can be started by coreboot.
See https://www.coreboot.org/Payloads for a list of supported payloads.
coreboot supports a wide range of chipsets, devices, and mainboards.
For details please consult:
ANY_TOOLCHAIN Kconfig option if you're feeling lucky (no support in this case).Optional:
make menuconfig and make nconfig)Please consult https://www.coreboot.org/Build_HOWTO for details.
If you want to test coreboot without any risks before you really decide to use it on your hardware, you can use the QEMU system emulator to run coreboot virtually in QEMU.
Please see https://www.coreboot.org/QEMU for details.
Further details on the project, a FAQ, many HOWTOs, news, development guidelines and more can be found on the coreboot website:
You can contact us directly on the coreboot mailing list:
https://www.coreboot.org/Mailinglist
The copyright on coreboot is owned by quite a large number of individual developers and companies. Please check the individual source files for details.
coreboot is licensed under the terms of the GNU General Public License (GPL). Some files are licensed under the "GPL (version 2, or any later version)", and some files are licensed under the "GPL, version 2". For some parts, which were derived from other projects, other (GPL-compatible) licenses may apply. Please check the individual source files for details.
This makes the resulting coreboot images licensed under the GPL, version 2.