47b3fb403d
Fixes spurious SMI crashes i've seen, and ACPI/SMM interaction.
For reference, the mail i've sent to ML with the bugreport:
whenever i've docked/undocked the thinkpad from the docking station,
i had to do that twice to get the action actually to happen.
First i thought that would be some error in the ACPI code. Here's a
short explanation how docking/undocking works:
1) ACPI EC Event 0x37 Handler is executed (EC sends event 0x37 on dock)
2) _Q37 does a Trap(SMI_DOCK_CONNECT). Trap is declared as follows:
a) Store(Arg0, SMIF) // SMIF is in the GNVS Memory Range
b) Store(0, 0x808) // Generates I/O Trap to SMM
c) // SMM is executed
d) Return (SMIF) // Return Result in SMIF
I've verified that a) is really executed with ACPI debugging in the
Linux Kernel. It writes the correct value to GNVS Memory. After that,
i've logged the SMIF value in SMM, which contains some random (or
former) value of SMIF.
So i've added the GNVS area to /proc/mtrr which made things work.
I've also tried a wbinvd() in SMM code, with the same result.
After reading the src/cpu/x86/smm/smmhandler.S code, i've recognized
that it starts with:
movw $(smm_gdtptr16 - smm_handler_start +
SMM_HANDLER_OFFSET), %bx
data32 lgdt %cs:(%bx)
movl %cr0, %eax
andl $0x7FFAFFD1, %eax /* PG,AM,WP,NE,TS,EM,MP = 0 */
orl $0x60000001, %eax /* CD, NW, PE = 1 */
movl %eax, %cr0
/* Enable protected mode */
data32 ljmp $0x08, $1f
...which disables caching in SMM code, but doesn't flush the cache.
So the problem is:
- the linux axpi write to the SMIF GNVS Area will be written to Cache,
because GNVS is WB
- the SMM code runs with cache disabled, and fetches SMIF directly from
Memory, which is some other value
Possible Solutions:
- enable cache in SMM (yeah, cache poisoning...)
- flush caches in SMM (really expensive)
- mark GNVS as UC in Memory Map (will only work if OS
really marks that Area as UC. Checked various vendor BIOSes, none
of them are marking NVS as UC. So this seems rather uncommon.)
- flush only the cache line which contains GNVS. Would fix this
particular problem, but users/developers could see other Bugs like
this. And not everyone likes to debug such problems. So i won't like
this solution.
Change-Id: Ie60bf91c5fd1491bc3452d5d9b7fc8eae39fd77a
Signed-off-by: Sven Schnelle <svens@stackframe.org>
Reviewed-on: http://review.coreboot.org/39
Tested-by: build bot (Jenkins)
------------------------------------------------------------------------------- coreboot README ------------------------------------------------------------------------------- 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. Payloads -------- After the basic initialization of the hardware has been performed, any desired "payload" can be started by coreboot. See http://www.coreboot.org/Payloads for a list of supported payloads. Supported Hardware ------------------ coreboot supports a wide range of chipsets, devices, and mainboards. For details please consult: * http://www.coreboot.org/Supported_Motherboards * http://www.coreboot.org/Supported_Chipsets_and_Devices Build Requirements ------------------ * gcc / g++ * make Optional: * doxygen (for generating/viewing documentation) * iasl (for targets with ACPI support) * gdb (for better debugging facilities on some targets) * ncurses (for 'make menuconfig') * flex and bison (for regenerating parsers) Building coreboot ----------------- Please consult http://www.coreboot.org/Build_HOWTO for details. Testing coreboot Without Modifying Your Hardware ------------------------------------------------ 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 http://www.coreboot.org/QEMU for details. Website and Mailing List ------------------------ Further details on the project, a FAQ, many HOWTOs, news, development guidelines and more can be found on the coreboot website: http://www.coreboot.org You can contact us directly on the coreboot mailing list: http://www.coreboot.org/Mailinglist Copyright and License --------------------- 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.