6fcc46d1a4
Some platforms which have large amounts of RAM and also write-combining regions may decide to drop the WC regions in favor of the default when preserving MTRRs for the OS. From a data safety perspective, this is safe to do, but if, say, the graphics framebuffer is the region that is changed from WC to UC/WB, then the performance of writing to the framebuffer will decrease dramatically. Modern OSes typically use Page Attribute Tables (PAT) to determine the cacheability on a page level and usually do not touch the MTRRs. Thus, it is believed to be safe to stop reserving MTRRs for the OS, in general; PentiumII is the exception here in that OSes that still support that may still require MTRRs to be available. In any case, if the OS wants to reprogram all of the MTRRs, it is of course still free to do so (after consulting the e820 table). BUG=b:185452338 TEST=Verify MTRR programming on a brya (where `sa_add_dram_resources` was faked to think it had 32 GiB of DRAM installed) and variable MTRR map includes a WC entry for the framebuffer (and all the RAM): MTRR: default type WB/UC MTRR counts: 13/9. MTRR: UC selected as default type. MTRR: 0 base 0x0000000000000000 mask 0x00003fff80000000 type 6 MTRR: 1 base 0x0000000077000000 mask 0x00003fffff000000 type 0 MTRR: 2 base 0x0000000078000000 mask 0x00003ffff8000000 type 0 MTRR: 3 base 0x0000000090000000 mask 0x00003ffff0000000 type 1 MTRR: 4 base 0x0000000100000000 mask 0x00003fff00000000 type 6 MTRR: 5 base 0x0000000200000000 mask 0x00003ffe00000000 type 6 MTRR: 6 base 0x0000000400000000 mask 0x00003ffc00000000 type 6 MTRR: 7 base 0x0000000800000000 mask 0x00003fff80000000 type 6 MTRR: 8 base 0x000000087fc00000 mask 0x00003fffffc00000 type 0 ADL has 9 variable-range MTRRs, previously 8 of them were used, and there was no separate entry for the framebuffer, thus leaving the default MTRR in place of uncached. Change-Id: I2ae2851248c95fd516627b101ebcb36ec59c29c3 Signed-off-by: Tim Wawrzynczak <twawrzynczak@chromium.org> Reviewed-on: https://review.coreboot.org/c/coreboot/+/52522 Tested-by: build bot (Jenkins) <no-reply@coreboot.org> Reviewed-by: Angel Pons <th3fanbus@gmail.com> Reviewed-by: Furquan Shaikh <furquan@google.com> |
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| 3rdparty | ||
| Documentation | ||
| LICENSES | ||
| configs | ||
| payloads | ||
| src | ||
| tests | ||
| util | ||
| .checkpatch.conf | ||
| .clang-format | ||
| .editorconfig | ||
| .gitignore | ||
| .gitmodules | ||
| .gitreview | ||
| AUTHORS | ||
| COPYING | ||
| MAINTAINERS | ||
| Makefile | ||
| Makefile.inc | ||
| README.md | ||
| gnat.adc | ||
| toolchain.inc | ||
README.md
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 https://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:
Build Requirements
- make
- gcc / g++
Because Linux distribution compilers tend to use lots of patches. coreboot
does lots of "unusual" things in its build system, some of which break due
to those patches, sometimes by gcc aborting, sometimes - and that's worse -
by generating broken object code.
Two options: use our toolchain (eg. make crosstools-i386) or enable the
ANY_TOOLCHAINKconfig option if you're feeling lucky (no support in this case). - iasl (for targets with ACPI support)
- pkg-config
- libssl-dev (openssl)
Optional:
- doxygen (for generating/viewing documentation)
- gdb (for better debugging facilities on some targets)
- ncurses (for
make menuconfigandmake nconfig) - flex and bison (for regenerating parsers)
Building coreboot
Please consult https://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 https://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:
You can contact us directly on the coreboot mailing list:
https://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.