mirror of
https://github.com/torvalds/linux.git
synced 2024-11-23 04:31:50 +00:00
9f3cc2a077
Document that builtin microcode is 64-bit only. Also, improve/add comments to places. Signed-off-by: Borislav Petkov <bp@suse.de> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Borislav Petkov <bp@alien8.de> Cc: Brian Gerst <brgerst@gmail.com> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: linux-doc@vger.kernel.org Link: http://lkml.kernel.org/r/1465225850-7352-10-git-send-email-bp@alien8.de Signed-off-by: Ingo Molnar <mingo@kernel.org>
71 lines
2.4 KiB
Plaintext
71 lines
2.4 KiB
Plaintext
Early load microcode
|
|
====================
|
|
By Fenghua Yu <fenghua.yu@intel.com>
|
|
|
|
Kernel can update microcode in early phase of boot time. Loading microcode early
|
|
can fix CPU issues before they are observed during kernel boot time.
|
|
|
|
Microcode is stored in an initrd file. The microcode is read from the initrd
|
|
file and loaded to CPUs during boot time.
|
|
|
|
The format of the combined initrd image is microcode in cpio format followed by
|
|
the initrd image (maybe compressed). Kernel parses the combined initrd image
|
|
during boot time. The microcode file in cpio name space is:
|
|
on Intel: kernel/x86/microcode/GenuineIntel.bin
|
|
on AMD : kernel/x86/microcode/AuthenticAMD.bin
|
|
|
|
During BSP boot (before SMP starts), if the kernel finds the microcode file in
|
|
the initrd file, it parses the microcode and saves matching microcode in memory.
|
|
If matching microcode is found, it will be uploaded in BSP and later on in all
|
|
APs.
|
|
|
|
The cached microcode patch is applied when CPUs resume from a sleep state.
|
|
|
|
There are two legacy user space interfaces to load microcode, either through
|
|
/dev/cpu/microcode or through /sys/devices/system/cpu/microcode/reload file
|
|
in sysfs.
|
|
|
|
In addition to these two legacy methods, the early loading method described
|
|
here is the third method with which microcode can be uploaded to a system's
|
|
CPUs.
|
|
|
|
The following example script shows how to generate a new combined initrd file in
|
|
/boot/initrd-3.5.0.ucode.img with original microcode microcode.bin and
|
|
original initrd image /boot/initrd-3.5.0.img.
|
|
|
|
mkdir initrd
|
|
cd initrd
|
|
mkdir -p kernel/x86/microcode
|
|
cp ../microcode.bin kernel/x86/microcode/GenuineIntel.bin (or AuthenticAMD.bin)
|
|
find . | cpio -o -H newc >../ucode.cpio
|
|
cd ..
|
|
cat ucode.cpio /boot/initrd-3.5.0.img >/boot/initrd-3.5.0.ucode.img
|
|
|
|
Builtin microcode
|
|
=================
|
|
|
|
We can also load builtin microcode supplied through the regular firmware
|
|
builtin method CONFIG_FIRMWARE_IN_KERNEL. Only 64-bit is currently
|
|
supported.
|
|
|
|
Here's an example:
|
|
|
|
CONFIG_FIRMWARE_IN_KERNEL=y
|
|
CONFIG_EXTRA_FIRMWARE="intel-ucode/06-3a-09 amd-ucode/microcode_amd_fam15h.bin"
|
|
CONFIG_EXTRA_FIRMWARE_DIR="/lib/firmware"
|
|
|
|
This basically means, you have the following tree structure locally:
|
|
|
|
/lib/firmware/
|
|
|-- amd-ucode
|
|
...
|
|
| |-- microcode_amd_fam15h.bin
|
|
...
|
|
|-- intel-ucode
|
|
...
|
|
| |-- 06-3a-09
|
|
...
|
|
|
|
so that the build system can find those files and integrate them into
|
|
the final kernel image. The early loader finds them and applies them.
|