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-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.