projects / linux-2.6-block.git / blame
| Commit | Line | Data |
|---|---|---|
| 0d91ea86 FY |
1 | Early load microcode |
| 2 | ==================== | |
| 3 | By Fenghua Yu <fenghua.yu@intel.com> | |
| 4 | ||
| 5 | Kernel can update microcode in early phase of boot time. Loading microcode early | |
| 6 | can fix CPU issues before they are observed during kernel boot time. | |
| 7 | ||
| 8 | Microcode is stored in an initrd file. The microcode is read from the initrd | |
| 9 | file and loaded to CPUs during boot time. | |
| 10 | ||
| 11 | The format of the combined initrd image is microcode in cpio format followed by | |
| 12 | the initrd image (maybe compressed). Kernel parses the combined initrd image | |
| 13 | during boot time. The microcode file in cpio name space is: | |
| 757885e9 JS |
14 | on Intel: kernel/x86/microcode/GenuineIntel.bin |
| 15 | on AMD : kernel/x86/microcode/AuthenticAMD.bin | |
| 0d91ea86 FY |
16 | |
| 17 | During BSP boot (before SMP starts), if the kernel finds the microcode file in | |
| 18 | the initrd file, it parses the microcode and saves matching microcode in memory. | |
| 19 | If matching microcode is found, it will be uploaded in BSP and later on in all | |
| 20 | APs. | |
| 21 | ||
| 22 | The cached microcode patch is applied when CPUs resume from a sleep state. | |
| 23 | ||
| 24 | There are two legacy user space interfaces to load microcode, either through | |
| 25 | /dev/cpu/microcode or through /sys/devices/system/cpu/microcode/reload file | |
| 26 | in sysfs. | |
| 27 | ||
| 28 | In addition to these two legacy methods, the early loading method described | |
| 29 | here is the third method with which microcode can be uploaded to a system's | |
| 30 | CPUs. | |
| 31 | ||
| 32 | The following example script shows how to generate a new combined initrd file in | |
| 33 | /boot/initrd-3.5.0.ucode.img with original microcode microcode.bin and | |
| 34 | original initrd image /boot/initrd-3.5.0.img. | |
| 35 | ||
| 36 | mkdir initrd | |
| 37 | cd initrd | |
| 757885e9 JS |
38 | mkdir -p kernel/x86/microcode |
| 39 | cp ../microcode.bin kernel/x86/microcode/GenuineIntel.bin (or AuthenticAMD.bin) | |
| 40 | find . | cpio -o -H newc >../ucode.cpio | |
| 0d91ea86 FY |
41 | cd .. |
| 42 | cat ucode.cpio /boot/initrd-3.5.0.img >/boot/initrd-3.5.0.ucode.img | |
| b5843032 BP |
43 | |
| 44 | Builtin microcode | |
| 45 | ================= | |
| 46 | ||
| 47 | We can also load builtin microcode supplied through the regular firmware | |
| 48 | builtin method CONFIG_FIRMWARE_IN_KERNEL. Here's an example: | |
| 49 | ||
| 50 | CONFIG_FIRMWARE_IN_KERNEL=y | |
| 51 | CONFIG_EXTRA_FIRMWARE="intel-ucode/06-3a-09 amd-ucode/microcode_amd_fam15h.bin" | |
| 52 | CONFIG_EXTRA_FIRMWARE_DIR="/lib/firmware" | |
| 53 | ||
| 54 | This basically means, you have the following tree structure locally: | |
| 55 | ||
| 56 | /lib/firmware/ | |
| 57 | |-- amd-ucode | |
| 58 | ... | |
| 59 | | |-- microcode_amd_fam15h.bin | |
| 60 | ... | |
| 61 | |-- intel-ucode | |
| 62 | ... | |
| 63 | | |-- 06-3a-09 | |
| 64 | ... | |
| 65 | ||
| 66 | so that the build system can find those files and integrate them into | |
| 67 | the final kernel image. The early loader finds them and applies them. |