projects / GitHub / mt8127 / android_kernel_alcatel_ttab.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: | |
| 14 | kernel/x86/microcode/GenuineIntel.bin | |
| 15 | ||
| 16 | During BSP boot (before SMP starts), if the kernel finds the microcode file in | |
| 17 | the initrd file, it parses the microcode and saves matching microcode in memory. | |
| 18 | If matching microcode is found, it will be uploaded in BSP and later on in all | |
| 19 | APs. | |
| 20 | ||
| 21 | The cached microcode patch is applied when CPUs resume from a sleep state. | |
| 22 | ||
| 23 | There are two legacy user space interfaces to load microcode, either through | |
| 24 | /dev/cpu/microcode or through /sys/devices/system/cpu/microcode/reload file | |
| 25 | in sysfs. | |
| 26 | ||
| 27 | In addition to these two legacy methods, the early loading method described | |
| 28 | here is the third method with which microcode can be uploaded to a system's | |
| 29 | CPUs. | |
| 30 | ||
| 31 | The following example script shows how to generate a new combined initrd file in | |
| 32 | /boot/initrd-3.5.0.ucode.img with original microcode microcode.bin and | |
| 33 | original initrd image /boot/initrd-3.5.0.img. | |
| 34 | ||
| 35 | mkdir initrd | |
| 36 | cd initrd | |
| 37 | mkdir kernel | |
| 38 | mkdir kernel/x86 | |
| 39 | mkdir kernel/x86/microcode | |
| 40 | cp ../microcode.bin kernel/x86/microcode/GenuineIntel.bin | |
| 41 | find .|cpio -oc >../ucode.cpio | |
| 42 | cd .. | |
| 43 | cat ucode.cpio /boot/initrd-3.5.0.img >/boot/initrd-3.5.0.ucode.img |