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| -rw-r--r-- | Documentation/x86/index.rst | 1 | ||||
| -rw-r--r-- | Documentation/x86/microcode.rst (renamed from Documentation/x86/microcode.txt) | 62 |
2 files changed, 35 insertions, 28 deletions
diff --git a/Documentation/x86/index.rst b/Documentation/x86/index.rst index 6719defc16f8..ae29c026be72 100644 --- a/Documentation/x86/index.rst +++ b/Documentation/x86/index.rst @@ -22,3 +22,4 @@ x86-specific Documentation intel_mpx amd-memory-encryption pti + microcode diff --git a/Documentation/x86/microcode.txt b/Documentation/x86/microcode.rst index 79fdb4a8148a..a320d37982ed 100644 --- a/Documentation/x86/microcode.txt +++ b/Documentation/x86/microcode.rst @@ -1,7 +1,11 @@ - The Linux Microcode Loader +.. SPDX-License-Identifier: GPL-2.0 -Authors: Fenghua Yu <fenghua.yu@intel.com> - Borislav Petkov <bp@suse.de> +========================== +The Linux Microcode Loader +========================== + +:Authors: - Fenghua Yu <fenghua.yu@intel.com> + - Borislav Petkov <bp@suse.de> The kernel has a x86 microcode loading facility which is supposed to provide microcode loading methods in the OS. Potential use cases are @@ -10,8 +14,8 @@ and updating the microcode on long-running systems without rebooting. The loader supports three loading methods: -1. Early load microcode -======================= +Early load microcode +==================== The kernel can update microcode very early during boot. Loading microcode early can fix CPU issues before they are observed during @@ -26,8 +30,10 @@ loader parses the combined initrd image during boot. The microcode files in cpio name space are: -on Intel: kernel/x86/microcode/GenuineIntel.bin -on AMD : kernel/x86/microcode/AuthenticAMD.bin +on Intel: + kernel/x86/microcode/GenuineIntel.bin +on AMD : + kernel/x86/microcode/AuthenticAMD.bin During BSP (BootStrapping Processor) boot (pre-SMP), the kernel scans the microcode file in the initrd. If microcode matching the @@ -42,8 +48,8 @@ Here's a crude example how to prepare an initrd with microcode (this is normally done automatically by the distribution, when recreating the initrd, so you don't really have to do it yourself. It is documented here for future reference only). +:: ---- #!/bin/bash if [ -z "$1" ]; then @@ -76,15 +82,15 @@ here for future reference only). cat ucode.cpio $INITRD.orig > $INITRD rm -rf $TMPDIR ---- + The system needs to have the microcode packages installed into /lib/firmware or you need to fixup the paths above if yours are somewhere else and/or you've downloaded them directly from the processor vendor's site. -2. Late loading -=============== +Late loading +============ There are two legacy user space interfaces to load microcode, either through /dev/cpu/microcode or through /sys/devices/system/cpu/microcode/reload file @@ -94,9 +100,9 @@ The /dev/cpu/microcode method is deprecated because it needs a special userspace tool for that. The easier method is simply installing the microcode packages your distro -supplies and running: +supplies and running:: -# echo 1 > /sys/devices/system/cpu/microcode/reload + # echo 1 > /sys/devices/system/cpu/microcode/reload as root. @@ -104,29 +110,29 @@ The loading mechanism looks for microcode blobs in /lib/firmware/{intel-ucode,amd-ucode}. The default distro installation packages already put them there. -3. Builtin microcode -==================== +Builtin microcode +================= The loader supports also loading of a builtin microcode supplied through the regular builtin firmware method CONFIG_EXTRA_FIRMWARE. Only 64-bit is currently supported. -Here's an example: +Here's an example:: -CONFIG_EXTRA_FIRMWARE="intel-ucode/06-3a-09 amd-ucode/microcode_amd_fam15h.bin" -CONFIG_EXTRA_FIRMWARE_DIR="/lib/firmware" + 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: +This basically means, you have the following tree structure locally:: -/lib/firmware/ -|-- amd-ucode -... -| |-- microcode_amd_fam15h.bin -... -|-- intel-ucode -... -| |-- 06-3a-09 -... + /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. |