AMD microcode

This article describes updating the microcode for AMD processors.

Note
For AMD GPU firmware see the corresponding GPU driver article instead.

Installation

Emerge

Microcode updates for AMD processors are provided by sys-kernel/linux-firmware package. Install the package via:

root #emerge --ask sys-kernel/linux-firmware

Kernel

In order to load the CPU microcode the following kernel options should be enabled:

KERNEL Generic AMD microcode support enablement

Processor type and features  --->
    [*] CPU microcode loading support
    [ ]   Intel microcode patch loading support
    [*]   AMD microcode patch loading support

Warning
Modules do not work for early microcode, so make sure microcode loading is built-in not a module.

Configuration

There are multiple ways how to update the microcode.

Built-in firmware

This way the firmware files will be built directly into the kernel.

Firmware blob files selection

You can either include all the available AMD firmware files to the kernel or select just the one specific for your CPU.

All firmware files

This setup simply builds all the firmware blobs into the kernel. This can be achieved by the following kernel optionsː

KERNEL All AMD firmware blobs

Device Drivers  --->
    Generic Driver Options 
        (amd-ucode/microcode_amd.bin amd-ucode/microcode_amd_fam15h.bin amd-ucode/microcode_amd_fam16h.bin amd-ucode/microcode_amd_fam17h.bin amd/amd_sev_fam17h_model0xh.sbin) External firmware blobs to build into the kernel binary
        (/lib/firmware) Firmware blobs root directory

Warning
Every option must be set as built into the kernel, not as a kernel module.

Note
The CONFIG_EXTRA_FIRMWARE option allows specifying multiple firmware files by listing them space-separated.

Specific firmware only

This way you only include the firmware suitable to your current CPU family. The CPU family identification can be obtained from /proc/cpuinfo:

user $grep -F -m 1 "cpu family" /proc/cpuinfo

cpu family      : 22

In this example the CPU belongs to the AMD CPU family 22.

Important
The CPU family identificator listed in /proc/cpuinfo uses the decimal numeral system.

Note
Note that after the K8 AMD has started to refer to the various microarchitectures as "AMD Family xxh", where "xxh" is the hexadecimal CPU family value from the CPUID. For example, AMD Family 10h really is the official AMD name for the K10 microarchitecture. Following this convention AMD is even using AMD Family 0Fh for the previous K8 microarchitecture (CPUID 0F hexadecimal or 15 decimal).

The following table helps to identify the right firmware blob file for given CPU family identificator:

Firmware blob file	Decimal	Hexadecimal	Family name	Year	Examples
amd-ucode/microcode_amd.bin	16	10h	K10	2007	Phenom, Phenom II, Athlon II
	17	11h	Turion	2008	Athlon X2, Sempron X2, Turion X2
	18	12h	Llano, Fusion	2009	A- and E2-Series APU with Radeon HD graphics, Athlon II, Sempron X2
	20	14h	Bobcat	2011	C- and E-Series APU with Radeon HD graphics
amd-ucode/microcode_amd_fam15h.bin	21	15h	Bulldozer, Piledriver, Steamroller, Excavator	2011	FX series, A-Series APU with Radeon HD graphics, Opteron 6200/6300
amd-ucode/microcode_amd_fam16h.bin	22	16h	Jaguar, Puma	2013	A-series and E-Series APU with Radeon HD graphics
amd-ucode/microcode_amd_fam17h.bin amd/amd_sev_fam17h_model0xh.sbin	23	17h	Zen	2017	Ryzen 3|5|7, Threadripper, EPYC AMD SEV (Secure Encrypted Virtualization) firmware update for AMD Family 17h models in the range 00h to 0fh

The previously identified CPU specific firmware blob file (in this example CPU family 22) needs to be built into the kernelː

KERNEL Single AMD firmware blob

Device Drivers  --->
    Generic Driver Options 
        (amd-ucode/microcode_amd_fam16h.bin) External firmware blobs to build into the kernel binary
        (/lib/firmware) Firmware blobs root directory

Warning
Every option must be set as built into the kernel, not as a kernel module.

Initrd

You can load the microcode with the initrd. This way the firmware blobs are not inside the kernel, which will instead look for them in the loaded initrd.

Kernel

In order to use the initrd, you have to enable it in the kernel:

KERNEL Initrd support enablement

General setup  --->
    [*] Initial RAM filesystem and RAM disk (initramfs/initrd) support

Firmware files preparation

First create the specified directory and cd into it. It doesn't have to be in /tmp but the kernel/x86/microcode part is necessary.

user $mkdir -p /tmp/amd-ucode/kernel/x86/microcode

user $cd /tmp/amd-ucode

Then we concatenate all the AMD firmware files into a single file. As before the path and filename of the output file must not be altered.

user $cat /lib/firmware/amd-ucode/microcode_amd*.bin > kernel/x86/microcode/AuthenticAMD.bin

Then we will create a cpio archive in /boot/amd-uc.img using bsdcpio from app-arch/libarchive:

root #echo kernel/x86/microcode/AuthenticAMD.bin | bsdcpio -o -H newc -R 0:0 > /boot/amd-uc.img

Alternatively, enable the initramfs USE flag to get /boot/amd-uc.img.

GRUB2 configuration

Since the image file /boot/amd-uc.img is one of the recognized ones by GRUB2 we just need to regenerate grub config.

root #grub-mkconfig -o /boot/grub/grub.cfg

Found linux image: /boot/vmlinuz-4.18.12
Found initrd image: /boot/amd-uc.img /boot/initramfs-4.18.12.img

It should show that it found the /boot/amd-uc.img file.

Building the kernel

Rebuild and install the kernel as usual.

Verification

After the next reboot with the new kernel, you should see a similar output:

user $dmesg | grep microcode

[    0.584603] microcode: microcode: updated early to new patch_level=0x06000832
[    0.868036] microcode: CPU0: patch_level=0x06000832
[    0.868116] microcode: CPU1: patch_level=0x06000832
[    0.868196] microcode: CPU2: patch_level=0x06000832
[    0.868277] microcode: CPU3: patch_level=0x06000832
[    0.868360] microcode: CPU4: patch_level=0x06000832
[    0.868451] microcode: CPU5: patch_level=0x06000832
[    0.868538] microcode: CPU6: patch_level=0x06000832
[    0.868619] microcode: CPU7: patch_level=0x06000832
[    0.868718] microcode: Microcode Update Driver: v2.01 <tigran@aivazian.fsnet.co.uk>, Peter Oruba

The first line contains the microcode: updated early log message in case a microcode update was performed during the boot.