How to include microcode in booster image?

[arun54321]

Microcode is included inside dracut images like this:

❯ _ lsinitrd /boot/initramfs-5.18.9-200.fc36.x86_64.img | ag "\.bin"
-rw-r--r--   1 root     root       106496 Mar 30 14:23 kernel/x86/microcode/GenuineIntel.bin

How can I include microcode when generating initrd image using booster?

[anatol]

The recommended way (at least at Arch) is to pack microcode in a separate image and load it before the initramfs. initrd /boot/cpu_manufacturer-ucode.img /boot/initramfs-linux.img. See https://wiki.archlinux.org/title/Microcode for more examples.

If you still want to put the microcode files into the image with extra_files: /path/to/microcode but booster itself does not do anything to load it.

[arun54321]

I use Fedora. So I cannot do the arch way.
Fedora doesn't have microcode.img file/package.

https://packages.fedoraproject.org/pkgs/microcode_ctl/microcode_ctl/fedora-36.html#files

[anatol]

A separate microcode image is a nicer cleaner/solution and Fedora/RHEL should definitely look at it.

Meantime we can look at a stopgap solution for it. Booster could detect the microcode file with code similar to following

get_ucode_file() {
    local family
    local model
    local stepping
    family=$(grep -E "cpu family" /proc/cpuinfo | head -1 | sed "s/.*:\ //")
    model=$(grep -E "model" /proc/cpuinfo | grep -v name | head -1 | sed "s/.*:\ //")
    stepping=$(grep -E "stepping" /proc/cpuinfo | head -1 | sed "s/.*:\ //")

    if [[ "$(get_cpu_vendor)" == "AMD" ]]; then
        if [[ $family -ge 21 ]]; then
            printf "microcode_amd_fam%xh.bin" "$family"
        else
            printf "microcode_amd.bin"
        fi
    fi
    if [[ "$(get_cpu_vendor)" == "Intel" ]]; then
        # The /proc/cpuinfo are in decimal.
        printf "%02x-%02x-%02x" "${family}" "${model}" "${stepping}"
    fi
}

and then put the file under /kernel/x86/microcode/{AuthenticAMD.bin,GenuineIntel.bin}

[anatol]

I just pushed a possible solution for this request to wip branch. Here is the change itself bad3624

I do not have a Fedora machine and unable to test the solution properly. @arun54321 would you be able to help with testing?

[arun54321]

I'm facing issues on installing cpuidv2 dependency. I will test it after I manage to compile booster-generator.

[anatol]

I looked at my solution I like it that much. I still think that a separate ucode image is a better solution even at Fedora.

So I went ahead and made a tool to generate ucode early boot images. @arun54321 please build https://github.com/anatol/ucode-image-gen, generate the ucode image as ./ucode-image-gen. It will produce ucode.img that you put into /boot, then modify your bootloader to include this image before the booster one.

[arun54321]

Not just fedora. Ubuntu and other popular distros use dracut, include microcode in initramfs.

I think including microcode inside initramfs is a better solution because some people use efistub loader and using a separate microcode image adds extra complexity.

[anatol]

because some people use efistub loader

According to the Arch wiki it should be as easy as adding an extra initrd= option

https://wiki.archlinux.org/title/Microcode#EFISTUB