linux-kernel - Early loading of microcode updates with all firmware

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Date:   Fri, 30 Jun 2017 12:44:43 +0200
From:   Paul Menzel <pmenzel@...gen.mpg.de>
To:     Borislav Petkov <bp@...en8.de>, linux-kernel@...r.kernel.org
Cc:     Fenghua Yu <fenghua.yu@...el.com>
Subject: Early loading of microcode updates with all firmware

Dear Borislav,

Thank you for recently updating the document *Early load microcode* [1].

My goal is to include all microcode updates from AMD and Intel, as the 
image is supposed to run on several systems.

Therefore, I included the files in the initramfs image, under 
`/lib/firmware`, and selected the microcode related Kconfig options.

```
$ grep MICROCODE /boot/config-4.11.7.mx64.161
CONFIG_MICROCODE=y
CONFIG_MICROCODE_INTEL=y
CONFIG_MICROCODE_AMD=y
CONFIG_MICROCODE_OLD_INTERFACE=y
```

But, the microcode is not updated. For example, I have to manually run 
the command below.

```
$ echo 1 | sudo tee /sys/devices/system/cpu/microcode/reload
```

Reading the document, that method is not explicitly mentioned there, so 
I guess it’s not supported.

So two question. If I want to add it to the initramfs image, the 
document says to prepend the updates. But I am unclear how to create 
`microcode.bin` to contain all the files in 
`/lib/firmware/intel-ucode/`, and then the ones for AMD devices. Do I 
just concatenate both?

Regarding the section *Builtin microcode*, it would be quite cumbersome 
to list all the microcode files. It looks like wildcards like `*` are 
not supported. At least the build breaks, if `intel-ucode/*` is used in 
the prompt.

Kind regards,

Paul

[1] https://www.kernel.org/doc/Documentation/x86/early-microcode.txt