linux-kernel - Re: [regression] microcode files missing in initramfs imgages from dracut (was Re: [PATCH] x86: Clean up remaining references to CONFIG_MICROCODE

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Message-ID: <CAHk-=wiV+NM+jLKbSj_Ej9RaXpu4akWV03G_wXyTSHZhArq1tg@mail.gmail.com>
Date:   Wed, 22 Nov 2023 12:35:54 -0800
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Borislav Petkov <bp@...en8.de>
Cc:     Linux regressions mailing list <regressions@...ts.linux.dev>,
        lukas.bulwahn@...il.com, dave.hansen@...ux.intel.com,
        hpa@...or.com, kernel-janitors@...r.kernel.org,
        linux-kernel@...r.kernel.org, mingo@...hat.com, tglx@...utronix.de,
        x86@...nel.org
Subject: Re: [regression] microcode files missing in initramfs imgages from
 dracut (was Re: [PATCH] x86: Clean up remaining references to CONFIG_MICROCODE_AMD)

On Wed, 22 Nov 2023 at 07:58, Borislav Petkov <bp@...en8.de> wrote:
>
> IMO, yes, we should not break userspace but dracut is special. And it
> parses willy nilly kernel internals which are not ABI to begin with.

I don't think the "dracut is special" is the thing that matters.

The real issue is that hey, if dracut in its incompetence doesn't
include the microcode on the initrd, that doesn't really matter much.
It's fairly easily fixable, and at worst it will mean that we end up
having CPU mitigations that aren't optimal. Since most of those are BS
anyway, it really doesn't seem critical.

Sure, it's a "regression" in that you don't get the microcode update
included, but from a user perspective things should still continue to
work.

End result: this seems to be pretty solidly a distro issue.

IOW, the whole "users are the only thing that matters" pretty much
means that it's a non-issue. Things continued to work, to the point
that I'm actually surprised anybody even noticed.

That said, I don't think some ELF note is the fix either. I think we
might as well leave it at CONFIG_MICROCODE. Maybe add a note in the
kernel Kconfig that this thing matters for dracut.

Dracut also checks for CONFIG_ACPI_INITRD_TABLE_OVERRIDE. It's a
similar "normal users don't care".

              Linus