linux-kernel - Re: x86/microcode update on systems without INITRD

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Date:	Fri, 08 Jan 2016 11:46:28 +0000
From:	Måns Rullgård <mans@...sr.com>
To:	Borislav Petkov <bp@...e.de>
Cc:	Thomas Voegtle <tv@...96.de>,
	Markus Trippelsdorf <markus@...ppelsdorf.de>,
	linux-kernel@...r.kernel.org
Subject: Re: x86/microcode update on systems without INITRD

Borislav Petkov <bp@...e.de> writes:

> On Fri, Jan 08, 2016 at 11:18:51AM +0000, Måns Rullgård wrote:
>> Neither "depends on" nor "select" makes sense to me here.  The driver
>> apparently works without it,
>
> The driver works without it if you build your microcode into the kernel.
>
> There are use cases where building microcode into the kernel is *not* a
> viable option so we have to support both builtin microcode and microcode
> from the initrd.

How is an initrd different from a real filesystem as seen by the
microcode update driver?

>> and simply having BLK_DEV_INITRD enabled doesn't prevent improper
>> (according to some people) use of the driver. If updating microcode
>> is inherently unsafe when a real disk is mounted, the driver ought
>> to detect this and refuse the operation (possibly with an override
>> option).
>
> Huh, what?
>
> -ENOPARSE.

The objection against removing the dependency was that updating
microcode "late" isn't safe.  I don't see how turning on BLK_DEV_INITRD
stops anyone doing those allegedly unsafe updates anyway.

-- 
Måns Rullgård