linux-kernel - Re: x86, microcode: BUG: microcode update that changes x86

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Message-ID: <20140925155044.GB28201@nazgul.tnic>
Date:	Thu, 25 Sep 2014 17:50:44 +0200
From:	Borislav Petkov <bp@...en8.de>
To:	Henrique de Moraes Holschuh <hmh@....eng.br>
Cc:	Chuck Ebbert <cebbert.lkml@...il.com>,
	Andy Lutomirski <luto@...capital.net>,
	"H. Peter Anvin" <hpa@...or.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: x86, microcode: BUG: microcode update that changes x86_capability

On Thu, Sep 25, 2014 at 12:30:06PM -0300, Henrique de Moraes Holschuh wrote:
> Userspace can install the microcode only inside the initramfs, if it wants
> to avoid it being loaded later.  It is not even too difficult to do so.

Hmm, so in thinking about this more, what we need to do on all kernels
should be something along those lines (if I'm not missing something,
that is):


	if (early microcode loading support) {
		install microcode into initramfs;
	}

	install microcode into /lib/firmware/...;
	tell the user to reboot;

On the next reboot, everything gets loaded automatically.

Of course, user needs to make sure that the microcode loader module gets
loaded during boot. If its built-in, we're fine.

-- 
Regards/Gruss,
    Boris.
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