linux-kernel - Re: BUG: early intel microcode update violating alignment rules

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Message-ID: <06991931-9f04-49fc-9ef7-ba23384aeb32@email.android.com>
Date:	Mon, 11 Aug 2014 11:48:25 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Henrique de Moraes Holschuh <hmh@....eng.br>,
	Borislav Petkov <bp@...en8.de>,
	Fenghua Yu <fenghua.yu@...el.com>
CC:	linux-kernel@...r.kernel.org
Subject: Re: BUG: early intel microcode update violating alignment rules

I don't think so.  I wouldn't count on that in the long run.

I'm having some discussions about this integrally at the moment.

On August 11, 2014 11:18:32 AM PDT, Henrique de Moraes Holschuh <hmh@....eng.br> wrote:
>On Mon, Aug 11, 2014, at 11:51, H. Peter Anvin wrote:
>> We could put a buffer in the initdata region (we really could use an
>> initbss region!) or in the brk.
>
>That sounds much better than the hideous crap I came up with.  The
>buffer would need to be at least 64KiB in size to be on the safe side. 
>The largest public microcode update ATM is 23KiB.
>
>I am not sure if we might need more than 64KiB: the Intel SDM mentions
>that in real mode the update data must not cross a segment boundary,
>and
>also must not exceed a segment limit.  I am a bit rusty on real mode,
>but doesn't that mean, in practice, that microcode update data size is
>limited in size to 64KiB?

-- 
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