From mboxrd@z Thu Jan  1 00:00:00 1970
From: "H. Peter Anvin" <hpa-YMNOUZJC4hwAvxtiuMwx3w@public.gmane.org>
Subject: Re: [PATCH 0/2][concept RFC] x86: BIOS-save kernel log to disk upon
	panic
Date: Thu, 27 Jan 2011 08:12:45 -0800
Message-ID: <4D41997D.5070206@zytor.com>
References: <20110125134748.GA10051@laptop>	<AANLkTinU0KYiCd4p=z+=ojbkeEoT2G+CAYvdRU02KJEn@mail.gmail.com>	<20110126124954.GC24527@laptop>
	<20110126125813.GA26952@elte.hu>	<20110126133400.GA3399@laptop>
	<20110126140030.GB30064@elte.hu>	<4D40F5FD.6090507@zytor.com>
	<20110127114113.GB20279@elte.hu> <m1aaimxs9h.fsf@fess.ebiederm.org>
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To: "Eric W. Biederman" <ebiederm-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org>
Cc: Willy Tarreau <wtarreau-Dj75qbTlC0E76Z2rM5mHXA@public.gmane.org>, Dirk Hohndel <hohndel-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>, =?ISO-8859-1?Q?Fr=E9d=E9ric_W?= =?ISO-8859-1?Q?eisbecker?= <fweisbec-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>, FBDEV-ML <linux-fbdev-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>, IDE-ML <linux-ide-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>, Randy Dunlap <rdunlap-/UHa2rfvQTnk1uMJSBkQmQ@public.gmane.org>, James Bottomley <James.Bottomley-l3A5Bk7waGM@public.gmane.org>, X86-ML <x86-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>, "Ahmed S. Darwish" <darwish.07-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>, Ingo Molnar <mingo-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>, Ingo Molnar <mingo-X9Un+BFzKDI@public.gmane.org>, Jeff Garzik <jgarzik-e+AXbWqSrlAAvxtiuMwx3w@public.gmane.org>, Vivek Goyal <vgoyal-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>, Peter Zijlstra <a.p.zijlstra-/NLkJaSkS4VmR6Xm/wNWPw@public.gmane.org>, Dirk.Hohndel-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org, Borislav Petkov <bp-Gina5bIWoIWzQB+pC5nmwQ@public.gmane.org>, Dave Jones <davej-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>, Thomas Gleixner <tglx-hfZtesqFncYOwBW4kG4KsQ@public.gmane.org>, Mark Lord <kernel-R6A+fiHC8nRWk0Htik3J/w@public.gmane.org>, Arjan van de Ven <arjan-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>, Tony Luck <tony.luck-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>, KEXEC-ML <kexec-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org>, LKML <linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>, Haren Myneni <hbabu@us.>
List-Id: linux-ide@vger.kernel.org

On 01/27/2011 07:47 AM, Eric W. Biederman wrote:
>>
>> Yes - but at least a long time ago there used to be modi of reboot when the BIOS did
>> not do this. Whether that's possible at all with modern BIOSen is a
>> big question ...
>
> As I recall that was how you went from 32bit mode to 16bit real mode.
> The issue is that mode never reset the hardware it simply changed the
> cpu mode.
>

Quite correct.  It doesn't just bypass the memory wipe, it bypasses the 
entire POST.

	-hpa