From mboxrd@z Thu Jan  1 00:00:00 1970
From: ebiederm-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org (Eric W. Biederman)
Subject: Re: [PATCH 0/2][concept RFC] x86: BIOS-save kernel log to disk upon
	panic
Date: Thu, 27 Jan 2011 07:47:54 -0800
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In-Reply-To: <20110127114113.GB20279-X9Un+BFzKDI@public.gmane.org> (Ingo Molnar's message of "Thu,
	27 Jan 2011 12:41:13 +0100")
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To: Ingo Molnar <mingo-X9Un+BFzKDI@public.gmane.org>
Cc: Willy Tarreau <wtarreau-Dj75qbTlC0E76Z2rM5mHXA@public.gmane.org>, Dirk Hohndel <hohndel-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>, =?utf-8?B?RnLDqWTDqXJpYw==?= Weisbecker <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>, "H. Peter Anvin" <hpa-YMNOUZJC4hwAvxtiuMwx3w@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>, 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-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>, Tej
List-Id: linux-ide@vger.kernel.org

Ingo Molnar <mingo-X9Un+BFzKDI@public.gmane.org> writes:

> * H. Peter Anvin <hpa-YMNOUZJC4hwAvxtiuMwx3w@public.gmane.org> wrote:
>
>> On 01/26/2011 06:00 AM, Ingo Molnar wrote:
>> >
>> >I mean, use the warm reset vector to truly reset the box.
>> >
>> >Then, once a stable known-good kernel boots, *that* kernel can then recover all the
>> >log data which is sitting in a well-known place in RAM, automatically and
>> >transparently.
>> >
>> >Basically a bit like kexec, just more convenient and it also goes through the BIOS
>> >warm reset, so it might work better than kexec ...
>> >
>> 
>> The problem is that the BIOS will often wipe memory.
>
> 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.

Eric