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Date: Thu, 27 Jan 2011 08:12:45 -0800
From: "H. Peter Anvin" <hpa@zytor.com>
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Subject: Re: [PATCH 0/2][concept RFC] x86: BIOS-save kernel log to disk upon
	panic
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To: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Willy Tarreau <wtarreau@hera.kernel.org>, Dirk Hohndel <hohndel@infradead.org>, =?ISO-8859-1?Q?Fr=E9d=E9ric_W?= =?ISO-8859-1?Q?eisbecker?= <fweisbec@gmail.com>, FBDEV-ML <linux-fbdev@vger.kernel.org>, IDE-ML <linux-ide@vger.kernel.org>, Randy Dunlap <rdunlap@xenotime.net>, James Bottomley <James.Bottomley@suse.de>, X86-ML <x86@kernel.org>, "Ahmed S. Darwish" <darwish.07@gmail.com>, Ingo Molnar <mingo@redhat.com>, Ingo Molnar <mingo@elte.hu>, Jeff Garzik <jgarzik@pobox.com>, Vivek Goyal <vgoyal@redhat.com>, Peter Zijlstra <a.p.zijlstra@chello.nl>, Dirk.Hohndel@intel.com, Borislav Petkov <bp@alien8.de>, Dave Jones <davej@redhat.com>, Thomas Gleixner <tglx@linutronix.de>, Mark Lord <kernel@teksavvy.com>, Arjan van de Ven <arjan@infradead.org>, Tony Luck <tony.luck@intel.com>, KEXEC-ML <kexec@lists.infradead.org>, LKML <linux-kernel@vger.kernel.org>, Haren Myneni <hbabu@us.ibm.com>, Tejun Heo <tj@kernel.org>, Andrew Morton <akpm@linux-foundation.org>, Linus Torvalds <torvalds@linux-foundation.org>, Willy Tarreau <w@1wt.eu>

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

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