From mboxrd@z Thu Jan  1 00:00:00 1970
From: Ingo Molnar <mingo-X9Un+BFzKDI@public.gmane.org>
Subject: Re: [PATCH 0/2][concept RFC] x86: BIOS-save kernel log to disk upon
	panic
Date: Wed, 26 Jan 2011 13:58:13 +0100
Message-ID: <20110126125813.GA26952@elte.hu>
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To: "Ahmed S. Darwish" <darwish.07-Re5JQEeQqe8AvxtiuMwx3w@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?= 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>, 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>, Andrew Morton <akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@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>, Eric Biederman <ebiederm@xmission.c>
List-Id: linux-ide@vger.kernel.org


* Ahmed S. Darwish <darwish.07-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:

> - The latest approach (proposed by Linus) is to forget the disk: jump to
>   real-mode, but display the kernel log in a fancy format (with scroll
>   ups and downs) instead.
> 
>   Will re-initializing the VGA registers to their POST state be possible?
>   If not, what about a "fail-safe" VGA driver?
> 
> I'm most likely going to implement either the second or the third point,
> so I'd really appreciate some input.

The third one suggested by Linus is the most useful and most direct one IMO. Such a 
'oops mode' screen would be useful for regular kernel crashes as well.

Also, have you tried BIOS warm reset vector, which is supposed to reboot without 
clearing RAM contents - how well does it work in practice on typical laptops? If on 
crash we could reboot without memory getting cleared that would open up a vast area 
of space to store the kernel log into (RAM).

Thanks,

	Ingo