linux-kernel - Re: [PATCH] panic.c: export panic_on

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Message-ID: <20091012191824.GL17138@elte.hu>
Date:	Mon, 12 Oct 2009 21:18:24 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Carl-Daniel Hailfinger <c-d.hailfinger.devel.2006@....net>
Cc:	David Woodhouse <dwmw2@...radead.org>,
	Artem Bityutskiy <dedekind1@...il.com>,
	LKML <linux-kernel@...r.kernel.org>,
	"Koskinen Aaro (Nokia-D/Helsinki)" <aaro.koskinen@...ia.com>,
	linux-mtd <linux-mtd@...ts.infradead.org>,
	Simon Kagstrom <simon.kagstrom@...insight.net>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Alan Cox <alan@...rguk.ukuu.org.uk>
Subject: Re: [PATCH] panic.c: export panic_on_oops


* Carl-Daniel Hailfinger <c-d.hailfinger.devel.2006@....net> wrote:

> > I wish it worked on any of the 10+ x86 systems i have. Is there 
> > anyone who'd be interested in exploring whether warm BIOS reboots 
> > work _anywhere_?
> 
> AFAIK memory clearing is default off in coreboot for non-ECC RAM and 
> default on for ECC RAM (to avoid parity errors on read, but that can 
> probably be worked around). Unless I'm mistaken, the SeaBIOS BIOS 
> compatibility layer on top of coreboot doesn't erase RAM at all, so 
> contents can survive.
>
> No idea about classic AMI/Award/Phoenix/Insyde/whatever BIOS, though.

I wouldnt mind to support this for coreboot too, but it will only be 
practical if there's at least one standard BIOS out of the many i run 
that supports warm reboot in practice ...

Can try a test-patch on all of those systems btw. - we do support 
warm-reboot on x86 in arch/x86/kernel/reboot.c:

        /* Write 0x1234 to absolute memory location 0x472.  The BIOS reads
           this on booting to tell it to "Bypass memory test (also warm
           boot)".  This seems like a fairly standard thing that gets set by
           REBOOT.COM programs, and the previous reset routine did this
           too. */
        *((unsigned short *)0x472) = reboot_mode;

But someone would have to come up with a test-patch to prove whether it 
works really works.

	Ingo
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