linux-kernel - Re: Intel BIOS - Corrupted low memory at ffff880000004200

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Message-ID: <alpine.LFD.2.00.0907101504030.2768@localhost.localdomain>
Date:	Fri, 10 Jul 2009 15:05:19 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Alexey Fisher <bug-track@...her-privat.net>
cc:	Ingo Molnar <mingo@...e.hu>, Matthew Garrett <mjg59@...f.ucam.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	Arjan van de Ven <arjan@...radead.org>,
	"Pallipadi, Venkatesh" <venkatesh.pallipadi@...el.com>,
	Yinghai Lu <yinghai@...nel.org>,
	Suresh Siddha <suresh.b.siddha@...el.com>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Kernel Testers List <kernel-testers@...r.kernel.org>,
	"Richard A. Holden III" <aciddeath@...il.com>
Subject: Re: Intel BIOS - Corrupted low memory at ffff880000004200

On Fri, 10 Jul 2009, Alexey Fisher wrote:
> Ingo Molnar schrieb:
> > * Matthew Garrett <mjg59@...f.ucam.org> wrote:
> > 
> > > On Mon, Jul 06, 2009 at 06:24:47PM +0200, Alexey Fisher wrote:
> > > > Hallo Ingo, Richard.
> > > > 
> > > > I'm getting "Corrupted low memory" trace with my Intel DG45ID board
> > > > after resume. This board has different dmi-bios-vendor... so probably it
> > > > will be nice to have it in your patch.
> > > I'm beginning to think that we should be doing this on all hardware,
> > > perhaps with a kernel option to disable it for embedded devices that
> > > really need that 64K. The low-memory corruption issue seems to be very
> > > widespread.
> > 
> > The problem is that the BIOS corrupted memory that it also marked as
> > 'usable' in its E820 map it gave to the kernel. If that memory is not
> > usable, it should not have been marked as such. Also, some of the reports
> > showed corruption beyond this range so the workaround is not universal.
> > 
> > So i'd really like to know what is happening there, instead of just zapping
> > support for 64K of RAM on the majority of Linux systems.
> > 
> > We might end up doing the same thing in the end (i.e. disable that 64k of
> > RAM) - but it should be an informed decision, not a wild stab in the dark.
> > 
> > 	Ingo
> 
> If i make memory dump like "dd if=/dev/mem of=memdump.dd bs=64k count=1"
> before and after suspend. Will it help you find out whats happening.

The corrupted low memory printks contain the modifications. Can you
post them please ?

Thanks,

	tglx
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