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

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Date:	Fri, 10 Jul 2009 14:16:49 +0200
From:	Alexey Fisher <bug-track@...her-privat.net>
To:	Ingo Molnar <mingo@...e.hu>
CC:	Matthew Garrett <mjg59@...f.ucam.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	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

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.
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