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

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Message-ID: <4A5753E8.9040704@fisher-privat.net>
Date:	Fri, 10 Jul 2009 16:44:56 +0200
From:	Alexey Fisher <bug-track@...her-privat.net>
To:	Thomas Gleixner <tglx@...utronix.de>
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

Thomas Gleixner schrieb:
> 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

I dumped all between 0000000 - 00ffff0
and there is changes at:
0004200 ->  this know one
003c000 - 003fff0 -> this was empty and now it looks like VBIOS
00d18a0 -> i don't know

cat /proc/iomem
00000000-0000ffff : reserved
00010000-0009e7ff : System RAM
0009e800-0009ffff : reserved
000e0000-000fffff : reserved
00100000-bd90dfff : System RAM
   01000000-014b1f1b : Kernel code
   014b1f1c-0171265f : Kernel data
   01794000-01842c07 : Kernel bss
.....
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