Re: Intel BIOS - Corrupted low memory at ffff880000004200

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Thomas Gleixner schrieb:
On Fri, 10 Jul 2009, Alexey Fisher wrote:
Ingo Molnar schrieb:
* Matthew Garrett <mjg59@xxxxxxxxxxxxx> 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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