linux-kernel - Re: Corrupted low memory in v3.9+

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Message-ID: <5281707D.1040604@linux.intel.com>
Date:	Mon, 11 Nov 2013 16:04:13 -0800
From:	"H. Peter Anvin" <hpa@...ux.intel.com>
To:	Ingo Molnar <mingo@...nel.org>
CC:	Olof Johansson <olof@...om.net>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: Corrupted low memory in v3.9+

On 11/11/2013 03:31 PM, H. Peter Anvin wrote:
> On 11/11/2013 03:35 AM, Ingo Molnar wrote:
> 
> Oops!  I had misunderstood how the checker worked -- I thought it
> checked the *reserved* memory, but it in fact reserves memory
> *independently* and then checks it.
> 

And now I understand why I had that misconception:

> 	  Periodically check for memory corruption in low memory, which
> 	  is suspected to be caused by BIOS.  Even when enabled in the
> 	  configuration, it is disabled at runtime.  Enable it by
> 	  setting "memory_corruption_check=1" on the kernel command
> 	  line.  By default it scans the low 64k of memory every 60
> 	  seconds; see the memory_corruption_check_size and
> 	  memory_corruption_check_period parameters in
> 	  Documentation/kernel-parameters.txt to adjust this.

This makes it sound like it scans the low 64K when it is turned on, i.e.
the bit that is reserved by default.

I think we should change that default too to 640K.  I will post a
patchset shortly.

	-hpa



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