linux-kernel - Re: [PATCH 2.6.24] mm: BadRAM support for broken memory

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Date:	Tue, 11 Mar 2008 21:00:59 +0100
From:	Jan-Simon Möller <dl9pf@....de>
To:	Johannes Weiner <hannes@...urebad.de>
Cc:	Len Brown <lenb@...nel.org>, "H. Peter Anvin" <hpa@...or.com>,
	Pavel Machek <pavel@....cz>, Jiri Kosina <jkosina@...e.cz>,
	Ingo Molnar <mingo@...e.hu>, devzero@....de,
	linux-kernel@...r.kernel.org, rick@...rein.org
Subject: Re: [PATCH 2.6.24] mm: BadRAM support for broken memory

V4 with checkpatch.pl done ...



Start of Documentation for BadRAM/memmap - 
Reference: http://lkml.org/lkml/2008/3/2/42

Signed-off-by: Jan-Simon Moeller <dl9pf@....de>


diff -up /dev/null bad-memory.txt
--- /dev/null   2007-09-21 21:12:45.000000000 +0200
+++ bad-memory.txt      2008-03-11 18:44:45.101344820 +0100
@@ -0,0 +1,56 @@
+March 2008
+Jan-Simon Moeller, dl9pf@....de
+
+
+How to deal with bad memory e.g. reported by memtest86+ ?
+#########################################################
+
+There are three possibilities I know of:
+
+1) Reinsert/swap the memory modules
+
+2) Buy new modules (best!) or try to exchange the memory
+   if you have spare-parts
+
+3) Use BadRAM or memmap
+
+This Howto is about number 3) .
+
+
+BadRAM
+######
+BadRAM is the actively developed and available as kernel-patch
+here:  http://rick.vanrein.org/linux/badram/
+
+It takes the patterns of memtest86+ as arguments to exclude the defective
+areas of the memory.
+
+Example: memtest86+ reported here errors at address 0x18691458, 0x18698424 and
+         some others. All had 0x1869xxxx in common, so I chose a pattern of
+         0x18690000,0xffff0000.
+         This means exclusion of the area from 0x18690000 to 0x1869ffff
+         (which is a block of 64k).
+         My kernel-cmdline was:  badram=0x18690000,0xffff0000
+
+There are efforts to bring BadRAM into mainline in some way, possibly using
+memmap internally (maybe 2.6.26 ?).
+Thread on lkml: http://lkml.org/lkml/2008/3/2/42
+
+For more details see the BadRAM documentation.
+
+
+memmap
+######
+memmap is already in the kernel and usable as kernel-parameter at boot-time.
+Its syntax is different and you may need to calculate the values by yourself!
+
+Syntax to exclude a memory area (see kernel-parameters.txt for details):
+memmap=<size>$<address>
+
+With the numbers of the example above:
+memmap=64K$0x18690000
+ or
+memmap=0x10000$0x18690000
+
+TODO: Multiple areas to exclude using memmap ?
+








Add example of usage to memmap - evolved from thread about BadRAM inclusion.

Signed-off-by: Jan-Simon Moeller <dl9pf@....de>


diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 533e67f..f25da88 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -1131,6 +1131,10 @@ and is between 256 and 4096 characters. It is defined in the file
 	memmap=nn[KMG]$ss[KMG]
 			[KNL,ACPI] Mark specific memory as reserved.
 			Region of memory to be used, from ss to ss+nn.
+			Example: Exclude memory from 0x18690000-0x1869ffff
+			         memmap=64K$0x18690000
+			         or
+			         memmap=0x10000$0x18690000
 
 	meye.*=		[HW] Set MotionEye Camera parameters
 			See Documentation/video4linux/meye.txt.
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