linux-kernel - document memmap option better and help people with bad memory

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Message-ID: <20080313080804.GA19808@elf.ucw.cz>
Date:	Thu, 13 Mar 2008 09:08:04 +0100
From:	Pavel Machek <pavel@....cz>
To:	dl9pf@....de, kernel list <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...l.org>,
	Trivial patch monkey <trivial@...nel.org>
Subject: document memmap option better and help people with bad memory

Provide example for memmap exclude option (it is slightly strange an
non-trivial) and provide nice small HOWTO for people with bad memory.

Signed-off-by: Jan-Simon Moeller <dl9pf@....de>
Signed-off-by: Pavel Machek <pavel@...e.cz>

---
commit ec630f2291d7a3a154e22fa54cd74e5f6aa47f9a
tree 9cf33f9fcda3ea363061acebc971c37815f6c907
parent 456fc99ea933d38466ee25681908868cde3425c5
author Pavel <pavel@....ucw.cz> Thu, 13 Mar 2008 09:06:15 +0100
committer Pavel <pavel@....ucw.cz> Thu, 13 Mar 2008 09:06:15 +0100

 Documentation/bad_memory.txt        |   45 +++++++++++++++++++++++++++++++++++
 Documentation/kernel-parameters.txt |    4 +++
 2 files changed, 49 insertions(+), 0 deletions(-)

diff --git a/Documentation/bad_memory.txt b/Documentation/bad_memory.txt
new file mode 100644
index 0000000..df84162
--- /dev/null
+++ b/Documentation/bad_memory.txt
@@ -0,0 +1,45 @@
+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/
+
+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 slightly strange 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>
+
+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.
+
+With the numbers of the example above:
+memmap=64K$0x18690000
+ or
+memmap=0x10000$0x18690000
+
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 533e67f..f25da88 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -1131,6 +1131,10 @@ and is between 256 and 4096 characters. 
 	memmap=nn[KMG]$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.

-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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