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Revision 19ee835cdb0b5a8eb11a68f25a51b8039d564488 authored by Chris Wilson on 29 June 2015, 13:01:19 UTC, committed by Daniel Vetter on 09 July 2015, 07:36:44 UTC 
drm/i915: Declare the swizzling unknown for L-shaped configurations
 
The old style of memory interleaving swizzled upto the end of the
first even bank of memory, and then used the remainder as unswizzled on
the unpaired bank - i.e. swizzling is not constant for all memory. This
causes problems when we try to migrate memory and so the kernel prevents
migration at all when we detect L-shaped inconsistent swizzling.
However, this issue also extends to userspace who try to manually detile
into memory as the swizzling for an individual page is unknown (it
depends on its physical address only known to the kernel), userspace
cannot correctly swizzle objects.

v2: Mark the global swizzling as unknown rather than adjust the value
reported to userspace.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=91105
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: stable@vger.kernel.org
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
1 parent dec4f79
Raw File
bad_memory.txt 
March 2008
Jan-Simon Moeller, dl9pf@gmx.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
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