mtrr registers with >= 4GB ram

mtrr registers with >= 4GB ram

[Rann Bar-On]

As documented at https://bugs.launchpad.net/linux/+bug/210780 and 
http://www.rage3d.com/board/showthread.php?t=33821469 (as well as other 
places - google 4gb mtrr bug), the kernel appears to misdetect the mtrr 
registers on many machines with 4gb ram, causing all sorts of issues - 
especially with video drivers in X.  It is possible to rewrite the correct 
registers using a pretty hackish script, but the bug should probably be 
fixed at the kernel level.

Please CC me personally when replying, as I'm not on LKML.  I'd be happy 
to try out patches if such come along :)

Thanks,
Rann

Re: mtrr registers with >= 4GB ram

[Yinghai Lu]

On Wed, Jul 2, 2008 at 7:55 AM, Rann Bar-On <rb6@duke.edu> wrote:
> As documented at https://bugs.launchpad.net/linux/+bug/210780 and
> http://www.rage3d.com/board/showthread.php?t=33821469 (as well as other
> places - google 4gb mtrr bug), the kernel appears to misdetect the mtrr
> registers on many machines with 4gb ram, causing all sorts of issues -
> especially with video drivers in X.  It is possible to rewrite the correct
> registers using a pretty hackish script, but the bug should probably be
> fixed at the kernel level.
>
> Please CC me personally when replying, as I'm not on LKML.  I'd be happy to
> try out patches if such come along :)

please try tip/master
http://people.redhat.com/mingo/tip.git/readme.txt

we have some patches there ...
      x86: mtrr cleanup for converting continuous to discrete layout, v8
      x86: mtrr cleanup for converting continuous to discrete layout v8 - fix
      x86: mtrr cleanup for converting continuous to discrete - auto detect v4
      x86: mtrr cleanup for converting continuous to discrete layout - fix #2

YH