linux-kernel - Re: [RFC Patch] use MTRR for write combining if PAT is not available

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Message-ID: <20091011185114.GB18578@khazad-dum.debian.net>
Date:	Sun, 11 Oct 2009 15:51:14 -0300
From:	Henrique de Moraes Holschuh <hmh@....eng.br>
To:	Arjan van de Ven <arjan@...ux.intel.com>
Cc:	Thomas Schlichter <thomas.schlichter@....de>,
	linux-kernel@...r.kernel.org,
	Thomas Hellstrom <thellstrom@...are.com>
Subject: Re: [RFC Patch] use MTRR for write combining if PAT is not
 available

On Fri, 09 Oct 2009, Arjan van de Ven wrote:
> >I've found a problem with X.org not setting up MTRR for the
> >framebuffer memory. After I investigated I think this is not a
> >X.org problem, but a kernel issue.
> 
> is there any CPU left that does not support PAT ?

A few million of them.  Like every Centrino laptop out there, unless the
kernel blacklist for PAT on Intel CPUs is wrong.

> eg in other words, should we try instead to get PAT working for you?

Is it even possible?  Can you get Intel to fix my Pentium M?  I'd be quite
happy to test any microcode updates you send my way :)

As things stand right now, you can assume PAT will be there in 2015 or
thereabouts.  Machine models that can run Linux have a service life of
around 15 years.

-- 
  "One disk to rule them all, One disk to find them. One disk to bring
  them all and in the darkness grind them. In the Land of Redmond
  where the shadows lie." -- The Silicon Valley Tarot
  Henrique Holschuh
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