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

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Date:	Tue, 20 Oct 2009 22:35:12 +0200
From:	Thomas Schlichter <thomas.schlichter@....de>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Jan Beulich <JBeulich@...ell.com>,
	Suresh Siddha <suresh.b.siddha@...el.com>,
	arjan@...ux.intel.com, dri-devel@...ts.sourceforge.net,
	hancockrwd@...il.com, hmh@....eng.br, hpa@...or.com,
	jbarnes@...tuousgeek.org, jeremy.fitzhardinge@...rix.com,
	linux-kernel@...r.kernel.org, mingo@...hat.com, tglx@...utronix.de,
	thellstrom@...are.com, tj@...nel.org,
	venkatesh.pallipadi@...el.com, x86@...nel.org, yinghai@...nel.org
Subject: Re: [RFC Patch] use MTRR for write combining if PAT is not available

Ingo Molnar wrote:
> * Thomas Schlichter <thomas.schlichter@....de> wrote:
> > > or Perhaps just try to add mtrr only for the pci mmap case like the
> > > 4th patch in this series..
> >
> > I'd prefer this! ;-)
> 
> Hm, we could perhaps do that - but i think we should only do that on
> systems that have PAT disabled.

The patch I sent should do exactly that.

> Which brings up the question of how to properly QA such a narrow segment
> of the market. Maybe disabling CONFIG_X86_PAT should enable that logic
> too.

When CONFIG_X86_PAT is disabled, pat_enabled is 0, and thus my new code should 
be active. Or do I miss something?

What do you think about the latest version of my patch series I just sent?

Kind regards,
  Thomas
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