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

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Date:	Wed, 21 Oct 2009 16:14:44 +0100
From:	"Jan Beulich" <JBeulich@...ell.com>
To:	"Thomas Schlichter" <thomas.schlichter@....de>
Cc:	"Jeremy Fitzhardinge" <jeremy.fitzhardinge@...rix.com>,
	"Ingo Molnar" <mingo@...e.hu>,
	"Robert Hancock" <hancockrwd@...il.com>,
	"Henrique de Moraes Holschuh" <hmh@....eng.br>,
	"Suresh Siddha" <suresh.b.siddha@...el.com>,
	"Venkatesh Pallipadi" <venkatesh.pallipadi@...el.com>,
	"Tejun Heo" <tj@...nel.org>, <x86@...nel.org>,
	"Yinghai Lu" <yinghai@...nel.org>,
	"Thomas Gleixner" <tglx@...utronix.de>,
	"Arjan van de Ven" <arjan@...ux.intel.com>,
	<dri-devel@...ts.sourceforge.net>,
	"Ingo Molnar" <mingo@...hat.com>, <linux-kernel@...r.kernel.org>,
	<jbarnes@...tuousgeek.org>,
	"Thomas Hellstrom" <thellstrom@...are.com>,
	"H. Peter Anvin" <hpa@...or.com>
Subject: Re: [RFC Patch] use MTRR for write combining if PAT is not 
	 available

>>> Thomas Schlichter <thomas.schlichter@....de> 21.10.09 16:38 >>>
>Hmm, as far as I see mtrr_add() and mtrr_add_page() already check these
>constraints. Do you want me to check them additionally? Or do you want to
>completely fail the mmap() if these constraints are violated?

I'd say you should check it explicitly in the caller, to avoid the warning
message being printed otherwise.

>I'd let mmap() succeed even if the mtrr_add() fails...

Yes, of course.

Jan

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