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

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Message-Id: <4AD6EFD7020000780001A067@vpn.id2.novell.com>
Date:	Thu, 15 Oct 2009 08:48:07 +0100
From:	"Jan Beulich" <JBeulich@...ell.com>
To:	"Thomas Schlichter" <thomas.schlichter@....de>
Cc:	"Jeremy Fitzhardinge" <jeremy.fitzhardinge@...rix.com>,
	"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> 14.10.09 21:14 >>>
>I added a function mtrr_add_unaligned() that tries to create as many MTRR 
>entries as necessary, beginning with the biggest regions. It does not check 
>the return values of each mtrr_add(), nor does it return the indexes of the 
>created MTRR entries. So it seems to be only useful with increment=false. Or 
>do you have a better idea?

I don't have immediate thoughts on how to address this, but nevertheless
I continue to think that the issue must be solved in some way, even more
that now you may be leaking multiple MTRRs.

Jan

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