Date: Wed, 21 Oct 2009 15:45:12 +0200
Message-Id: <1394846127@web.de>
MIME-Version: 1.0
From: Thomas Schlichter <thomas.schlichter@web.de>
To: Ingo Molnar <mingo@elte.hu>, Suresh Siddha <suresh.b.siddha@intel.com>
Cc: Jan Beulich <JBeulich@novell.com>,
       Arjan van de Ven <arjan@linux.intel.com>,
       dri-devel@lists.sourceforge.net, Robert Hancock <hancockrwd@gmail.com>,
       Henrique de Moraes Holschuh <hmh@hmh.eng.br>,
       "H. Peter Anvin" <hpa@zytor.com>, jbarnes@virtuousgeek.org,
       Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>,
       linux-kernel@vger.kernel.org, Ingo Molnar <mingo@redhat.com>,
       Thomas Gleixner <tglx@linutronix.de>,
       Thomas Hellstrom <thellstrom@vmware.com>, Tejun Heo <tj@kernel.org>,
       Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>, x86@kernel.org,
       Yinghai Lu <yinghai@kernel.org>
Subject: =?iso-8859-15?Q?Re:_[RFC_Patch]_use_MTRR_for_write_combining_if_PAT_is?=
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Suresh Siddha wrote:
> I think we can simplify this  by just using mtrr_add_page() and avoid
> all the complexity that comes with mtrr_add_unaligned().
> 
> pci_mmap_range() should call one mtrr_add_page() if the base and size
> are nicely aligned. Almost all the cases, this is the usage sequence
> here anyway.

Ingo Molnar wrote:
> Can we eliminate mtrr_add_unaligned() as Suresh suggested, and still 
> make it work on your testbox?

Yes, I had that in the first place, but Jan suggested to extend it to also
handle non-aligned, non-power-of-two cases:
  http://marc.info/?l=linux-kernel&m=125541951529918&w=2

So if it's OK for Jan, I'll reduce the functionality again and use mtrr_add()
instead. Btw. this simply means to drop mtrr_add_unaligned(), all the other
parts are still required for reference counting and a proper mtrr_del() on file
close.

Kind regards,
  Thomas
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