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

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Message-Id: <200910202154.20195.thomas.schlichter@web.de>
Date:	Tue, 20 Oct 2009 21:54:20 +0200
From:	Thomas Schlichter <thomas.schlichter@....de>
To:	"Jan Beulich" <JBeulich@...ell.com>
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

Jan Beulich wrote:
> Functionality-wise this looks fine to me; whether the core sysfs changes
> are acceptable I can't judge, though.

OK, I think I should have addressed your comments. Unfortunately I had to use 
a little "hack" to make pci_mmap_page_range() work for sysfs and proc. I 
placed a "private" pointer in the beginning of both per-file private 
structures. So this pointer can be accessed independent from the caller. I 
hope this is acceptable.

I dropped the ioremap() and set_memory_wc() patches, I could not implement 
reference counting for them and it may interact too much with existing GPU 
drivers.

Again, this series should not change the current behavior if either MTRR is 
disabled or PAT is enabled. But it helps in the case that MTRR is enabled and 
PAT is not available.

What should be done now to get this series on the right "track"?

Kind regards,
  Thomas

View attachment "0004-Use-MTRR-for-pci_mmap_resource_wc-if-PAT-is-not-avai.patch" of type "text/x-patch" (5518 bytes)

View attachment "0001-Add-new-mtrr_add_unaligned-function.patch" of type "text/x-patch" (2756 bytes)

View attachment "0002-Make-num_var_ranges-accessible-outside-MTRR-code.patch" of type "text/x-patch" (1638 bytes)

View attachment "0003-Provide-per-file-private-data-for-bin-sysfs-files.patch" of type "text/x-patch" (2158 bytes)