linux-kernel - Re: ioremap_uc() followed by set_memory_wc()

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Message-ID: <CAB=NE6U91sMEXDdpu0BeL066j2EPho=owM-H=_8-4yCkWBVKbA@mail.gmail.com>
Date:	Wed, 22 Apr 2015 12:14:04 -0700
From:	"Luis R. Rodriguez" <mcgrof@...e.com>
To:	Doug Ledford <dledford@...hat.com>
Cc:	Jason Gunthorpe <jgunthorpe@...idianresearch.com>,
	Andy Lutomirski <luto@...capital.net>,
	Mike Marciniszyn <mike.marciniszyn@...el.com>,
	Mike Marciniszyn <infinipath@...el.com>,
	linux-rdma@...r.kernel.org, Andy Walls <awalls@...metrocast.net>,
	Toshi Kani <toshi.kani@...com>,
	"H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Hal Rosenstock <hal.rosenstock@...il.com>,
	Sean Hefty <sean.hefty@...el.com>,
	Suresh Siddha <sbsiddha@...il.com>,
	Rickard Strandqvist <rickard_strandqvist@...ctrumdigital.se>,
	Roland Dreier <roland@...estorage.com>,
	Juergen Gross <jgross@...e.com>,
	Mauro Carvalho Chehab <mchehab@....samsung.com>,
	Borislav Petkov <bp@...e.de>, Mel Gorman <mgorman@...e.de>,
	Vlastimil Babka <vbabka@...e.cz>,
	Davidlohr Bueso <dbueso@...e.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	Jean-Christophe Plagniol-Villard <plagnioj@...osoft.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	"Ville Syrj?l?" <syrjala@....fi>,
	Linux Fbdev development list <linux-fbdev@...r.kernel.org>,
	linux-media@...r.kernel.org, X86 ML <x86@...nel.org>
Subject: Re: ioremap_uc() followed by set_memory_wc() - burrying MTRR

On Wed, Apr 22, 2015 at 12:10 PM, Doug Ledford <dledford@...hat.com> wrote:
> On Wed, 2015-04-22 at 21:05 +0200, Luis R. Rodriguez wrote:
>
>> > > I'd also love to remove the driver if it turns out there are actually
>> > > no users. qib substantially replaces it except for a few very old
>> > > cards.
>> >
>> > To be precise, the split is that ipath powers the old HTX bus cards that
>> > only work in AMD systems,
>>
>> Do those systems have PAT support? CAn anyone check if PAT is enabled
>> if booted on a recent kernel?
>
> I don't have one of these systems any more.  The *only* one I ever had
> was a monster IBM box...I can't even find a reference to it any more.

Um, yeah if its so rare then I think the compromise proposed might
make sense, specially since folks were even *considering* seriously
removing this device driver. I'll send some patches to propose the
strategy explained to require booting with pat disabled.

 Luis
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