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Message-ID: <1410385673.28990.313.camel@misato.fc.hp.com>
Date: Wed, 10 Sep 2014 15:47:53 -0600
From: Toshi Kani <toshi.kani@...com>
To: "H. Peter Anvin" <hpa@...or.com>
Cc: Andy Lutomirski <luto@...capital.net>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Arnd Bergmann <arnd@...db.de>,
"linux-mm@...ck.org" <linux-mm@...ck.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
Juergen Gross <jgross@...e.com>,
Stefan Bader <stefan.bader@...onical.com>,
Henrique de Moraes Holschuh <hmh@....eng.br>,
Yigal Korman <yigal@...xistor.com>,
Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
Subject: Re: [PATCH v2 2/6] x86, mm, pat: Change reserve_memtype() to handle
WT
On Wed, 2014-09-10 at 14:39 -0700, H. Peter Anvin wrote:
> On 09/10/2014 02:27 PM, Andy Lutomirski wrote:
> >>
> >> That's possible, but the only benefit is that we can enable WT on
> >> pre-PAT systems, which I do not think anyone cares now... WB & UC work
> >> on pre-PAT systems. WC & WT need PAT. I think this requirement is
> >> reasonable.
> >
> > It might end up being a cleanup, though. A whole bunch of
> > rarely-exercised if (!pat_enabled) things would go away.
> >
>
> Yes. Don't think of it as PAT vs non-PAT. Think of it as a specific
> set of cache types available on different processors. The fact that you
> may have to frob an MSR to initialize it is almost trivial in comparison.
Right.
Thanks,
-Toshi
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