linux-kernel - Re: [PATCH v2 6/6] x86, pat: Update documentation for WT changes

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Message-ID: <1410384895.28990.312.camel@misato.fc.hp.com>
Date:	Wed, 10 Sep 2014 15:34:55 -0600
From:	Toshi Kani <toshi.kani@...com>
To:	Andy Lutomirski <luto@...capital.net>
Cc:	"H. Peter Anvin" <hpa@...or.com>,
	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 6/6] x86, pat: Update documentation for WT changes

On Wed, 2014-09-10 at 13:29 -0700, Andy Lutomirski wrote:
> On Wed, Sep 10, 2014 at 1:12 PM, Toshi Kani <toshi.kani@...com> wrote:
> > On Wed, 2014-09-10 at 11:30 -0700, Andy Lutomirski wrote:
> >> On Wed, Sep 10, 2014 at 9:51 AM, Toshi Kani <toshi.kani@...com> wrote:
> >> > +Drivers may map the entire NV-DIMM range with ioremap_cache and then change
> >> > +a specific range to wt with set_memory_wt.
> >>
> >> That's mighty specific :)
> >
> > How about below?
> >
> > Drivers may use set_memory_wt to set WT type for cached reserve ranges.
> 
> Do they have to be cached?

Yes, set_memory_xyz only supports WB->type->WB transition.

> How about:
> 
> Drivers may call set_memory_wt on ioremapped ranges.  In this case,
> there is no need to change the memory type back before calling
> iounmap.
> 
> (Or only on cached ioremapped ranges if that is, in fact, the case.)

Sounds good.  Yes, I will use cashed ioremapped ranges.

Thanks,
-Toshi


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