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

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Date:	Wed, 10 Sep 2014 14:12:13 -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 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.

> It's also not all that informative.  Are you supposed to set the
> memory back before iounmapping?  

Setting back to WB before iounmap is not required, but set_memory_wb is
used when it wants to put it back to WB before unmapping.

> Can you do this with set_memory_wc on
> an uncached mapping?

The table lists interfaces and their intended usage.  Using
set_memory_wc on an uncached mapping probably works, but is not an
intended use.

Thanks,
-Toshi

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