linux-kernel - Re: [PATCH v2] x86: PAT: Documentation: rewrite "MTRR effects on PAT / non-PAT systems"

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Message-ID: <20160305010346.GW25240@wotan.suse.de>
Date:	Sat, 5 Mar 2016 02:03:46 +0100
From:	"Luis R. Rodriguez" <mcgrof@...nel.org>
To:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>, bp@...en8.de
Cc:	"Luis R. Rodriguez" <mcgrof@...nel.org>, mingo@...nel.org,
	tglx@...utronix.de, hpa@...or.com, toshi.kani@...com,
	airlied@...hat.com, benh@...nel.crashing.org, mst@...hat.com,
	vinod.koul@...el.com, jgross@...e.com, daniel.vetter@...ll.ch,
	luto@...capital.net, davem@...emloft.net, ben@...adent.org.uk,
	benjamin.poirier@...il.com, linux-fbdev@...r.kernel.org,
	linux-arch@...r.kernel.org, linux-kernel@...r.kernel.org,
	x86@...nel.org, linux-doc@...r.kernel.org, corbet@....net
Subject: Re: [PATCH v2] x86: PAT: Documentation: rewrite "MTRR effects on PAT
 / non-PAT systems"

On Fri, Mar 04, 2016 at 04:03:04PM -0800, Paul E. McKenney wrote:
> On Fri, Mar 04, 2016 at 02:45:01PM -0800, Luis R. Rodriguez wrote:
> > The current documentation refers to using set_memory_wc() as a
> > possible hole strategy when you have overlapping ioremap() regions,
> > that's incorrect as set_memory_*() helpers can only be used on RAM,
> > not IO memory. Using set_memory_wc() will not fail, that's a problem
> > which must be corrected in the future. This fixes that, and updates
> > the documention to *strongly* discourage overlapping ioremap() memory
> > uses, but also documents a possible solution should there really be
> > no other option to remain compatible on both PAT and MTRR memory
> > constarained systems. While at it, this provides some same guidlines
> > to system designers to remain sane and compatible on both PAT and
> > non-PAT systems.
> > 
> > As per Toshi this also fixes the table for the effective memory type
> > when using MTRR WC on PAT UC- to WC.
> > 
> > Signed-off-by: Luis R. Rodriguez <mcgrof@...nel.org>
> 
> And I was really confused during my earlier reply.  For some reason
> I read the filename as memory-barriers.txt.
> 
> This one is not mine.  Too much time in standards committee meetings,
> I guess.  ;-)

Heh, OK yeah I was confused why you wanted to pick it up but played along.
Boris, can this go through you as its a follow up that previously went
through you ?

  Luis