linux-kernel - Re: [PATCH 03/35] xen: document Xen is using an unused bit for the pagetables

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Date:	Tue, 29 May 2012 10:10:49 -0400
From:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To:	Andrea Arcangeli <aarcange@...hat.com>
Cc:	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	Hillf Danton <dhillf@...il.com>, Dan Smith <danms@...ibm.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...e.hu>, Paul Turner <pjt@...gle.com>,
	Suresh Siddha <suresh.b.siddha@...el.com>,
	Mike Galbraith <efault@....de>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Lai Jiangshan <laijs@...fujitsu.com>,
	Bharata B Rao <bharata.rao@...il.com>,
	Lee Schermerhorn <Lee.Schermerhorn@...com>,
	Rik van Riel <riel@...hat.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Srivatsa Vaddagiri <vatsa@...ux.vnet.ibm.com>,
	Christoph Lameter <cl@...ux.com>
Subject: Re: [PATCH 03/35] xen: document Xen is using an unused bit for the
 pagetables

On Sat, May 26, 2012 at 05:59:12PM +0200, Andrea Arcangeli wrote:
> Hi Konrad,
> 
> On Fri, May 25, 2012 at 04:26:56PM -0400, Konrad Rzeszutek Wilk wrote:
> > On Fri, May 25, 2012 at 07:02:07PM +0200, Andrea Arcangeli wrote:
> > > Xen has taken over the last reserved bit available for the pagetables
> > > which is set through ioremap, this documents it and makes the code
> > > more readable.
> > 
> > Andrea, my previous respone had a question about this - was wondering
> > if you had a chance to look at that in your busy schedule and provide
> > some advice on how to remove the _PAGE_IOMAP altogether?
> 
> I read you response but I didn't look into the P2M tree and
> xen_val_pte code yet sorry. Thanks for looking into this, if it's
> possible to remove it without downsides, it would be a nice

Yeah, I am not really thrilled about it.

> cleanup. It's not urgent though, we're not running out of reserved
> pte bits yet :).

Oh, your git comment says "the last reserved bit". Let me
look through all your patches to see how the AutoNUMA code works -
I am probably just missing something simple.
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