linux-kernel - Re: [patch 2/4] mmu_notifier: Callbacks to invalidate address ranges

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Message-ID: <20080201233528.GE12099@sgi.com>
Date:	Fri, 1 Feb 2008 17:35:28 -0600
From:	Robin Holt <holt@....com>
To:	Christoph Lameter <clameter@....com>
Cc:	Robin Holt <holt@....com>, Andrea Arcangeli <andrea@...ranet.com>,
	Avi Kivity <avi@...ranet.com>, Izik Eidus <izike@...ranet.com>,
	kvm-devel@...ts.sourceforge.net,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>, steiner@....com,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	daniel.blueman@...drics.com
Subject: Re: [patch 2/4] mmu_notifier: Callbacks to invalidate address
	ranges

On Fri, Feb 01, 2008 at 03:19:32PM -0800, Christoph Lameter wrote:
> On Fri, 1 Feb 2008, Robin Holt wrote:
> 
> > We are getting this callout when we transition the pte from a read-only
> > to read-write.  Jack and I can not see a reason we would need that
> > callout.  It is causing problems for xpmem in that a write fault goes
> > to get_user_pages which gets back to do_wp_page that does the callout.
> 
> Right. You placed it there in the first place. So we can drop the code 
> from do_wp_page?

No, we need a callout when we are becoming more restrictive, but not
when becoming more permissive.  I would have to guess that is the case
for any of these callouts.  It is for both GRU and XPMEM.  I would
expect the same is true for KVM, but would like a ruling from Andrea on
that.

Thanks,
Robin
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