Date: Sun, 3 Feb 2008 03:23:56 +0100
From: Andrea Arcangeli <andrea@qumranet.com>
To: Robin Holt <holt@sgi.com>
Cc: Christoph Lameter <clameter@sgi.com>, Avi Kivity <avi@qumranet.com>,
       Izik Eidus <izike@qumranet.com>, kvm-devel@lists.sourceforge.net,
       Peter Zijlstra <a.p.zijlstra@chello.nl>, steiner@sgi.com,
       linux-kernel@vger.kernel.org, linux-mm@kvack.org,
       daniel.blueman@quadrics.com
Subject: Re: [patch 2/4] mmu_notifier: Callbacks to invalidate address
	ranges
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On Fri, Feb 01, 2008 at 05:35:28PM -0600, Robin Holt wrote:
> 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.

I still hope I don't need to take any lock in _range_start and that
losing coherency (w/o risking global memory corruption but only
risking temporary userland data corruption thanks to the page pin) is
ok for KVM.

If I would have to take a lock in _range_start like XPMEM is forced to
do (GRU is by far not forced to it, if it would switch to my #v5) then
it would be a problem.
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