linux-kernel - Re: [patch] my mmu notifiers

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Message-ID: <20080220010941.GR7128@v2.random>
Date:	Wed, 20 Feb 2008 02:09:41 +0100
From:	Andrea Arcangeli <andrea@...ranet.com>
To:	Nick Piggin <npiggin@...e.de>
Cc:	akpm@...ux-foundation.org, Robin Holt <holt@....com>,
	Avi Kivity <avi@...ranet.com>, Izik Eidus <izike@...ranet.com>,
	kvm-devel@...ts.sourceforge.net,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	general@...ts.openfabrics.org,
	Steve Wise <swise@...ngridcomputing.com>,
	Roland Dreier <rdreier@...co.com>,
	Kanoj Sarcar <kanojsarcar@...oo.com>, steiner@....com,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	daniel.blueman@...drics.com, Christoph Lameter <clameter@....com>
Subject: Re: [patch] my mmu notifiers

On Wed, Feb 20, 2008 at 12:11:57AM +0100, Nick Piggin wrote:
> Sorry, I realise I still didn't get this through my head yet (and also
> have not seen your patch recently). So I don't know exactly what you
> are doing...

The last version was posted here:

http://marc.info/?l=kvm-devel&m=120321732521533&w=2

> But why does _anybody_ (why does Christoph's patches) need to invalidate
> when they are going to be more permissive? This should be done lazily by
> the driver, I would have thought.

This can be done lazily by the driver yes. The place where I've an
invalidate_pages in mprotect however can also become less permissive.
It's simpler to invalidate always and it's not guaranteed the
secondary mmu page fault is capable of refreshing the spte across a
writeprotect fault. In the future this can be changed to
mprotect_pages though, so no page fault will happen in the secondary
mmu.
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