linux-kernel - Re: [kvm-devel] [PATCH] export notifier #1

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Message-Id: <1201044989.6807.46.camel@pasglop>
Date:	Wed, 23 Jan 2008 10:36:29 +1100
From:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
To:	Christoph Lameter <clameter@....com>
Cc:	Andrea Arcangeli <andrea@...ranet.com>,
	Avi Kivity <avi@...ranet.com>, Izik Eidus <izike@...ranet.com>,
	Andrew Morton <akpm@...l.org>, Nick Piggin <npiggin@...e.de>,
	kvm-devel@...ts.sourceforge.net, steiner@....com,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	daniel.blueman@...drics.com, holt@....com,
	Hugh Dickins <hugh@...itas.com>
Subject: Re: [kvm-devel] [PATCH] export notifier #1


On Tue, 2008-01-22 at 12:34 -0800, Christoph Lameter wrote:
> 
> - Notifiers are called *after* we tore down ptes. At that point pages
>   may already have been freed and reused. This means that there can
>   still be uses of the page by the user of mmu_ops after the OS has
>   dropped its mapping. IMHO the foreign entity needs to drop its
>   mappings first. That also ensures that the entities operated
>   upon continue to exist.

That's definitely an issue. Maybe having the foreign entity get a
reference to the page and drop it when it unmaps would help ?

> - anon_vma/inode and pte locks are held during callbacks.

So how does that fix the problem of sleeping then ?

Ben.


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