Re: [patch 0/6] Guest page hinting version 6.

From: Hugh Dickins <hugh@veritas.com>
To: Jeremy Fitzhardinge <jeremy@goop.org>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>,
	linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org,
	virtualization@lists.osdl.org, akpm@linux-foundation.org,
	nickpiggin@yahoo.com.au, zach@vmware.com, frankeh@watson.ibm.com,
	rusty@rustcorp.com.au, andrea@qumranet.com, clameter@sgi.com,
	a.p.zijlstra@chello.nl, Keir Fraser <keir@xensource.com>,
	Ian Pratt <ian.pratt@xensource.com>
Subject: Re: [patch 0/6] Guest page hinting version 6.
Date: Thu, 13 Mar 2008 18:55:38 +0000 (GMT)	[thread overview]
Message-ID: <Pine.LNX.4.64.0803131848080.800@blonde.site> (raw)
In-Reply-To: <47D9754B.1030509@goop.org>

On Thu, 13 Mar 2008, Jeremy Fitzhardinge wrote:
> 
> My other concern is just correctness over time on the Linux side.  We already
> have enough trouble keeping things like the pte and page structure state in
> sync, with resulting rare data-loss bugs.  Adding another layer which only
> applies in specific environments raises the possibility for new bugs to be
> un-noticed for a long time.  How can we structure the VM changes to make sure
> that its robust in the face of maintenance?

Yes, that's the main concern, as whenever lots of subtlety is added.
I wonder if there's any chance of a CONFIG_DEBUG mode, which could be
run on anybody's x86 machine, without involving any virtualization, but
in which the PAGE_STATEs become essential to the correct working of the mm.

Hugh