From mboxrd@z Thu Jan  1 00:00:00 1970
From: Olaf Hering <olaf@aepfle.de>
Subject: Re: mark pages in p2m_ram_paging_out state read-only
Date: Thu, 24 Nov 2011 19:24:15 +0100
Message-ID: <20111124182415.GA24717@aepfle.de>
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To: Tim Deegan <tim@xen.org>
Cc: xen-devel@lists.xensource.com, Andres Lagar-Cavilla <andres@lagarcavilla.org>
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On Thu, Nov 24, Tim Deegan wrote:

> > Is this a good idea? If the guest is accessing the page, then paging out
> > should stop immediately. We're risking complex races for a tiny tiny gain.
> 
> I don't think that this would introduce any new races, but yes - this is
> probably a hint that this page is a poor candidate to be paged out.
> We might as well abandon the page-out rather than probably having to
> page it back in immediately.

In the current state there will be a stall in the guest due to the
fault, until the page comes back. 
With this change the guest can still make progress. 
Can the read-execute access be detected anyway to stop paging?