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Re: [Xen-devel] Odd mapping behavior with map_pages_to_xen

To: Arne Mejlholm <mejlholm@xxxxxxxxx>
Subject: Re: [Xen-devel] Odd mapping behavior with map_pages_to_xen
From: Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>
Date: Fri, 17 Mar 2006 08:47:48 +0000
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On 16 Mar 2006, at 19:05, Arne Mejlholm wrote:

If you build Xen with 'debug=y' option then I expect you'll find your code works fine. :-)

You expected correctly indeed. I take it that enabling debug either forces the mappings to be replaced (non-lazily) or does it switch entirely to 4kb pages?

There is no code to replace the mappings in non-idle pagetables. So it's the latter -- to support heap guard pages, we map the entire Xen heap with 4kB pages in debug builds.

In non-debug builds the superpages are used in all pagetables to map Xen heap. It's to improve TLB utilisation.

 -- Keir


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