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RE: [Xen-devel] x86-64 machine_to_phys vs NX bit

To: "Nakajima, Jun" <jun.nakajima@xxxxxxxxx>, "Keir Fraser" <Keir.Fraser@xxxxxxxxxxxx>, "Rik van Riel" <riel@xxxxxxxxxx>
Subject: RE: [Xen-devel] x86-64 machine_to_phys vs NX bit
From: "Ian Pratt" <m+Ian.Pratt@xxxxxxxxxxxx>
Date: Fri, 25 Aug 2006 16:56:48 +0100
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Thread-index: AcbIWupKKQk+BDROEdut6gAKle7CWAAAGfAAAADhVrA=
Thread-topic: [Xen-devel] x86-64 machine_to_phys vs NX bit
> > No, it gets shifted right 12 and *then* converted to a long. So you
> > get a 44-bit addressing capability (32+12). But NX bit is bit 63, so
> > it gets truncated.
> 
> Yes. For (on-going) 32-bit PV guests running on the 64-bit Xen, I
guess
> we should fix the convenient optimization now?

Or we restrict 32b guests to the bottom 16 terabytes of memory. Please
send me a machine for testing the patch :-)

Ian

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