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

To:	"Ian Pratt" <m+Ian.Pratt@xxxxxxxxxxxx>, "Keir Fraser" <Keir.Fraser@xxxxxxxxxxxx>, "Rik van Riel" <riel@xxxxxxxxxx>
Subject:	RE: [Xen-devel] x86-64 machine_to_phys vs NX bit
From:	"Nakajima, Jun" <jun.nakajima@xxxxxxxxx>
Date:	Fri, 25 Aug 2006 10:02:10 -0700
Cc:	xen-devel@xxxxxxxxxxxxxxxxxxx
Delivery-date:	Fri, 25 Aug 2006 10:02:42 -0700
Envelope-to:	www-data@xxxxxxxxxxxxxxxxxx
List-help:	<mailto:xen-devel-request@lists.xensource.com?subject=help>
List-id:	Xen developer discussion <xen-devel.lists.xensource.com>
List-post:	<mailto:xen-devel@lists.xensource.com>
List-subscribe:	<http://lists.xensource.com/cgi-bin/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=subscribe>
List-unsubscribe:	<http://lists.xensource.com/cgi-bin/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=unsubscribe>
Sender:	xen-devel-bounces@xxxxxxxxxxxxxxxxxxx
Thread-index:	AcbIWupKKQk+BDROEdut6gAKle7CWAAAGfAAAADhVrAAAg1/YA==
Thread-topic:	[Xen-devel] x86-64 machine_to_phys vs NX bit

Ian Pratt wrote:
>>> 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
> 

No, we don't :-) It cannot happen on the architecture implementations
that exist today. Maybe ASSERT() would be sufficient so that it can
remind us of the issues in years.

Jun
---
Intel Open Source Technology Center

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel

WARNING - OLD ARCHIVES

xen-devel

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