This is an archived copy of the Xen.org mailing list, which we have preserved to ensure that existing links to archives are not broken. The live archive, which contains the latest emails, can be found at http://lists.xen.org/
Home Products Support Community News


Re: [Xen-devel] _domain in page_info structure

To: jeet <jeet_sat12@xxxxxxxxxxx>
Subject: Re: [Xen-devel] _domain in page_info structure
From: Tim Deegan <Tim.Deegan@xxxxxxxxxxxxx>
Date: Tue, 27 Mar 2007 08:37:31 +0000
Cc: xen-devel@xxxxxxxxxxxxxxxxxxx
Delivery-date: Tue, 27 Mar 2007 01:36:31 -0700
Envelope-to: www-data@xxxxxxxxxxxxxxxxxx
In-reply-to: <104213.18216.qm@xxxxxxxxxxxxxxxxxxxxxxxxx>
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>
References: <104213.18216.qm@xxxxxxxxxxxxxxxxxxxxxxxxx>
Sender: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx
User-agent: Mutt/1.5.13 (2006-08-11)
At 13:55 +0530 on 27 Mar (1175003752), jeet wrote:
> nd = page->u.inuse._domain;
> what this field is used for? 

The comment beside the definition of the field says:
/* Owner of this page (NULL if page is anonymous). */

> /* Meaning of the _domain field in shadow pages
>  * --------------------------------------------
>  *
>  * In shadow pages, this field will always have its least significant bit
>  * set.  This ensures that all attempts to get_page() will fail (as all
>  * valid pickled domain pointers have a zero for their least significant bit).
>  * Instead, the remaining upper bits are used to record the shadow generation
>  * counter when the shadow was created.
>  */

This comment is from 3.0.4 and was never very useful, as IIRC the
generation cuonters it refers to were never implemented in the main
tree.  Shadow pages have their own entirely separate version of the
page_info struct now.



Tim Deegan <Tim.Deegan@xxxxxxxxxxxxx>, XenSource UK Limited
Registered office c/o EC2Y 5EB, UK; company number 05334508

Xen-devel mailing list