WARNING - OLD ARCHIVES

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/
   
 
 
Xen 
 
Home Products Support Community News
 
   
 

xen-devel

Re: [Xen-devel] PV guest + shadow paging

To: Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>
Subject: Re: [Xen-devel] PV guest + shadow paging
From: Jeremy Fitzhardinge <jeremy@xxxxxxxx>
Date: Wed, 24 Oct 2007 11:59:07 -0700
Cc: Tim Deegan <Tim.Deegan@xxxxxxxxxxxxx>, Ian Pratt <Ian.Pratt@xxxxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxx, Levin Johnson <levin.johnson@xxxxxxxxx>, Ian Campbell <Ian.Campbell@xxxxxxxxxxxxx>
Delivery-date: Wed, 24 Oct 2007 12:00:00 -0700
Envelope-to: www-data@xxxxxxxxxxxxxxxxxx
In-reply-to: <C344D781.17557%Keir.Fraser@xxxxxxxxxxxx>
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: <C344D781.17557%Keir.Fraser@xxxxxxxxxxxx>
Sender: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx
User-agent: Thunderbird 2.0.0.5 (X11/20070727)
Keir Fraser wrote:
> On 24/10/07 11:00, "Jeremy Fitzhardinge" <jeremy@xxxxxxxx> wrote:
>
>   
>> Tim Deegan wrote:
>>     
>>> The joy of NPT(VMI?)/EPT is that you don't need shadow pagetables at
>>> all. :)
>>>   
>>>       
>> Sure, but from a guest interface perspective they look the same.
>>     
>
> Would you want to take advantage of NPT/EPT once you've pv'ed your mmu
> interfaces?
>   

I think so.  NPT/EPT would seem to have all the advantages of shadow
paging and direct paging without the disadvantages.  We would avoid
taking faults/hypercalls on pagetable updates, and have the secondary
benefit of not needing to worry about page permissions on pagetables,
making it easier to use superpages for the kernel and in general. 
Perhaps the initial implementations will be sufficiently poor that it
isn't worth doing now, but I think it will in time.

    J

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