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] reserved bit in ShadowPT

To: Wu Bingzheng <wubingzheng@xxxxxxx>
Subject: Re: [Xen-devel] reserved bit in ShadowPT
From: Tim Deegan <Tim.Deegan@xxxxxxxxxx>
Date: Tue, 1 Sep 2009 09:14:21 +0100
Cc: xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxx>
Delivery-date: Tue, 01 Sep 2009 01:14:47 -0700
Envelope-to: www-data@xxxxxxxxxxxxxxxxxxx
In-reply-to: <13451837.152251251775745912.JavaMail.coremail@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/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=subscribe>
List-unsubscribe: <http://lists.xensource.com/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=unsubscribe>
References: <13451837.152251251775745912.JavaMail.coremail@xxxxxxxxxxxxxxxxxx>
Sender: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx
User-agent: Mutt/1.5.17 (2007-11-01)
At 04:29 +0100 on 01 Sep (1251779345), Wu Bingzheng wrote:
> Hi,
> 
> Dose Shadow Page Table use reserved-bit (PFEC_reserved_bit) in Xen 3.3.0?

Yes.  It uses reserved bits in ptes to indicate entries that are known
to be either emulated-MMIO or not-present in the guest pagetables.  Then
in the fault handler it can use PFEC_reserved_bit to branch onto a fast
path for those cases without taking any locks or walking the guest
pagetables.

> In my test many page fault set reserved-bit. But I can't understand its 
> function, after reading SPT's page-fault handler.

Have a look at the definition of SH_L1E_MAGIC in arch/x86/mm/shadow/types.h

Cheers,

Tim.


-- 
Tim Deegan <Tim.Deegan@xxxxxxxxxx>
Principal Software Engineer, Citrix Systems (R&D) Ltd.
[Company #02300071, SL9 0DZ, UK.]

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

<Prev in Thread] Current Thread [Next in Thread>