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-ia64-devel

Re: [Xen-ia64-devel] [PATCH] add volatile to pte entry of the p2m table

To: Alex Williamson <alex.williamson@xxxxxx>
Subject: Re: [Xen-ia64-devel] [PATCH] add volatile to pte entry of the p2m table
From: Isaku Yamahata <yamahata@xxxxxxxxxxxxx>
Date: Sat, 10 Jun 2006 11:50:07 +0900
Cc: xen-ia64-devel@xxxxxxxxxxxxxxxxxxx
Delivery-date: Fri, 09 Jun 2006 19:50:19 -0700
Envelope-to: www-data@xxxxxxxxxxxxxxxxxx
In-reply-to: <1149872812.5523.22.camel@lappy>
List-help: <mailto:xen-ia64-devel-request@lists.xensource.com?subject=help>
List-id: Discussion of the ia64 port of Xen <xen-ia64-devel.lists.xensource.com>
List-post: <mailto:xen-ia64-devel@lists.xensource.com>
List-subscribe: <http://lists.xensource.com/cgi-bin/mailman/listinfo/xen-ia64-devel>, <mailto:xen-ia64-devel-request@lists.xensource.com?subject=subscribe>
List-unsubscribe: <http://lists.xensource.com/cgi-bin/mailman/listinfo/xen-ia64-devel>, <mailto:xen-ia64-devel-request@lists.xensource.com?subject=unsubscribe>
References: <20060609091606.GH14764%yamahata@xxxxxxxxxxxxx> <1149872812.5523.22.camel@lappy>
Sender: xen-ia64-devel-bounces@xxxxxxxxxxxxxxxxxxx
User-agent: Mutt/1.4.2.1i
Hi Alex.

On Fri, Jun 09, 2006 at 11:06:52AM -0600, Alex Williamson wrote:
> On Fri, 2006-06-09 at 18:16 +0900, Isaku Yamahata wrote:
> > add volatile to pte entry of the p2m table.
> > p2m table are shared by cpu. added volatile as compiler barrier.
> 
>    Are all of these really needed?  Seems a little overkill to me.

Actually no.
assign_new_domain_page() and its families and domain_page_mapped()
are used only when domain construction (for now).
So their pte accesses aren't racy.

However, to remove volatile of them, non-volatile version
of lookup_alloc_domain_pte() is needed.
Because domain creation isn't performance critical,
I did't think it was worthwhile to both volatile version
and non-volatile version of lookup_alloc_domain_pte().

Scattering volatile is very ugly and I don't have any reason 
to stick to add volatile to assing_new_domain_page() and its variants.
If you prefer, I'll remove volatile of them.

-- 
yamahata

_______________________________________________
Xen-ia64-devel mailing list
Xen-ia64-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-ia64-devel