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] [PATCH] Allow PV superpages to work with live migration

To: Tim Deegan <Tim.Deegan@xxxxxxxxxx>
Subject: Re: [Xen-devel] [PATCH] Allow PV superpages to work with live migration
From: Dave McCracken <dcm@xxxxxxxx>
Date: Tue, 18 May 2010 11:21:12 -0500
Cc: Jeremy Fitzhardinge <jeremy@xxxxxxxx>, Xen Developers List <xen-devel@xxxxxxxxxxxxxxxxxxx>, Keir Fraser <Keir.Fraser@xxxxxxxxxxxxx>
Delivery-date: Tue, 18 May 2010 09:22:15 -0700
Envelope-to: www-data@xxxxxxxxxxxxxxxxxxx
In-reply-to: <20100518143205.GH4164@xxxxxxxxxxxxxxxxxxxxxxx>
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: <201005171410.47235.dcm@xxxxxxxx> <201005180920.18349.dcm@xxxxxxxx> <20100518143205.GH4164@xxxxxxxxxxxxxxxxxxxxxxx>
Sender: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx
User-agent: KMail/1.13.3 (Linux/2.6.32; KDE/4.4.3; x86_64; ; )
On Tuesday, May 18, 2010, Tim Deegan wrote:
> At 15:20 +0100 on 18 May (1274196018), Dave McCracken wrote:
> > I'm confused.  As far as I know, opt_allow_hugeage only affects PV
> > guests.  All I did in the macro was add a test for it.  I didn't touch
> > any of the HVM logic.  Are you saying the HVM logic is wrong or that
> > opt_allow_hugepage affects HVM guests in some fashion?
> 
> It would affect them after your change:
> 
> +    return (opt_allow_hugepage ||
> +           (is_hvm_vcpu(v) &&
> +            (GUEST_PAGING_LEVELS != 2
> +             || !hvm_paging_enabled(v)
> +             || (v->arch.hvm_vcpu.guest_cr[4] & X86_CR4_PSE))));
> 
> This makes the whole predicate true _even_for_hvm_guests_ whenever
> opt_allow_hugepage is true.  It should not be true for HVM guests that
> have disabled PSE, regardless of the setting of opt_allow_hugepage.

Ahh, right.  It didn't occur to me that people might set that parameter on 
machines with HVM guests.  I suppose it would be reasonable if they had a mix 
of PV and HVM on the same machine.

On Tuesday, May 18, 2010, Keir wrote:
> I already fixed this when I applied the patch this morning.

Thanks.

Dave

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