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

[Xen-devel] Re: [PATCH] libxc: remove CPUID core information mangling

To: Andre Przywara <andre.przywara@xxxxxxx>, Nitin Kamble <nitin.a.kamble@xxxxxxxxx>
Subject: [Xen-devel] Re: [PATCH] libxc: remove CPUID core information mangling
From: Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
Date: Wed, 25 Aug 2010 13:42:17 +0100
Cc: xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxx>
Delivery-date: Wed, 25 Aug 2010 05:43:17 -0700
Envelope-to: www-data@xxxxxxxxxxxxxxxxxxx
In-reply-to: <4C7506BA.4000001@xxxxxxx>
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>
Sender: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx
Thread-index: ActETlIeKSQ6fVmrTR+qm3z+KJqzSgABKEv2
Thread-topic: [PATCH] libxc: remove CPUID core information mangling
User-agent: Microsoft-Entourage/12.26.0.100708
On 25/08/2010 13:04, "Andre Przywara" <andre.przywara@xxxxxxx> wrote:

> Hi,
> 
> c/s 18560:782599274bf9ae8857c55856c9c7fdf082967808 introduced CPUID
> mangling resulting in a doubled number of cores/processor exposed to the
> guest. According to comments in this patch the rationale behind this is
> to match the APIC numbering used by Xen.
> In my understanding the CPUID leafs dealing with number of cores always
> talk about logical numbers and not APIC IDs. So we don't need to adjust
> the CPUID readout to match the APIC ID enumeration scheme.
> If there were any serious reasons resulting in the old patch I'd love to
> hear them.
> 
> The attached patch fixes this and solves an issue I saw with certain
> NUMA guest configurations.

I think you shouldn't change handling of 80000008:ECX[15:12] since that does
explicitly refer to APIC ID arrangement. The rest of your changes could be
correct as far as I can tell from the reference manuals.

The intent by the way was to pass through host cores-per-package info so
that software licenses based on #packages would operate correctly in a
virtualised environment. It's pretty hacky though indeed.

 -- Keir

> Signed-off-by: Andre Przywara <andre.przywara@xxxxxxx>



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