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 0/2] MTRR/PAT virtualization

To: Michael A Fetterman <Michael.Fetterman@xxxxxxxxxxxx>
Subject: Re: [Xen-devel] [PATCH 0/2] MTRR/PAT virtualization
From: Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>
Date: Tue, 09 Oct 2007 11:43:14 +0100
Cc: "Su, Disheng" <disheng.su@xxxxxxxxx>, "Dong, Eddie" <eddie.dong@xxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxx
Delivery-date: Tue, 09 Oct 2007 03:44:09 -0700
Envelope-to: www-data@xxxxxxxxxxxxxxxxxx
In-reply-to: <122c8cf10710090223h708523eckddaceb14205be2a2@xxxxxxxxxxxxxx>
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>
Sender: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx
Thread-index: AcgKYTGUcBIDLHZUEdy5aAAX8io7RQ==
Thread-topic: [Xen-devel] [PATCH 0/2] MTRR/PAT virtualization
User-agent: Microsoft-Entourage/11.3.6.070618
On 9/10/07 10:23, "Michael A Fetterman" <Michael.Fetterman@xxxxxxxxxxxx>
wrote:

>>> But, yes this is really a good point. So we need to do WBINVD when VP
>>> migrates (of course for pass-through domain only), while the prefered
>>> approach is to pin VCPU on pCPUs.
>> 
>> Or WBINVD all CPUs when a VCPU executes WBINVD. Or explicitly track dirty
>> caches for each vCPU.
> 
> I shutter to think of allowing a guest to cause a WBINVD.
> 
> In modern systems (8M+ of cache, etc), it can take 4+ milliseconds to execute.
> I dare say it could, in a worst case scenerio, be even worse if you
> did it on multiple
> CPUs or hyperthreads at once.  And the cpu is non-interruptable the entire
> time.

It only needs to be allowed for guests with direct hardware access. Those
WBINVD instructions in AGP drivers and the like are there for a reason, I
suspect.

 -- Keir



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