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][SVM] remove FFXSR CPUID bit for AMD-V HVM guests

To: "Jan Beulich" <jbeulich@xxxxxxxxxx>
Subject: RE: [Xen-devel] [PATCH][SVM] remove FFXSR CPUID bit for AMD-V HVM guests
From: "Woller, Thomas" <thomas.woller@xxxxxxx>
Date: Thu, 1 Feb 2007 08:58:23 -0600
Cc: xen-devel@xxxxxxxxxxxxxxxxxxx
Delivery-date: Thu, 01 Feb 2007 06:58:19 -0800
Envelope-to: www-data@xxxxxxxxxxxxxxxxxx
In-reply-to: <45C1B0CB.76E4.0078.0@xxxxxxxxxx>
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: AcdF2Zpt0kIFo1hYQqqm12rANySlcgANpi+Q
Thread-topic: [Xen-devel] [PATCH][SVM] remove FFXSR CPUID bit for AMD-V HVM guests
> >>> "Woller, Thomas" <thomas.woller@xxxxxxx> 01.02.07 00:06 >>>
> >Remove visibility of the FFXSR CPUID bit to an HVM guest.
> >This patch allows HVM Windows x64 to install/boot on AMD-V platforms.
> 
> Would you mind explaining why this is necessary? (Similarly I 
> have a hard time understanding why 3dnow can't be allowed for 
> hvm guests.)
There is no known issue with FFSRX at this time, an alternative (that
works) is to modify the code in long_mode_do_msr_write() to not gp fault
on FFSRX bit being set (this was the original failure).  

        if ( msr_content & ~(EFER_FFSRX | EFER_LME | EFER_LMA | EFER_NX
| EFER_SCE) )
        {
            gdprintk(XENLOG_WARNING, "Trying to set reserved bit in "
                     "EFER: %"PRIx64"\n", msr_content);
            goto gp_fault;
        }

The above code also allows windows to continue installation and function
seemingly properly.

So, to answer your Q, there is not a particular known failure case for
3DNow! Or FFSRX disablement - the issue would be that there has been no
directed testing effort concerning 3DNow and FFSRX usages in the guest
to determine if would be any issues per se.  

tom



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