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RE: [Xen-users] Multiple VMs Using Multiple Video Cards w/Pacifica

To: "Steve Higton" <hpq8bfr.mailing.lists@xxxxxxxxxxxxx>, Xen-users@xxxxxxxxxxxxxxxxxxx
Subject: RE: [Xen-users] Multiple VMs Using Multiple Video Cards w/Pacifica
From: "Petersson, Mats" <Mats.Petersson@xxxxxxx>
Date: Wed, 3 May 2006 11:00:51 +0200
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Thread-topic: [Xen-users] Multiple VMs Using Multiple Video Cards w/Pacifica
> -----Original Message-----
> From: xen-users-bounces@xxxxxxxxxxxxxxxxxxx 
> [mailto:xen-users-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of 
> Steve Higton
> Sent: 02 May 2006 22:41
> To: Xen-users@xxxxxxxxxxxxxxxxxxx
> Subject: [Xen-users] Multiple VMs Using Multiple Video Cards 
> w/Pacifica
> Hi All,
> I've read a few references to the imminent AMD AM2 CPUs 
> including Pacifica technology and that these CPUs have an 
> io-mmu (I may have spelt that wrong or used incorrectly 
> terminology, if it's not an io-mmu it's something that allows 
> devices on the PCI/PCI-express bus to have their memory 
> remapped.) WIll this enable XenU domains to have access to 
> multiple video cards?  I would like to be able to have two 
> XenU domains have a PCI-express video card each to run two 
> independent displays in either Windows XP or Linux.

The short answer is: Probably not immediately.

Let's first sort out the naming of things: The code-name pacifica is now
called AMD Virtulization Technology or Secure Virtual Machine extension,
SVM for short. 

IOMMU is a technology that isn't implemented in the first generation SVM
processors, but will come in future processors [I don't honestly know at
which point in the future]. But yes, this technology will, amongst other
things, allow the mapping of virtualized "pseudo-physical" memory to
"real physical" memory. 

We do have an alternative, which is to use the GART for this. This has
been implemented in the x86-64 kernel for quite some time [to remap
IO-buffers from above 4GB to below 4GB so that 32-bit hardware can
access memory above 4GB], but so far there is no solution for Xen to use
this method, although I believe there is work in progress to make this. 

The second problem is that the PCI device hiding for Dom0 isn't
implemented for HVM systems. I think this is also being worked on (or at
least it's on someones list to be done when they get to that item on the
list or something like that). 


> Thanks,
> Steve.
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