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Re: [Xen-users] VGA passthrough radeon 4850 as primary card

On Feb 27,  1:14pm, povder wrote:
} Subject: [Xen-users] VGA passthrough radeon 4850 as primary card

> Hi all

Good morning, hope the weekend is going well for everyone.

I posted the availability of the following to xen-devel but have just
recently started to following xen-users as well.  Since there seemed
to be generic interest in this I thought it may be worthwhile to
re-post here.

> I'm trying to enable VGA passthrough in linux domU without
> success. I want to pass through AMD Radeon HD 4850 - 03:00.0 VGA
> compatible controller: Advanced Micro Devices [AMD] nee ATI RV770
> [Radeon HD 4850] as a _primary_ VGA for the VM. Nothing is showing
> up on the monitor that I have connected to graphics card's HDMI
> port. I have IOMMU enabled. I searched mailing lists and I don't
> know what to think about it. There is some information about ATI
> cards passthrough as primary VGA, some patches were posted but that
> was long time ago so my first question is:
> Is passthrough of ATI devices as primary VGA supposed to work now in
> Xen 4.2.1 without patches?

We have run thousands of sessions of primary VGA pass-through using
ATI cards.  We currently use stock Windows 7 with no additional

Patches are needed to QEMU in order to support primary pass-through.
The following URL references patches which will work for the 4.1.x and
4.2.x releases:



The patches can be applied and the updated qemu-dm can be dropped into
place, canonically in the /usr/lib/xen/bin directory.

The following is a sample configuration:
memory = 3072
name = "Windows"
viridian = 1
vif = [ 'type=ioemu, bridge=bridge0, model=e1000' ]
acpi = 1
apic = 1
disk = [ 'phy:/dev/localvg1/winsnap,hda,w' ]
pci=[ '01:00.0', '00:1a.0' ]

The BDF definitions for the pci pass-through directive are for the ATI
card and the USB host controller which drives the keyboard and mouse.

The trick to getting this right is to automate the detach and
re-attachment of the PCI devices to dom0.  The following script
provides a framework for doing this:


It should be salted according to the flavor of your particular
installation.  Access to the vbetool utility, which most distribution
include to support suspend/resume, is desirable in order to run the
BIOS-post initialization functions so the graphics card works properly
upon return of control to dom0.

You will want to have an SSH session open from an alternate location
to whatever platform you are testing this all on.  It will be the only
way to control the system if something goes awry during the
setup/teardown of the pass-through session.

Hope the above is helpful.

Have a good weekend.


}-- End of excerpt from povder

As always,
Dr. G.W. Wettstein, Ph.D.   Enjellic Systems Development, LLC.
4206 N. 19th Ave.           Specializing in information infra-structure
Fargo, ND  58102            development.
PH: 701-281-1686
FAX: 701-281-3949           EMAIL: greg@xxxxxxxxxxxx
"One uses power by grasping it lightly.  To grasp with too much force
 is to be taken over by power, thus becoming its victim."
                                -- Bene Gesserit Axiom

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