[Xen-users] Identifying graphics cards for passthrough

[Paul Stimpson <paul@xxxxxxxxxxxxxxxxxxxx>]

Hi,

I have an HP workstation here with two identical AMD V5900 graphics 
cards in it. I'm finding it really challenging following the 
instructions to get VGA passthrough working. Thanks for the help you've 
given me so far. The host OS is Ubuntu 12.04 LTS 64-bit with the XFCE 
desktop.
The Xen install has a Windows guest and I want to pass one of the cards 
through to it. The cards each appear as two devices (a graphics card and 
an associated sound card that provides the HDMI audio out). So I have:
    * 00:04:00.0 - Graphics card
    * 00:04:00.1 - Audio device
    * 00:05:00.0 - Graphics card
    * 00:05:00.1 - Audio device

I swapped which device was primary in the BIOS as it made the layout of 
the wiring on the back panel more logical.
My first stupid question is: How do I work out which card is the primary 
and secondary to know which one to pass into the guest please?
I think I need to use gfx_passthru=1

I am already passing other PCI devices through to the guest 
successfully. Say for example 00:06:00.0.
How do I write this for the conf file please. I tried things like:

    gfx_passthru=1
    pci=['0000:04:00.0','0000:04:00.1','0000:06:00.0']

and

    gfx_passthru=1
    pci=['0000:04:00.0']

    pci=['0000:04:00.1','0000:06:00.0']

I've had no success. Are these ways of writing it equivalent or do the 
PCI IDs need to be grouped in a specific way please?
I've seen some guides saying that I need to extract the contents of the 
EEPROM and bring it into the guest and some not mention it. Do I need to 
do this with an AMD card please?
I've also see reference to needing a copy of Xen after changeset 25070 
for graphics passthrough. I know I'm running Xen 4.2.0 as downloaded 
from the website but I don't still have the source code we compiled it 
from so I don't know if it's the right patch level. How can I work out 
if the copy I have is OK from an installed machine please?
Thanks,
Paul.


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