IRQ issue on graphics card passthrough

["André Weidemann" <Andre.Weidemann@web.de>]

Hi,
as mentioned before I have successfully passed a graphics card from a 
Linux host to VM using qemu-kvm.

Shortly after starting the VM and before Windows7 initializes the 
graphics card, "info pci" looks like this:
   Bus  0, device   4, function 0:
     VGA controller: PCI device 1002:6719
       IRQ 10.
       BAR0: 32 bit prefetchable memory at 0xe0000000 [0xefffffff].
       BAR2: 32 bit memory at 0xfeba0000 [0xfebbffff].
       BAR4: I/O at 0xc000 [0xc0ff].
       BAR6: 32 bit memory at 0xffffffffffffffff [0x0001fffe].
       id "radeon6950"

After Windows has initialized the graphics card, "info pci" lists the 
following for the graphics card:
   Bus  0, device  4, function 0:
     VGA controller: PCI device 1002:6719
       IRQ 0.
       BAR0: 32 bit prefetchable memory at 0xe0000000 [0xefffffff].
       BAR2: 32 bit memory at 0xfeba0000 [0xfebbffff].
       BAR4: I/O at 0xc000 [0xc0ff].
       BAR6: 32 bit memory at 0xffffffffffffffff [0x0001fffe].
       id "radeon6950"

Notice that the IRQ changed from 10 to 0...

The graphics card's IRQ under Windows7 is displayed as:
"0xFFFFFFFE (-2)".

During another problem of assigning sound cards to a  VM, Jan Kiszka has 
pointed me to a patch that addresses an IRQ issue: 
http://thread.gmane.org/gmane.comp.emulators.qemu/102540
Unfortuantely it does not help here.

What can I do to examine this issue further?

Regards
  André