IRQ issue on graphics card passthrough

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.

Quoted 26 lines · André Weidemann

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"

Quoted 4 lines

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

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

That's not necessarily pointing to a problem, that just means Windows is using the device in MSI mode. Does it do the same when running natively?

Quoted 1 line

Quoted 4 lines

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.

For sure, that patch addresses a legacy interrupt issue, nothing MSI-related.