I'm trying to get VGA passthrough working on VirtualBox with a Windows guest. Per the VirtualBox manual:
Limitations:
1. Only PCI cards with non-shared interrupts (such as using MSI on host) are supported at the moment.
How do I determine whether my secondary PCI video card has shared interrupts? I see nothing obvious in /proc/interrupts... but possibly that's because I already have my secondary card associated with pci-stub.
You can determine the interrupts in use on your system with lsdev which is part of the procinfo package.
It can be installed with the command sudo apt-get install procinfo
Once installed you can issue the command 'lsdev'
You should get output similar to this:
$ lsdev
Device DMA IRQ I/O Ports
------------------------------------------------
0000:00:02.0 f000-f03f
0000:00:1f.2 f060-f07f f080-f083 f090-f097 f0a0-f0a3 f0b0-f0b7
0000:00:1f.3 f040-f05f
0000:02:00.0 e000-e07f
acpi 9
ACPI 0400-0403 0404-0405 0408-040b 0410-0415 0420-042f 0450-0450
ahci 41 f060-f07f f080-f083 f090-f097 f0a0-f0a3 f0b0-f0b7
atl1c e000-e07f
cascade 4
dma 0080-008f
dma1 0000-001f
dma2 00c0-00df
ehci_hcd:usb1 16
ehci_hcd:usb2 23
eth0 45
fpu 00f0-00ff
i8042 1 12
i915 43
it87 0a35-0a36 0a35-0a36
iTCO_wdt 0430-0433 0460-047f
keyboard 0060-0060 0064-0064
mei_me 42
PCI 0000-0cf7 0cf8-0cff 0d00-ffff e000-efff
pic1 0020-0021
pic2 00a0-00a1
pnp 0200-020f 0454-0457 0458-047f 04d0-04d1 0500-057f 0680-069f 0a00-0a0f 0a20-0a2f 0a30-0a3f 164e-164f ffff-ffff ffff-ffff
rtc0 8 0070-0077
snd_hda_intel 44
timer 0
timer0 0040-0043
timer1 0050-0053
vesafb 03c0-03df
xhci_hcd 40
As you can see the IRQ's in use are listed in the IRQ column. By reviewing this information you can determine whether you have devices sharing an IRQ (interrupt).
