Having troubles binding an SR-IOV VF to uio_pci_generic on Amazon instance

[Vlad Zolotarov <vladz@cloudius-systems.com>]

Hi,
I was trying to use uio_pci_generic with Intel's 10G SR-IOV devices on 
Amazon EC2 instances with Enhanced Networking enabled.
The idea is to create a DPDK environment that doesn't require compiling 
kernel modules (igb_uio).
However I was surprised to discover that uio_pci_generic refuses to work 
with EN device on AWS:

$ lspci
00:00.0 Host bridge: Intel Corporation 440FX - 82441FX PMC [Natoma] (rev 02)
00:01.0 ISA bridge: Intel Corporation 82371SB PIIX3 ISA [Natoma/Triton II]
00:01.1 IDE interface: Intel Corporation 82371SB PIIX3 IDE [Natoma/Triton II]
00:01.3 Bridge: Intel Corporation 82371AB/EB/MB PIIX4 ACPI (rev 01)
00:02.0 VGA compatible controller: Cirrus Logic GD 5446
00:03.0 Ethernet controller: Intel Corporation 82599 Ethernet Controller Virtual Function (rev 01)
00:04.0 Ethernet controller: Intel Corporation 82599 Ethernet Controller Virtual Function (rev 01)
00:1f.0 Unassigned class [ff80]: XenSource, Inc. Xen Platform Device (rev 01)

$ sudo ./dpdk/tools/dpdk_nic_bind.py -b uio_pci_generic 00:04.0
Error: bind failed for 0000:00:04.0 - Cannot bind to driver uio_pci_generic

$dmesg

--> snip <---
[  816.655575] uio_pci_generic 0000:00:04.0: No IRQ assigned to device: no support for interrupts?

$ sudo lspci -s 00:04.0 -vvv
00:04.0 Ethernet controller: Intel Corporation 82599 Ethernet Controller Virtual Function (rev 01)
	Physical Slot: 4
	Control: I/O- Mem+ BusMaster- SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx-
	Status: Cap+ 66MHz- UDF- FastB2B- ParErr- DEVSEL=fast >TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx-
	Region 0: Memory at f3008000 (64-bit, prefetchable) [size=16K]
	Region 3: Memory at f300c000 (64-bit, prefetchable) [size=16K]
	Capabilities: [70] MSI-X: Enable- Count=3 Masked-
		Vector table: BAR=3 offset=00000000
		PBA: BAR=3 offset=00002000
	Kernel modules: ixgbevf

So, as we may see the PCI device doesn't have an INTX interrupt line 
assigned indeed. It has an MSI-X capability however.
Looking at the uio_pci_generic code it seems to require the INTX:

uio_pci_generic.c: line 74: probe():

	if (!pdev->irq) {
		dev_warn(&pdev->dev, "No IRQ assigned to device: "
			 "no support for interrupts?\n");
		pci_disable_device(pdev);
		return -ENODEV;
	}

Is it a known limitation? Michael, could u, pls., comment on this?

thanks,
vlad