Re: [dpdk-dev] Having troubles binding an SR-IOV VF to uio_pci_generic on Amazon instance

["Michael S. Tsirkin" <mst@redhat.com>]

On Sun, Sep 27, 2015 at 10:05:11AM +0300, Vlad Zolotarov wrote:
> 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

This is expected. uio_pci_generic forwards INT#x interrupts from device
to userspace, but VF devices never assert INT#x.

So it doesn't seem to make any sense to bind uio_pci_generic there.

I think that DPDK should be fixed to not require uio_pci_generic
for VF devices (or any devices without INT#x).

If DPDK requires a place-holder driver, the pci-stub driver should
do this adequately. See ./drivers/pci/pci-stub.c

-- 
MST