Re: Help Running Example

[Stephen Hemminger <stephen@networkplumber.org>]

On Sun, 6 Aug 2023 11:33:43 -0400
Alan Beadle <ab.beadle@gmail.com> wrote:

> Hi,
> 
> I need some help getting DPDK working. I am running Ubuntu 20.04 with
> a modified Linux 5.4 kernel, but I have also tried the stock Ubuntu
> 5.15 kernel with the same results.
> 
> Here is my NIC info from lspci:
> 00:1f.6 Ethernet controller: Intel Corporation Ethernet Connection (3)
> I219-LM (rev 09)
> 
> I built and installed DPDK from source, and applied the following boot
> flags: "intel_iommu=on iommu=pt"
> 
> After booting I did the following as root:
> echo 1024 > /sys/kernel/mm/hugepages/hugepages-2048kB/nr_hugepages
> ifconfig enp0s31f6 down
> dpdk-devbind.py --bind=vfio-pci 0000:00:1f.6
> 
> All of this appeared to work.
> 
> I tried running the "skeleton" example program and got the following output:
> sudo ./build/basicfwd
> EAL: Detected CPU lcores: 16
> EAL: Detected NUMA nodes: 1
> EAL: Detected shared linkage of DPDK
> EAL: Multi-process socket /var/run/dpdk/rte/mp_socket
> EAL: Selected IOVA mode 'VA'
> EAL: VFIO support initialized
> EAL: 0000:00:1f.6 VFIO group is not viable! Not all devices in IOMMU
> group bound to VFIO or unbound
> EAL: Requested device 0000:00:1f.6 cannot be used
> TELEMETRY: No legacy callbacks, legacy socket not created
> EAL: Error - exiting with code: 1
>   Cause: Error: number of ports must be even
> 
> I'm not at all familiar with DPDK or VFIO. What might the problem be?
> 
> -Alan

IOMMU groups are when multiple PCI devices share the same channel
in the IOMMU. The group is used to determine what mapping to use when
device does DMA. Since this is a security thing, devices in same IOMMU
group can not be shared between kernel and non-kernel usage.

The IOMMU group is determined by wiring on the motherboard.
Usually it is things like multiple Ethernet ports sharing the same group.
But can be much more confused.

The only option is to unbind all devices in the group before using
one with DPDK.