Re: [dpdk-users] [ovs-dev] adding dpdk ports sharing same pci address to ovs-dpdk bridge

[Thomas Monjalon <thomas@monjalon.net>]

21/09/2017 10:04, Loftus, Ciara:
> > 20/09/2017 19:33, Kevin Traynor:
> > > On 09/08/2017 10:56 AM, Loftus, Ciara wrote:
> > > > It seems the DPDK function rte_eth_dev_get_port_by_name() will
> > > > always return the port ID of the first port on your NIC,
> > > > when you specify the single PCI address and that's where the
> > > > problem is. There doesn't seem to be a way currently to
> > > > indicate to the calling application that in fact two
> > > > (or more) port IDs are associated with the one PCI address.
> > 
> > We have two ports (with the same PCI address) so we should have
> > two different names.
> > Where the names passed to rte_eth_dev_get_port_by_name() come from?
> > It is the user parameter from options:dpdk-devargs=0002:01:00.0, right?
> 
> Yes, we're using the PCI address specified by the user in dpdk-devargs.
> 
> > > > I am cc-ing DPDK users mailing list for hopefully some input.
> > > > Are there any plans for the rte_eth_dev_get_port_by_name function
> > > > to be compatible with NICs with multiple ports under the same PCI address?
> > 
> > We cannot return two different ports for the same name.
> > There are two issues here:
> > 	- the input should not be the PCI address
> > 	- the ethdev function should look at ethdev name, not rte_device
> > one
> 
> This would require the user having to "guess" the DPDK ethdev name
> which is something we'd like to avoid.

Yes, but you can provide a way to list the ports with their names
and characteristics.

> We had the same problem using DPDK port IDs and decided not to use
> them anymore, and use the PCI instead as it took the guesswork out.
> Ethdev names and port IDs can change between tests, unlike the PCI
> address which tends to remain constant for a device.

We can add a requirement on ethdev names and make sure they remain
constant for a given port.

> > The idea is that we have only one rte_device object and we instantiate
> > two rte_eth_dev ports.
> > An ethdev port can be identified with its id (a number) or its unique name.
> > Unfortunately, the user cannot guess the port id or the name set by the
> > PMD.
> 
> Exactly. Thanks for clarifying what's going on under the hood.
> 
> Ciara
> 
> > 
> > > Hi Adrien/Nelio,
> > >
> > > Is this something you can answer? We're wondering how to handle this in
> > > OVS and whether a temporary or long term solution is needed.
> > 
> > I suggest to rely on ethdev name.
> > You will need to show to the user the mapping between the bus information
> > (PCI id here) and the device names.
> > 
> > Another alternative is to add a new function returning all ethdev ports
> > associated to a given rte_device resource.
> > So you would get two ports and you could pick one on the first "add-port",
> > and the other one for the second "add-port" command.
> > It means the user would be forced to add them in the right order if he
> > wants a reproducible result.