Re: [dpdk-dev] KNI discussion in userspace event

[Igor Ryzhov <iryzhov@nfware.com>]

On Fri, Oct 28, 2016 at 7:13 PM, Thomas Monjalon <thomas.monjalon@6wind.com>
wrote:

> 2016-10-28 15:51, Richardson, Bruce:
> > From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Thomas Monjalon
> > > 2016-10-28 15:31, Ferruh Yigit:
> > > > * virtio-user + vhost-net
> > > > This can be valid alternative, removes the out of tree kernel module
> > > > need. But missing control path. Proof of concept work will be done.
> > >
> > > That's probably a smart alternative for packet injection.
> > > What do you mean exactly by "missing control path"?
> >
> > We'll have to see how it performs - which is the key gap for data path
> that KNI fills. Until we get an alternative with (nearly) equivalent
> performance, there will be demand for KNI to stick around.
> > The "control path" is the ethtool part, to get stats and do operations
> on the NIC using command-line tools.
> >
> > >
> > > > * Remove ethtool support ?
> > >
> > > That's the other part of KNI.
> > > It works only for e1000/ixgbe. That's a niche.
> >
> > Yes, it's something we need to remove, but again, we need an alternative
> first.
> >
> > >
> > > > Still there is some interest, will keep it. But not able to extend it
> > > > to other drivers with current design.
> > >
> > > It should be removed one day.
> > > We must seriously think about a generic alternative.
> > > Either we add DPDK support in ethtool or we create a dpdk-ethtool.
> > > (or at least a library as the one in examples/).
> >
> > I don't view that as a great path forward. Sure, we can do our own
> ethtool, but then people will look for ifconfig to work, and "ip" to work,
> etc. I view having a kernel proxy module as the best path here as it is
> tool agnostic on the userspace side, rather than trying to make every tool
> for working with kernel netdevs also have support for dpdk ports.
>
> Yes that's the ultimately best solution.
> But:
> - we need some cooperation of the kernel team
> - ethtool manages a device (what DPDK provides) whereas iproute and others
> manage a TCP/IP stack so is out of control of DPDK.
>

That's not true.
iproute can control a lot of things like MAC address, promiscuous, MTU,
etc. that cannot be controlled with ethtool.
Just compare net_device_ops and ethtool_ops to see the difference.

And the question is not only about tools, it is also about how Linux kernel
works with network devices.
And it uses net_device_ops, not ethtool_ops.


>
> > > Or we do nothing and wait to have more hardware like Mellanox
> supporting a
> > > kernel bifurcated driver approach.
> >
> > Given the lack of other NICs supporting that, I think it could be quite
> a wait! Also, it doesn't work for virtio ports, for pcap ports, or any
> other ports which don't have physical hardware backing them. No reason you
> shouldn't be able to pull stats from all your dpdk ethdevs, not just the
> ones with physical hardware. The same ethdev APIs work for them, so should
> the same tools.
>
> Yes, very good point.
>
> > > > *KNI PMD
> > > > Patch is in the mail list, missing comments. If it gets some
> > > > interest/comments/acks it may go in to next release.
> > >
> > > I'm not against KNI PMD but it looks strange to add more support to an
> old
> > > dying approach.
> >
> > I think the main idea here is to clean up the API - at least for the
> data path. There is no reason why we need special KNI RX/TX functions, when
> ethdev RX/TX functions could do the job. However, at a higher level, the
> more basic requirement is that whatever solution for the data-path to
> kernel from dpdk is, it needs to appear as an ethdev, and not as a special
> library with different APIs, as KNI is now.
>
> Yes I agree to unifiy (and reduce) API.
> Why this PMD is not more commented?
> KNI users should be interested to review it.
> Please dear community, we need more reviews!
>