[ovs-dev] [patch net-next v2 8/9] switchdev: introduce Netlink API
Thomas Graf
tgraf at suug.ch
Sat Sep 20 11:51:40 UTC 2014
On 09/20/14 at 07:32am, Jamal Hadi Salim wrote:
> I am sorry to have tied the two together. Maybe not OVS but the approach
> described is heaven for vendor SDKs.
I fail to see the connection. You can use switch vendor SDK no matter
how we define the kernel APIs. They already exist and have been
designed in a way to be completely indepenedent from the kernel.
Are you referring to vendor specific decisions in user space in
general? I believe that the whole point of swdev is to provide *that*
level of abstraction so decisions can be made in a vendor neutral way.
> >The statement was that the requirement of deriving hardware flows from
> >software flows *in the kernel* is not flexible enough for the future
> >for reasons such as:
> >
> >1) The OVS software data path might be based on eBPF in the future and
> > it is unclear how we could derive hardware flows from that
> > transparently.
> >
>
> Who says you cant put BPF in hardware?
I don't think anybody is saying that. P4 is likely a reality soon. But
we definitely want hardware offload in a BPF world even if the hardware
can't do BPF yet.
> And why is OVS defining how BPF should evolve or how it should be used?
Not sure I understand. OVS would be a user of eBPF just like tracing,
xt_BPF, socket filter, ...
> >2) Depending on hardware capabilities. Hardware flows might need to be
> > assisted by software flow counterparts and it is believed that it
> > is the wrong approach to push all the necessary context for the
> > decision down into the kernel. This can be argued about and I don't
> > feel strongly either way.
> >
>
> Pointing to the current FDB offload: You can select to bypass
> and not use s/ware.
As I said, this can be argued about. It would require to push a lot of
context into the kernel though. The FDB offload is relatively trivial
in comparison to the complexity OVS user space can handle. I can't think
of any reasons why to complicate the kernel further with OVS specific
knowledge as long as we can guarantee the vendor abstraction.
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