Re: [dpdk-dev] [PATCH v4] net/ice: add flow mark hint support

[Thomas Monjalon <thomas@monjalon.net>]

21/11/2019 02:19, Zhang, Qi Z:
> From: Thomas Monjalon <thomas@monjalon.net>
> > 19/11/2019 07:14, Qi Zhang:
> > > Since not all data paths support flow mark, the driver needs a hint
> > > from application to select the correct data path if flow mark is
> > > required. The patch introduces a devarg "flow-mark-support" as a
> > > workaround solution, since a standard way is still ongoing.
> > >
> > > Signed-off-by: Qi Zhang <qi.z.zhang@intel.com>
> > > Acked-by: Qiming Yang <qiming.yang@intel.com>
> > > ---
> > > +- ``Flow Mark Support`` (default ``0``)
> > > +
> > > +  This is a hint to the driver to select the data path that supports
> > > + flow mark extraction  by default.
> > > +  NOTE: This is an experimental devarg, it will be removed when any
> > > + of below conditions  is ready.
> > > +  1) all data paths support flow mark (currently vPMD does not)
> > > +  2) a new offload like RTE_DEV_RX_OFFLOAD_FLOW_MARK be introduced
> > as a standard way to hint.
> > 
> > When the data path is selected?
> 
> dev_start
> 
> > I suppose such decision should be done when starting the port, after everything
> > is configured.
> > So you can check if a rte_flow rule was added for mark action.
> > Why the user needs to use an explicit option?
> 
> A rte_flow with mark can be issued at any time after dev_start when it is need, in that case, we have to reject the flow, this has been complained a lot base on previous feedback by users, since inconsistent behavior (sometimes mark works, some time it does not) is not expected

OK so you confirm the problem is only when a configuration
is changed at runtime without stopping the port.

> Also this option is overwhelmed by option 1 if we plan to do a clean fix in driver.

You want the application (or the user) to announce in advance which
configuration could be applied during the runtime.
I think we should consider the problem for any runtime configuration.
We never clearly defined which configuration is allowed at runtime.

Which other configs may be setup at runtime? MTU? VLAN? mirroring?
tunneling checksum? promiscuous? supported packet types? IEEE1588?