Re: [dpdk-dev] Question on examples/multi_process app

[Bruce Richardson <bruce.richardson@intel.com>]

On Wed, Mar 23, 2016 at 11:09:17AM +0000, Ananyev, Konstantin wrote:
> Hi everyone,
> 
> > -----Original Message-----
> > From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Bruce Richardson
> > Sent: Tuesday, March 22, 2016 9:38 PM
> > To: Harish Patil
> > Cc: dev@dpdk.org
> > Subject: Re: [dpdk-dev] Question on examples/multi_process app
> > 
> > On Tue, Mar 22, 2016 at 08:03:42PM +0000, Harish Patil wrote:
> > > Hi,
> > > I have a question regarding symmetric_mp and mp_server applications under
> > > examples/multi_process. In those apps, rte_eth_promiscuous_enable() is
> > > called before rte_eth_dev_start(). Is this the correct way to initialize
> > > the port/device? As per the description in
> > > http://dpdk.org/doc/api/rte__ethdev_8h.html:
> > >
> > > "The functions exported by the application Ethernet API to setup a device
> > > designated by its port identifier must be invoked in the following order:
> > >
> > > * rte_eth_dev_configure()
> > > * rte_eth_tx_queue_setup()
> > > * rte_eth_rx_queue_setup()
> > > * rte_eth_dev_start()
> > >
> > > Then, the network application can invoke, in any order, the functions
> > > exported by the Ethernet API to get the MAC address of a given device, to
> > > get the speed and the status of a device physical link, to
> > > receive/transmit [burst of] packets, and so on.”
> > >
> > > So should I consider this as an application issue or whether the PMD is
> > > expected to handle it? If PMD is to handle it, then should the PMD be:
> > >
> > > 1) Rejecting the Promisc config? OR
> > > 2) Cache the config and apply when dev_start() is called at later point?
> 
> Yes as I remember 2) is done.
> dev_start() invokes rte_eth_dev_config_restore(), which restores 
> promisc mode, mac addresses, etc.
> 
> > >
> > > Thanks,
> > > Harish
> > >
> > Good question. I think most/all of the Intel adapters, - for which the app was
> > originally written, way back in the day when there were only 2 PMDs in DPDK :)
> > - will handle the promiscuous mode call either before or after the dev start.
> > Assuming that's the case, and if it makes life easier for other driver writers,
> > we should indeed standardize on one supported way of doing things - the way
> > specified in the documentation being that one way, I would guess.
> > 
> > So, e1000, ixgbe maintainers - do you see any issues with forcing the promiscuous
> > mode set API to be called after the call to dev_start()?
> 
> Not sure, why do we need to enforce that restriction?
> Is there any problem with current way?

It complicates things for driver writers is all, and conflicts slightly with 
what is stated in the docs.

/Bruce