[dpdk-dev] Question on examples/multi_process app

[Ananyev, Konstantin]

> -----Original Message-----
> From: Richardson, Bruce
> Sent: Wednesday, March 23, 2016 11:45 AM
> To: Ananyev, Konstantin
> Cc: Harish Patil; dev at dpdk.org
> Subject: Re: [dpdk-dev] Question on examples/multi_process app
> 
> On Wed, Mar 23, 2016 at 11:09:17AM +0000, Ananyev, Konstantin wrote:
> > Hi everyone,
> >
> > > -----Original Message-----
> > > From: dev [mailto:dev-bounces at dpdk.org] On Behalf Of Bruce Richardson
> > > Sent: Tuesday, March 22, 2016 9:38 PM
> > > To: Harish Patil
> > > Cc: dev at 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,

Not sure how?
All this replay is done at rte_ethdev layer.
Honestly, so far I don't remember any complaint about promisc on/off.

> and conflicts slightly with
> what is stated in the docs.

Update the docs? :)

> 
> /Bruce