From: Thomas Monjalon <thomas@monjalon.net>
To: Ferruh Yigit <ferruh.yigit@intel.com>
Cc: Hyong Youb Kim <hyonkim@cisco.com>,
"John Daley (johndale)" <johndale@cisco.com>,
Andrew Rybchenko <arybchenko@solarflare.com>,
Qi Zhang <qi.z.zhang@intel.com>, "dev@dpdk.org" <dev@dpdk.org>,
Shahaf Shuler <shahafs@mellanox.com>,
Jerin Jacob <jerin.jacob@caviumnetworks.com>,
David Marchand <david.marchand@6wind.com>,
Maxime Coquelin <maxime.coquelin@redhat.com>,
Konstantin Ananyev <konstantin.ananyev@intel.com>,
Hemant Agrawal <hemant.agrawal@nxp.com>,
Stephen Hemminger <stephen@networkplumber.org>,
gaetan.rivet@6wind.com
Subject: Re: [dpdk-dev] [PATCH v2] net/enic: add private API to set ingress VLAN rewrite mode
Date: Tue, 19 Mar 2019 21:30:53 +0100 [thread overview]
Message-ID: <3429576.gmczXWLcQl@xps> (raw)
Message-ID: <20190319203053.wbOIS4Prbddl-gqIhC9q6kEWDWhSNzIse0ppwKInL2A@z> (raw)
In-Reply-To: <dd783b94-bb54-b8c3-aed6-3f28238282a1@intel.com>
19/03/2019 19:00, Ferruh Yigit:
> On 3/19/2019 5:36 PM, Thomas Monjalon wrote:
> > 19/03/2019 18:29, Ferruh Yigit:
> >> On 3/14/2019 10:04 PM, Thomas Monjalon wrote:
> >>> 14/03/2019 03:58, Hyong Youb Kim:
> >>>> On Wed, Mar 13, 2019 at 10:29:53PM +0100, Thomas Monjalon wrote:
> >>>>> 13/03/2019 22:11, John Daley (johndale):
> >>>>>> From: Thomas Monjalon <thomas@monjalon.net>
> >>>>>>> 13/03/2019 19:32, Ferruh Yigit:
> >>>>>>>> On 3/5/2019 7:11 AM, Hyong Youb Kim wrote:
> >>>>>>>>> The driver currently has a devarg to set the rewrite mode during
> >>>>>>>>> init. Some apps want to programatically set it after running
> >>>>>>>>> rte_eal_init() and finding that ports are VIC. Add a private
> >>>>>>>>> function to support such applications.
> >>>>>>>>
> >>>>>>>> It is not good idea to have PMD specific APIs (although we already have
> >>>>>>> some).
> >>>>>>>>
> >>>>>>>> Specific to this case, as far as I can see it is to pass a config
> >>>>>>>> value and do the action related to it, what would you think having a
> >>>>>>>> generic key/value set/get API in ethdev for this? Similar to rawdev
> >>>>>>> get_attr/set_attr [1]?
> >>>>>>>>
> >>>>>>>> My concern is it may turn into something like ioctl with many things
> >>>>>>>> pushed to it, and cause possible duplication ...
> >>>>>>>
> >>>>>>> Yes, it is clearly ioctl style.
> >>>>>>>
> >>>>>>> Please could you explain more what is the rewrite mode?
> >>>>>>> Does it apply to the port or the queue?
> >>>>>>>
> >>>>>> It applies to a port. By default the Cisco VIC VLAN tags every packet on ingress even if they were untagged coming in on the wire. They are tagged with VLAN 0 or a VLAN id programmed into the NIC depending on the configuration. Its part of the original design, to maintain priority bits, ancient history.
> >>>>>>
> >>>>>> Some apps don't like this (VPP) or take a slower path (OVS). Hyong added a ig-vlan-rewrite=untag devarg to disable this (leave untagged/default vlan packets untagged) during rte_eal_init and this is helpful for OVS, but VPP likes to set the rewrite mode after rte_eal_init() and finding the ports are VIC ports. So that is the reasoning behind the private API call.
> >>>>>
> >>>>> It looks like an application will always set this flag or never.
> >>>>> So I don't see the need for an API function.
> >>>>> Why VPP prefers set this flag later?
> >>>>> Would it be better to have some driver-specific flags, no matter the ports?
> >>>>
> >>>> As is, there seem to be two ways apps deal with NIC-specific tweaks/quirks.
> >>>>
> >>>> 1. Leave everything to the user.
> >>>>
> >>>> Let the human user specify NIC-specific settings (e.g. devarg,
> >>>> not-so-standard MTU/MRU, offloads with not-so-uniform behavior). The
> >>>> app simply passes these to DPDK and does nothing else. Devargs are
> >>>> passed to rte_eal_init. Other settings are applied during the
> >>>> configure phase after rte_eal_init.
> >>>>
> >>>> For example, OVS seems to go for a smallest common denominator that
> >>>> works with most NICs out of the box. Otherwiese, it kinda falls into
> >>>> this camp.
> >>>>
> >>>> For a problematic NIC that needs user intervention, troubleshooting
> >>>> goes like this :-)
> >>>> - Install app.
> >>>> - Run with settings that worked on a previous machine.
> >>>> - Some features suddenly do not work.
> >>>> - Google search this and that ("why this does not work on this server?").
> >>>> - Contact vendors.
> >>>> - Find out this NIC has unexpected behavior.
> >>>> - Set devarg, tweak MTU/MRU, ... ("Oh need to set this for ..").
> >>>> - Now the features work.
> >>>>
> >>>> 2. Hide ugly tweaks from the user.
> >>>>
> >>>> VPP falls into this camp. The user specifies BDFs in the config (no
> >>>> devargs). The app calls rte_eal_init(BDFs), iterates through the
> >>>> discovered ports, applies whatever NIC-specific settings necessary
> >>>> during the configure phase (i.e. do this for vendor A NIC, do that for
> >>>> vendor B NIC), and then start the ports.
> >>>>
> >>>> The ingress vlan rewrite mode is devarg now, so is not usable in this
> >>>> model. One way around it is a private API. Driver specific flags
> >>>> during the configure phase would also work fine. Though, enic might be
> >>>> the only user of those flags.
> >>>
> >>> I think DPDK needs some driver configuration.
> >>> Currently the config is done per device with devargs.
> >>> The next devargs format allow this:
> >>> driver=enic,rewrite=on
> >>> and it can be passed to rte_eal_init().
> >>>
> >>> We did not progress on the implementation of this format in recent months,
> >>> but you are welcome to help!
> >>> Instead of passing devargs in the whitelist/blacklist options,
> >>> we should introduce a new option, like --dev.
> >>
> >> But it will be still devarg in new implementation.
> >
> > With the new syntax, no need to specify a device.
> > We can match a driver or multiple drivers sharing the same property.
> >
> >> I guess for this use case, there is a need to pass this information from an API.
> >> Options can be:
> >> 1- PMD specific API
> >> 2- Extend ethdev dev_ops for each usecase
> >> 3- Have a generic API, as suggested above
> >> 4- Extend configure to accept flags
> >>
> >> I don't see a winner in above list, each has some problems. Any comment on how
> >> to proceed?
> >
> > I don't see a problem with the devargs approach.
>
> Devargs either passed via command line to DPDK application, or parameter to
> hotplug APIs.
The application can pass whatever it wants to EAL.
In the case described above, the application wants to enable
a mode of the driver for all its devices.
That's why I think the right solution is a driver option,
which can be achieved with the new devargs syntax.
> If someone wants to use regular probe without any command line argument, and
> later configure the device via an API, can devargs be used?
This is a scenario different of what is asked above.
In the case of a specific configuration of one device,
we have three choices.
These are your suggestions, with my comments:
1- PMD specific API
2- Extend ethdev dev_ops for each usecase
(3- Have a generic API) = choice 2
(4- Extend configure to accept flags) = choice 1
This is a choice 3:
- no support of exotic features
next prev parent reply other threads:[~2019-03-19 20:31 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-05 5:56 [dpdk-dev] [PATCH] " Hyong Youb Kim
2019-03-05 7:11 ` [dpdk-dev] [PATCH v2] " Hyong Youb Kim
2019-03-13 18:32 ` Ferruh Yigit
2019-03-13 20:36 ` Thomas Monjalon
2019-03-13 20:36 ` Thomas Monjalon
2019-03-13 21:11 ` John Daley (johndale)
2019-03-13 21:11 ` John Daley (johndale)
2019-03-13 21:29 ` Thomas Monjalon
2019-03-13 21:29 ` Thomas Monjalon
2019-03-14 2:58 ` Hyong Youb Kim
2019-03-14 2:58 ` Hyong Youb Kim
2019-03-14 22:04 ` Thomas Monjalon
2019-03-14 22:04 ` Thomas Monjalon
2019-03-19 17:29 ` Ferruh Yigit
2019-03-19 17:29 ` Ferruh Yigit
2019-03-19 17:36 ` Thomas Monjalon
2019-03-19 17:36 ` Thomas Monjalon
2019-03-19 18:00 ` Ferruh Yigit
2019-03-19 18:00 ` Ferruh Yigit
2019-03-19 20:30 ` Thomas Monjalon [this message]
2019-03-19 20:30 ` Thomas Monjalon
2019-03-20 10:45 ` Ferruh Yigit
2019-03-20 10:45 ` Ferruh Yigit
2019-03-20 11:46 ` Thomas Monjalon
2019-03-20 11:46 ` Thomas Monjalon
2019-03-25 11:49 ` Ferruh Yigit
2019-03-25 11:49 ` Ferruh Yigit
2019-03-25 13:26 ` Gaëtan Rivet
2019-03-25 13:26 ` Gaëtan Rivet
2019-03-25 13:33 ` Gaëtan Rivet
2019-03-25 13:33 ` Gaëtan Rivet
2019-03-26 6:39 ` Hyong Youb Kim
2019-03-26 6:39 ` Hyong Youb Kim
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