Re: [dpdk-dev] [PATCH v3 1/5] ethdev: add API to negotiate delivery of Rx meta data

[Ori Kam <orika@nvidia.com>]

Hi Ivan,

> -----Original Message-----
> From: Ivan Malov <Ivan.Malov@oktetlabs.ru>
> Sent: Sunday, October 3, 2021 12:30 PM
> data
> 
> Hi Ori,
> 
> Thanks for reviewing this.
> 

No problem.

> On 03/10/2021 10:42, Ori Kam wrote:
> > Hi Andrew and Ivan,
> >
> >
> >> -----Original Message-----
> >> From: Andrew Rybchenko <andrew.rybchenko@oktetlabs.ru>
> >> Sent: Friday, October 1, 2021 9:50 AM
> >> Subject: Re: [PATCH v3 1/5] ethdev: add API to negotiate delivery of
> >> Rx meta data
> >>
> >> On 9/30/21 10:07 PM, Ivan Malov wrote:
> >>> Hi Ori,
> >>>
> >>> On 30/09/2021 17:59, Ori Kam wrote:
> >>>> Hi Ivan,
> >>>> Sorry for jumping in late.
> >>>
> >>> No worries. That's OK.
> >>>
> >>>> I have a concern that this patch breaks other PMDs.
> >>>
> >>> It does no such thing.
> >>>
> >>>>>  From the rst file " One should negotiate flag delivery beforehand"
> >>>> since you only added this function for your PMD all other PMD will fail.
> >>>> I see that you added exception in the  examples, but it doesn't
> >>>> make sense that applications will also need to add this exception
> >>>> which is not documented.
> >>>
> >>> Say, you have an application, and you use it with some specific PMD.
> >>> Say, that PMD doesn't run into the problem as ours does. In other
> >>> words, the user can insert a flow with action MARK at any point and
> >>> get mark delivery working starting from that moment without any
> >>> problem. Say, this is exactly the way how it works for you at the
> moment.
> >>>
> >>> Now. This new API kicks in. We update the application to invoke it
> >>> as early as possible. But your PMD in question still doesn't support
> >>> this API. The comment in the patch says that if the method returns
> >>> ENOTSUP, the application should ignore that without batting an
> >>> eyelid. It should just keep on working as it did before the introduction of
> this API.
> >>>
> >
> > I understand that it is nice to write in the patch comment that
> > application should disregard this function in case of ENOTSUP but in a
> > few month someone will read the official doc, where it is stated that
> > this function call is a must and then what do you think the
> > application will do?
> > I think that the correct way is to add this function to all PMDs.
> > Another option is to add to the doc that if the function is returning
> > ENOTSUP the application should assume that all is supported.
> >
> > So from this point of view there is API break.
> 
> So, you mean an API breakage in some formal sense? If the doc is fixed in
> accordance with the second option you suggest, will it suffice to avoid this
> formal API breakage?
> 

Yes, but I think it will be better to add the missing function.

> >
> >>> More specific example:
> >>> Say, the application doesn't mind using either "RSS + MARK" or
> >>> tunnel offload. What it does right now is attempt to insert tunnel
> >>> flows first and, if this fails, fall back to "RSS + MARK". With this
> >>> API, the application will try to invoke this API with "USER_MARK |
> >>> TUNNEL_ID" in adapter initialised state. If the PMD says that it can
> >>> only enable the tunnel offload, then the application will get the
> >>> knowledge that it doesn't make sense to even try inserting "RSS +
> >>> MARK" flows. It just can skip useless actions. But if the PMD
> >>> doesn't support the method, the application will see ENOTSUP and
> >>> handle this
> >>> gracefully: it will make no assumptions about what's guaranteed to
> >>> be supported and what's not and will just keep on its old behavior:
> >>> try to insert a flow, fail, fall back to another type of flow.
> >>>
> >
> > I fully agree with your example, and think that this is the way to go,
> > application should supply as much info as possible during startup.
> 
> Right.
> 
> > My question/comment is the negotiated result means that all of the
> > actions are supported on the same rule?
> > for example if application wants to add mark and tag on the same rule.
> > (I know it doesn't make much sense) and the PMD can support both of
> > them but not on the same rule, what should it return?
> > Or for example if using the mark can only be supported if no decap
> > action is set on this rule what should be the result?
> >  From my undstanding this function is only to let the PMD know that on
> > some rules the application will use those actions, the checking if the
> > action combination is valid only happens on validate function right?
> 
> This API does not bind itself to flow API. It's *not* about enabling support for
> metadata *actions* (they are conducted entirely *inside* the NIC). It's
> about enabling *delivery* of metadata from the NIC to host.
>

Good point so why not use the same logic as the metadata and register it?
Since in any case, this is something in the mbuf so maybe this should be the answer?
 
> Say, you insert a flow rule to mark some packets. The NIC, internally (in the
> e-switch) adds the mark to matching packets. Yes, in the boundaries of the
> NIC HW, the packets bear the mark on them. It has been set, yes. But when
> time comes to *deliver* the packets to the host, the NIC (at least, in net/sfc
> case) has two options: either provide only a small chunk of the metadata for
> each packet *to the host*, which doesn't include mark ID, flag and RSS hash,
> OR, alternatively, provide the full set of metadata. In the former option, the
> mark is simply not delivered.
> Once again: it *has been set*, but simply will not be *delivered to the host*.
> 
> So, this API is about negotiating *delivery* of metadata. In pure technical
> sense. And the set of flags that this API returns indicates which kinds of
> metadata the NIC will be able to deliver simultaneously.
> 
> For example, as I understand, in the case of tunnel offload, MLX5 claims Rx
> mark entirely for tunnel ID metadata, so, if an application requests "MARK |
> TUNNEL_ID" with this API, this PMD should probably want to respond with
> just "TUNNEL_ID". The application will see the response and realise that,
> even if it adds its *own* (user) action MARK to a flow and if the flow is not
> rejected by the PMD, it won't be able to see the mark in the received mbufs
> (or the mark will be incorrect).
>
So what should the application do if on some flows it wants MARK and on other FLAG?
From DPDK viewpoint both of them can't be shared on the same rule
(they are using the same space in mbuf) so the application will never
ask for both of them in the same rule but he can on some rules ask for mark
while on other request for FLAG, even in your code you added both of them.

So what should the PMD return if it can support both of them just not at the same
rule?

One option is to document that the supported values are not per rule but for the entire
port. For example in the example you gave MLX5 will support mark + flag but will not
support mark + tunnel.

Also considering your example, the negotiation may result in subpar result.
taking your example the PMD returned  TUNNEL_ID maybe application would prefer
to have the mark and not the TUNNEL_ID. I understand that application can check
and try again with just the MARK. 
You are inserting logic to the PMD, maybe the function should just fail maybe
returning the conflicting items?


 
> But some other PMDs (net/sfc, for instance) claim only a small fraction of bits
> in Rx mark to deliver tunnel ID information. Remaining bits are still available
> for delivery of *user* mark ID. Please see an example at
> https://patches.dpdk.org/project/dpdk/patch/20210929205730.775-2-
> ivan.malov@oktetlabs.ru/
> . In this case, the PMD may want to return both flags in the response:
> "MARK | TUNNEL_ID". This way, the application knows that both features
> are enabled and available for use.
> 
> Now. I anticipate more questions asking why wouldn't we prefer flow API
> terminology or why wouldn't we add an API for negotiating support for
> metadata *actions* and not just metadata *delivery*. There's an answer.
> Always has been.
> 
> The thing is, the use of *actions* is very complicated. For example, the PMD
> may support action MARK for "transfer" flows but not for non-"transfer"
> ones. Also, simultaneous use of multiple different metadata actions may not
> be possible. And, last but not least, if we force the application to check
> support for *actions* on action-after-action basis, the order of checks will be
> very confusing to applications.
> 
> Previously, in this thread, Thomas suggested to go for exactly this type of
> API, to check support for actions one-by-one, without any context
> ("transfer" / non-"transfer"). I'm afraid, this won't be OK.
> 
+1 to keeping it as a separated API. (I agree actions limitation are very complex metrix)

> >
> > In any case I think this is good idea and I will see how we can add a
> > more generic approach of this API to the new API that I'm going to present.
> >
> >
> >>> So no breakages with this API.
> >>>
> >>>>
> >>>> Please see more comments inline.
> >>>>
> >>>> Thanks,
> >>>> Ori
> >>>>
> >>>>> -----Original Message-----
> >>>>> From: Ivan Malov <ivan.malov@oktetlabs.ru>
> >>>>> Sent: Thursday, September 23, 2021 2:20 PM
> >>>>> Subject: [PATCH v3 1/5] ethdev: add API to negotiate delivery of
> >>>>> Rx meta data
> >>>>>
> >>>>> Delivery of mark, flag and the likes might affect small packet
> >>>>> performance.
> >>>>> If these features are disabled by default, enabling them in
> >>>>> started state without causing traffic disruption may not always be
> possible.
> >>>>>
> >>>>> Let applications negotiate delivery of Rx meta data beforehand.
> >>>>>
> >>>>> Signed-off-by: Ivan Malov <ivan.malov@oktetlabs.ru>
> >>>>> Reviewed-by: Andrew Rybchenko
> <andrew.rybchenko@oktetlabs.ru>
> >>>>> Reviewed-by: Andy Moreton <amoreton@xilinx.com>
> >>>>> Acked-by: Ray Kinsella <mdr@ashroe.eu>
> >>>>> Acked-by: Jerin Jacob <jerinj@marvell.com>
> >>>>> ---
> >>>>>    app/test-flow-perf/main.c              | 21 ++++++++++++
> >>>>>    app/test-pmd/testpmd.c                 | 26 +++++++++++++++
> >>>>>    doc/guides/rel_notes/release_21_11.rst |  9 ++++++
> >>>>>    lib/ethdev/ethdev_driver.h             | 19 +++++++++++
> >>>>>    lib/ethdev/rte_ethdev.c                | 25 ++++++++++++++
> >>>>>    lib/ethdev/rte_ethdev.h                | 45
> >>>>> ++++++++++++++++++++++++++
> >>>>>    lib/ethdev/rte_flow.h                  | 12 +++++++
> >>>>>    lib/ethdev/version.map                 |  3 ++
> >>>>>    8 files changed, 160 insertions(+)
> >>>>>
> >>>>> diff --git a/app/test-flow-perf/main.c b/app/test-flow-perf/main.c
> >>>>> index 9be8edc31d..48eafffb1d 100644
> >>>>> --- a/app/test-flow-perf/main.c
> >>>>> +++ b/app/test-flow-perf/main.c
> >>>>> @@ -1760,6 +1760,27 @@ init_port(void)
> >>>>>            rte_exit(EXIT_FAILURE, "Error: can't init mbuf
> >>>>> pool\n");
> >>>>>
> >>>>>        for (port_id = 0; port_id < nr_ports; port_id++) {
> >>>>> +        uint64_t rx_meta_features = 0;
> >>>>> +
> >>>>> +        rx_meta_features |= RTE_ETH_RX_META_USER_FLAG;
> >>>>> +        rx_meta_features |= RTE_ETH_RX_META_USER_MARK;
> >>>>> +
> >>>>> +        ret = rte_eth_rx_meta_negotiate(port_id,
> >>>>> &rx_meta_features);
> >>>>> +        if (ret == 0) {
> >>>>> +            if (!(rx_meta_features &
> >>>>> RTE_ETH_RX_META_USER_FLAG)) {
> >>>>> +                printf(":: flow action FLAG will not affect Rx
> >>>>> mbufs on port=%u\n",
> >>>>> +                       port_id);
> >>>>> +            }
> >>>>> +
> >>>>> +            if (!(rx_meta_features &
> >>>>> RTE_ETH_RX_META_USER_MARK)) {
> >>>>> +                printf(":: flow action MARK will not affect Rx
> >>>>> mbufs on port=%u\n",
> >>>>> +                       port_id);
> >>>>> +            }
> >>>>> +        } else if (ret != -ENOTSUP) {
> >>>>> +            rte_exit(EXIT_FAILURE, "Error when negotiating Rx
> >>>>> meta features on port=%u: %s\n",
> >>>>> +                 port_id, rte_strerror(-ret));
> >>>>> +        }
> >>>>> +
> >>>>>            ret = rte_eth_dev_info_get(port_id, &dev_info);
> >>>>>            if (ret != 0)
> >>>>>                rte_exit(EXIT_FAILURE, diff --git
> >>>>> a/app/test-pmd/testpmd.c b/app/test-pmd/testpmd.c index
> >>>>> 97ae52e17e..7a8da3d7ab 100644
> >>>>> --- a/app/test-pmd/testpmd.c
> >>>>> +++ b/app/test-pmd/testpmd.c
> >>>>> @@ -1485,10 +1485,36 @@ static void
> >>>>>    init_config_port_offloads(portid_t pid, uint32_t socket_id)  {
> >>>>>        struct rte_port *port = &ports[pid];
> >>>>> +    uint64_t rx_meta_features = 0;
> >>>>>        uint16_t data_size;
> >>>>>        int ret;
> >>>>>        int i;
> >>>>>
> >>>>> +    rx_meta_features |= RTE_ETH_RX_META_USER_FLAG;
> >>>>> +    rx_meta_features |= RTE_ETH_RX_META_USER_MARK;
> >>>>> +    rx_meta_features |= RTE_ETH_RX_META_TUNNEL_ID;
> >>>>> +
> >>>>> +    ret = rte_eth_rx_meta_negotiate(pid, &rx_meta_features);
> >>>>> +    if (ret == 0) {
> >>>>> +        if (!(rx_meta_features & RTE_ETH_RX_META_USER_FLAG)) {
> >>>>> +            TESTPMD_LOG(INFO, "Flow action FLAG will not
> >>>>> affect Rx mbufs on port %u\n",
> >>>>> +                    pid);
> >>>>> +        }
> >>>>> +
> >>>>> +        if (!(rx_meta_features & RTE_ETH_RX_META_USER_MARK))
> >>>>> {
> >>>>> +            TESTPMD_LOG(INFO, "Flow action MARK will not
> >>>>> affect Rx mbufs on port %u\n",
> >>>>> +                    pid);
> >>>>> +        }
> >>>>> +
> >>>>> +        if (!(rx_meta_features & RTE_ETH_RX_META_TUNNEL_ID)) {
> >>>>> +            TESTPMD_LOG(INFO, "Flow tunnel offload support
> >>>>> might be limited or unavailable on port %u\n",
> >>>>> +                    pid);
> >>>>> +        }
> >>>>> +    } else if (ret != -ENOTSUP) {
> >>>>> +        rte_exit(EXIT_FAILURE, "Error when negotiating Rx meta
> >>>>> features on port %u: %s\n",
> >>>>> +             pid, rte_strerror(-ret));
> >>>>> +    }
> >>>>> +
> >>>>>        port->dev_conf.txmode = tx_mode;
> >>>>>        port->dev_conf.rxmode = rx_mode;
> >>>>>
> >>>>> diff --git a/doc/guides/rel_notes/release_21_11.rst
> >>>>> b/doc/guides/rel_notes/release_21_11.rst
> >>>>> index 19356ac53c..6674d4474c 100644
> >>>>> --- a/doc/guides/rel_notes/release_21_11.rst
> >>>>> +++ b/doc/guides/rel_notes/release_21_11.rst
> >>>>> @@ -106,6 +106,15 @@ New Features
> >>>>>      Added command-line options to specify total number of
> >>>>> processes and
> >>>>>      current process ID. Each process owns subset of Rx and Tx queues.
> >>>>>
> >>>>> +* **Added an API to negotiate delivery of specific parts of Rx
> >>>>> +meta
> >>>>> +data**
> >>>>> +
> >>>>> +  A new API, ``rte_eth_rx_meta_negotiate()``, was added.
> >>>>> +  The following parts of Rx meta data were defined:
> >>>>> +
> >>>>> +  * ``RTE_ETH_RX_META_USER_FLAG``
> >>>>> +  * ``RTE_ETH_RX_META_USER_MARK``
> >>>>> +  * ``RTE_ETH_RX_META_TUNNEL_ID``
> >>>>> +
> >>>>>
> >>>>>    Removed Items
> >>>>>    -------------
> >>>>> diff --git a/lib/ethdev/ethdev_driver.h
> >>>>> b/lib/ethdev/ethdev_driver.h index 40e474aa7e..96e0c60cae 100644
> >>>>> --- a/lib/ethdev/ethdev_driver.h
> >>>>> +++ b/lib/ethdev/ethdev_driver.h
> >>>>> @@ -789,6 +789,22 @@ typedef int (*eth_get_monitor_addr_t)(void
> >>>>> *rxq, typedef int (*eth_representor_info_get_t)(struct rte_eth_dev
> >>>>> *dev,
> >>>>>        struct rte_eth_representor_info *info);
> >>>>>
> >>>>> +/**
> >>>>> + * @internal
> >>>>> + * Negotiate delivery of specific parts of Rx meta data.
> >>>>> + *
> >>>>> + * @param dev
> >>>>> + *   Port (ethdev) handle
> >>>>> + *
> >>>>> + * @param[inout] features
> >>>>> + *   Feature selection buffer
> >>>>> + *
> >>>>> + * @return
> >>>>> + *   Negative errno value on error, zero otherwise  */ typedef
> >>>>> +int (*eth_rx_meta_negotiate_t)(struct rte_eth_dev *dev,
> >>>>> +                       uint64_t *features);
> >>>>> +
> >>>>>    /**
> >>>>>     * @internal A structure containing the functions exported by
> >>>>> an Ethernet driver.
> >>>>>     */
> >>>>> @@ -949,6 +965,9 @@ struct eth_dev_ops {
> >>>>>
> >>>>>        eth_representor_info_get_t representor_info_get;
> >>>>>        /**< Get representor info. */
> >>>>> +
> >>>>> +    eth_rx_meta_negotiate_t rx_meta_negotiate;
> >>>>> +    /**< Negotiate delivery of specific parts of Rx meta data. */
> >>>>>    };
> >>>>>
> >>>>>    /**
> >>>>> diff --git a/lib/ethdev/rte_ethdev.c b/lib/ethdev/rte_ethdev.c
> >>>>> index daf5ca9242..49cb84d64c 100644
> >>>>> --- a/lib/ethdev/rte_ethdev.c
> >>>>> +++ b/lib/ethdev/rte_ethdev.c
> >>>>> @@ -6310,6 +6310,31 @@ rte_eth_representor_info_get(uint16_t
> >>>>> port_id,
> >>>>>        return eth_err(port_id, (*dev->dev_ops-
> >>>>>> representor_info_get)(dev, info));  }
> >>>>>
> >>>>> +int
> >>>>> +rte_eth_rx_meta_negotiate(uint16_t port_id, uint64_t *features) {
> >>>>> +    struct rte_eth_dev *dev;
> >>>>> +
> >>>>> +    RTE_ETH_VALID_PORTID_OR_ERR_RET(port_id, -ENODEV);
> >>>>> +    dev = &rte_eth_devices[port_id];
> >>>>> +
> >>>>> +    if (dev->data->dev_configured != 0) {
> >>>>> +        RTE_ETHDEV_LOG(ERR,
> >>>>> +            "The port (id=%"PRIu16") is already configured\n",
> >>>>> +            port_id);
> >>>>> +        return -EBUSY;
> >>>>> +    }
> >>>>> +
> >>>>> +    if (features == NULL) {
> >>>>> +        RTE_ETHDEV_LOG(ERR, "Invalid features (NULL)\n");
> >>>>> +        return -EINVAL;
> >>>>> +    }
> >>>>> +
> >>>>> +    RTE_FUNC_PTR_OR_ERR_RET(*dev->dev_ops-
> >rx_meta_negotiate,
> >>>>> -ENOTSUP);
> >>>>> +    return eth_err(port_id,
> >>>>> +               (*dev->dev_ops->rx_meta_negotiate)(dev,
> >>>>> +features)); }
> >>>>> +
> >>>>>    RTE_LOG_REGISTER_DEFAULT(rte_eth_dev_logtype, INFO);
> >>>>>
> >>>>>    RTE_INIT(ethdev_init_telemetry) diff --git
> >>>>> a/lib/ethdev/rte_ethdev.h b/lib/ethdev/rte_ethdev.h index
> >>>>> 1da37896d8..8467a7a362 100644
> >>>>> --- a/lib/ethdev/rte_ethdev.h
> >>>>> +++ b/lib/ethdev/rte_ethdev.h
> >>>>> @@ -4888,6 +4888,51 @@ __rte_experimental  int
> >>>>> rte_eth_representor_info_get(uint16_t port_id,
> >>>>>                     struct rte_eth_representor_info *info);
> >>>>>
> >>>>> +/** The ethdev sees flagged packets if there are flows with
> >>>>> +action FLAG. */ #define RTE_ETH_RX_META_USER_FLAG
> (UINT64_C(1) <<
> >>>>> +0)
> >>>>> +
> >>>>> +/** The ethdev sees mark IDs in packets if there are flows with
> >>>>> +action MARK. */ #define RTE_ETH_RX_META_USER_MARK
> >> (UINT64_C(1) <<
> >>>>> +1)
> >>>>> +
> >>>>> +/** The ethdev detects missed packets if there are "tunnel_set"
> >>>>> +flows in use. */ #define RTE_ETH_RX_META_TUNNEL_ID
> (UINT64_C(1)
> >> <<
> >>>>> +2)
> >>>>> +
> >>>>> +/**
> >>>>> + * @warning
> >>>>> + * @b EXPERIMENTAL: this API may change without prior notice
> >>>>> + *
> >>>>> + * Negotiate delivery of specific parts of Rx meta data.
> >>>>> + *
> >>>>> + * Invoke this API before the first rte_eth_dev_configure()
> >>>>> +invocation
> >>>>> + * to let the PMD make preparations that are inconvenient to do
> later.
> >>>>> + *
> >>>>> + * The negotiation process is as follows:
> >>>>> + *
> >>>>> + * - the application requests features intending to use at least
> >>>>> +some of them;
> >>>>> + * - the PMD responds with the guaranteed subset of the requested
> >>>>> +feature set;
> >>>>> + * - the application can retry negotiation with another set of
> >>>>> +features;
> >>>>> + * - the application can pass zero to clear the negotiation
> >>>>> +result;
> >>>>> + * - the last negotiated result takes effect upon the ethdev start.
> >>>>> + *
> >>>>> + * If this API is unsupported, the application should gracefully
> >>>>> ignore that.
> >>>>> + *
> >>>>> + * @param port_id
> >>>>> + *   Port (ethdev) identifier
> >>>>> + *
> >>>>> + * @param[inout] features
> >>>>> + *   Feature selection buffer
> >>>>> + *
> >>>>> + * @return
> >>>>> + *   - (-EBUSY) if the port can't handle this in its current
> >>>>> +state;
> >>>>> + *   - (-ENOTSUP) if the method itself is not supported by the
> >>>>> +PMD;
> >>>>> + *   - (-ENODEV) if *port_id* is invalid;
> >>>>> + *   - (-EINVAL) if *features* is NULL;
> >>>>> + *   - (-EIO) if the device is removed;
> >>>>> + *   - (0) on success
> >>>>> + */
> >>>>> +__rte_experimental
> >>>>> +int rte_eth_rx_meta_negotiate(uint16_t port_id, uint64_t
> >>>>> +*features);
> >>>>
> >>>> I don't think meta is the best name since we also have meta item
> >>>> and the word meta can be used in other cases.
> >>>
> >>> I'm no expert in naming. What could be a better term for this?
> >>> Personally, I'd rather not perceive "meta" the way you describe.
> >>> It's not just "meta". It's "rx_meta", and the flags supplied with
> >>> this API provide enough context to explain what it's all about.
> >>
> >> Thinking overnight about it I'd suggest full "metadata".
> >> Yes, it will name a bit longer, but less confusing versus term META
> >> already used in flow API.
> >>
> > Following my above comments, I think it should be part of the new API
> > but in any case what about rx_flow_action_negotiate?
> 
> See my thoughts above. It makes no sense to negotiate *support for
> actions*. Existing "rte_flow_validate()" already does that job. The new
> "negotiate Rx metadata* API is all about *delivery* of metadata which is
> supposed to be *already* set for the packets *inside* the NIC. So, we
> negotiate *delivery from the NIC to the host*. Nothing more.
> 
Agree with your comment but then maybe we should go to the register
approach just like metadata?

Best,
Ori
> >
> >> Andrew.
> > Best,
> > Ori
> >
> 
> --
> Ivan M