Re: [PATCH 2/6] net/hns3: fix inconsistent enabled RSS behavior

[Thomas Monjalon <thomas@monjalon.net>]

23/03/2022 12:04, lihuisong (C):
> 在 2022/3/23 17:14, Thomas Monjalon 写道:
> > 23/03/2022 04:05, lihuisong (C):
> >> 在 2022/3/23 1:13, Thomas Monjalon 写道:
> >>> 21/03/2022 08:14, lihuisong (C):
> >>>> 2022/3/10 16:08, lihuisong (C):
> >>>>> 2022/3/9 17:55, Ori Kam:
> >>>>>> From: lihuisong (C) <lihuisong@huawei.com>
> >>>>>>> 2022/3/3 10:47, lihuisong (C):
> >>>>>>>> 2022/3/2 22:07, Ori Kam:
> >>>>>>>>> From: lihuisong (C) <lihuisong@huawei.com>
> >>>>>>>>>> 2022/3/1 0:42, Ferruh Yigit:
> >>>>>>>>>>> On 2/28/2022 3:21 AM, Min Hu (Connor) wrote:
> >>>>>>>>>>>> From: Huisong Li <lihuisong@huawei.com>
> >>>>>>>>>>>>
> >>>>>>>>>>>> RSS will not be enabled if the RTE_ETH_MQ_RX_RSS_FLAG isn't be
> >>>>>>>>>>>> set in
> >>>>>>>>>>>> dev_configure phase. However, if this flag isn't set, RSS can be
> >>>>>>>>>>>> enabled
> >>>>>>>>>>>> through the ethdev ops and rte_flow API. This behavior is
> >>>>>>>>>>>> contrary to
> >>>>>>>>>>>> each
> >>>>>>>>>>>> other.
> >>>>>>>>>>>>
> >>>>>>>>>>>> Fixes: c37ca66f2b27 ("net/hns3: support RSS")
> >>>>>>>>>>>> Cc: stable@dpdk.org
> >>>>>>>>>>>>
> >>>>>>>>>>>> Signed-off-by: Huisong Li <lihuisong@huawei.com>
> >>>>>>>>>>> Hi Huisong, Connor,
> >>>>>>>>>>>
> >>>>>>>>>>> Let's get a little more feedback for this patch, cc'ed more people.
> >>>>>>>>>>>
> >>>>>>>>>>> To enable RSS, multi queue mode should be set to
> >>>>>>>>>>> 'RTE_ETH_MQ_RX_RSS_FLAG'.
> >>>>>>>>>>>
> >>>>>>>>>>> But I wonder if it is required to configure RSS via flow API,
> >>>>>>>>>> I do not know the original purpose of adding the RSS
> >>>>>>>>>> configuration in
> >>>>>>>>>> flow API.
> >>>>>>>>>>
> >>>>>>>>> The purpose is simple, this allow to create RSS per rule and not a
> >>>>>>>>> global one.
> >>>>>>>>> For example create RSS that sends TCP to some queues while othe RSS
> >>>>>>>>> will send
> >>>>>>>>> UDP traffic to different queues.
> >>>>>>>> I'm a little confused now. The "per rule" also seems to be a global
> >>>>>>>> configuration.
> >>>>>>>> Example:
> >>>>>>>>     - start PMD with 0,1,2,3
> >>>>>>>>     - create TCP packets to 2,3 queues. At this moment, only 2,3 queues
> >>>>>>>> can be received for other types of packets.
> >>>>>>>> Because this rule is implemented by modifying the entry of the
> >>>>>>>> redirection table which is global for this device.
> >>>>>>> Hi, Ori and Stephen.
> >>>>>>> Can you help me clear up the confusion above? If some NICs behave like
> >>>>>>> this, what should we do about it?
> >>>>>> I'm not sure I understand the issue, maybe it is releated to some
> >>>>>> HW/PMD limitation.
> >>>>>> In your example non TCP traffic will be routed to one of the 4 queues
> >>>>>> (0,1,2,3),
> >>>>>> While TCP traffic will only be routed to queues 2,3.
> >>>>>>
> >>>>>> Now I can add new rule that matches on UDP packet and RSS to queue 0
> >>>>>> and 3 in this case:
> >>>>>> TCP packets will be routed to queues 0,3.
> >>>>>> UDP packets will be routed to queues 2,3.
> >>>>>> All the rest of the traffic will be routed to queues 0,1,2,3
> >>>>>>
> >>>>>> And just to be clear if now I add a rule to match all packets in
> >>>>>> higher priority,
> >>>>>> with RSS to queues 1,2. Then all traffic will be routed to queues 1,2.
> >>>>>>
> >>>>>> At least this is what is expected, from API point of view.
> >>>>>>
> >>>>>> Best,
> >>>>>> Ori
> >>>>> Thank you for your answer. I understand it.
> >>>>> hns3 PMD cannot implement the above functions due to hardware limitation.
> >>>>> we may need add a check that specified RSS queues cannot be supported
> >>>>> when specified packets types.
> >>>>> And only the packet type is specified, which meets the requirements of
> >>>>> rte_flow API.
> >>>>> The check for the RTE_ETH_MQ_RX_RSS_FLAG flag in rte_flow is not correct.
> >>>>> Thanks, Ori and Stephen😁
> >>>>>
> >>>>> But, I think, it is necessary for the '.rss_hash_update' and
> >>>>> '.reta_update' APIs
> >>>>> in eth_dev_ops to verify this flag. What do you think? @Thomas,
> >>>>> @Ferruh, @Ori and @Stephen.
> >>>> What's your take on it? I am looking forward to your reply. Thanks!
> >>> I am not sure why you want to check this flag.
> >> I want to make sure that the behavior that PMD configured RSS is
> >> consistent across different interfaces. The RTE_ETH_MQ_RX_RSS_FLAG
> >> flag is a switch to enable RSS hash. If the switch isn't open, some
> >> PMD do not configure RSS function. I think the consistency is necessary.
> >> If not set RSS muti-queue mode, it is unnecessary to configure RSS.
> >>
> >>> I can imagine we configure the hash and the table before enabling RSS
> >>> with the RTE_ETH_MQ_RX_RSS_FLAG flag.
> >> The flag is derived from dev_configure() which also configures
> >> hash and key. I don't think it makes sense to configure hash and
> >> reta before calling dev_configure. Because they'll be updated.
> >> This is similar to configuring mtu.
> > OK I see your point.
> > So you would like to return an error in RSS functions
> > if the flag RTE_ETH_MQ_RX_RSS_FLAG is not set?
> Yes
> > Should it be checked in ethdev library or PMDs?
> I think it's better to put it in the ethdev layer if we do it.
> Should we add this check in 'rss_hash_update' and 'reta_update' APIs?

I'm OK with adding the check in ethdev.