Re: [dpdk-dev] [PATCH 2/3] app/testpmd: remove forwarding config from parsing Rx and Tx

["Li, Xiaoyun" <xiaoyun.li@intel.com>]

> -----Original Message-----
> From: oulijun <oulijun@huawei.com>
> Sent: Thursday, March 25, 2021 11:04
> To: Li, Xiaoyun <xiaoyun.li@intel.com>; Yigit, Ferruh <ferruh.yigit@intel.com>
> Cc: dev@dpdk.org; linuxarm@openeuler.org
> Subject: Re: [PATCH 2/3] app/testpmd: remove forwarding config from parsing
> Rx and Tx
> 
> 
> 
> 在 2021/3/24 9:44, Li, Xiaoyun 写道:
> >
> >
> >> -----Original Message-----
> >> From: oulijun <oulijun@huawei.com>
> >> Sent: Wednesday, March 24, 2021 09:01
> >> To: Li, Xiaoyun <xiaoyun.li@intel.com>; Yigit, Ferruh
> >> <ferruh.yigit@intel.com>
> >> Cc: dev@dpdk.org; linuxarm@openeuler.org
> >> Subject: Re: [PATCH 2/3] app/testpmd: remove forwarding config from
> >> parsing Rx and Tx
> >>
> >>
> >>
> >> 在 2021/3/23 15:50, Li, Xiaoyun 写道:
> >>> Hi
> >>>
> >>>> -----Original Message-----
> >>>> From: Lijun Ou <oulijun@huawei.com>
> >>>> Sent: Friday, March 5, 2021 18:22
> >>>> To: Yigit, Ferruh <ferruh.yigit@intel.com>
> >>>> Cc: Li, Xiaoyun <xiaoyun.li@intel.com>; dev@dpdk.org;
> >>>> linuxarm@openeuler.org
> >>>> Subject: [PATCH 2/3] app/testpmd: remove forwarding config from
> >>>> parsing Rx and Tx
> >>>>
> >>>> From: Huisong Li <lihuisong@huawei.com>
> >>>>
> >>>
> >>> The commit message should be more simple and avoids grammar mistakes.
> >>>
> >> All right, I will simply it.
> >>>> The "fwd_config_setup()" function does release and apply for memory
> >>>> of forwarding flows, and re-establish these streams when rxq/txq or
> >>>> rxd/txd is changed. The function is also called by
> >>>> "start_packet_forwarding()" when user executes "start" cmd.
> >>>> All changes for rxq/txq or rxd/txd can be updated uniformly when
> >>>> this command is executed. Therefore, it is a little redundant in
> >>>> the
> >> "cmd_config_rx_tx_parsed"
> >>>> function.
> >>>
> >>> It's not redundant. This command may configure number of rxq/txq. So
> >>> the
> >> fwd streams map may change.
> >>> Then it's common to check the fwd streams after this command using
> >>> "show
> >> config fwd".
> >>> If you remove this fwd stream update, users can't get the correct
> >>> new fwd
> >> streams until they start the traffic.
> >>> But they may change a lot of things and want to check if the setting
> >>> is correct
> >> before they start the traffic.
> >>>
> >> Yes, you are right. It's really unfriendly.
> >>>>
> >>>> In addition, the forwarding stream under one TC is configured based
> >>>> on number of queues allocated to TC. And number of queues allocated
> >>>> to TC is updated after calling  "rte_eth_dev_configure"
> >>>> again. If the number of queues is reduced after configuring the
> >>>> DCB, and then, release and apply for stream memory, and
> >>>> reinitialize the forwarding stream under the DCB mode based on the old TC
> information.
> >>>> As a result, null pointer may be accessed.
> >>>
> >>> I think you should add "rte_eth_dev_configure " into
> >>> dcb_fwd_config_setup()
> >> before rte_eth_dev_get_dcb_info().
> >>>
> >>> And the commit message should be similar like the following:
> >>> Segment fault might happen after configuring queue number to less
> >>> because
> >> dcb_fwd_config_setup setup dcb based on old dcb info.
> >>> And dcb info can only update after rte_eth_dev_configure().
> >>> So this patch adds rte_eth_dev_configure() before
> >>> rte_eth_dev_get_dcb_info()
> >> to get updated dcb info to fix this issue.
> >>>
> >> Thank you for your advice. But the above adjustments may still not
> >> work for some drivers. The mapping between queues and TCs in these
> >> drivers is updated in the dev_start stage.
> >>
> >> I have an idea. We can move fwd_config_setup() to start_port(), which
> >> is called by main() and after starting ports This not only solves the
> >> segment fault, but also does not have the problem you mentioned above. I
> test it and it is ok.
> >>
> >> What do you think, xiaoyun?
> >
> > How can you fix the issue I mentioned?
> > You still need to start port first to see the updated fwd config.
> Yes. But it can make sure that users get the correct new fwd streams before
> executing the 'start' command.
> > And for those drivers, why does the mapping has to be updated in dev_start
> stage?
> > What does it need? Can't it be moved to dev_configure?
> The framework does not require that the configuration parameters transferred
> by the dev_configure API must be updated in the interface of driver. The driver
> can  verify the correctness of these parameters in the interface, and then
> complete the update in the dev_start stage. It depends on the design and need
> of the driver. Maybe it's more appropriate to put it in dev_configure, but now
> we can't ask all these drivers to modify the operation.

I still think it's driver's responsibility to configure DCB in dev_configure.

Calling fwd_config_setup here is because this command changes queue number. Users just change queue number so want to check fwd setup. It's a normal and reasonable behavior.
Starting port will be called in many situations. I don't think it's appropriate to call fwd_config_setup every time calling port_start. And you can't expect users know the fwd setup only change after port_start.

These are only my thoughts. If anyone else agrees you, they can give you ack.
> >>
> >>
> >>>>
> >>>> Like:
> >>>> set nbcore 4
> >>>> port stop all
> >>>> port config 0 dcb vt off 4 pfc on
> >>>> port start all
> >>>> port stop all
> >>>> port config all rxq 8
> >>>> port config all txq 8
> >>>>
> >>>> At the moment, a segmentation fault occurs.
> >>>>
> >>>> Fixes: ce8d561418d4 ("app/testpmd: add port configuration
> >>>> settings")
> >>>> Cc: stable@dpdk.org
> >>>>
> >>>> Signed-off-by: Huisong Li <lihuisong@huawei.com>
> >>>> Signed-off-by: Lijun Ou <oulijun@huawei.com>
> >>>> ---
> >>>> V1->V2:
> >>>> - use stream instead of flow
> >>>> ---
> >>>>    app/test-pmd/cmdline.c | 2 --
> >>>>    1 file changed, 2 deletions(-)
> >>>>
> >>>> diff --git a/app/test-pmd/cmdline.c b/app/test-pmd/cmdline.c index
> >>>> 4df0c32..e316f5c 100644
> >>>> --- a/app/test-pmd/cmdline.c
> >>>> +++ b/app/test-pmd/cmdline.c
> >>>> @@ -1837,8 +1837,6 @@ cmd_config_rx_tx_parsed(void *parsed_result,
> >>>>    		return;
> >>>>    	}
> >>>>
> >>>> -	fwd_config_setup();
> >>>> -
> >>>>    	init_port_config();
> >>>>
> >>>>    	cmd_reconfig_device_queue(RTE_PORT_ALL, 1, 1);
> >>>> --
> >>>> 2.7.4
> >>>
> >>> .
> >>>
> > .
> >