netdev - Re: [PATCH net-next 2/2] ice: Add inline flow director support for channels

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Message-ID: <135a75f8-2da9-407b-40b2-b84ecb229110@intel.com>
Date:   Fri, 11 Mar 2022 12:36:55 -0600
From:   "Samudrala, Sridhar" <sridhar.samudrala@...el.com>
To:     Jakub Kicinski <kuba@...nel.org>,
        Tony Nguyen <anthony.l.nguyen@...el.com>
CC:     <davem@...emloft.net>, Kiran Patil <kiran.patil@...el.com>,
        <netdev@...r.kernel.org>, <sudheer.mogilappagari@...el.com>,
        <amritha.nambiar@...el.com>, <jiri@...dia.com>,
        <leonro@...dia.com>,
        Bharathi Sreenivas <bharathi.sreenivas@...el.com>
Subject: Re: [PATCH net-next 2/2] ice: Add inline flow director support for
 channels

On 3/10/2022 10:34 PM, Jakub Kicinski wrote:
> On Thu, 10 Mar 2022 15:12:35 -0800 Tony Nguyen wrote:
>> Inline flow director can be configured for each TC via devlink
>> params based interface.
>>
>> /* Create 4 TCs */
>> tc qdisc add dev enp175s0f0 root mqprio num_tc 4 map 0 1 2 3 \
>>               queues 2@0 8@2 8@10 8@18 hw 1 mode channel
>>
>> /* Enable inline flow director for TC1 and TC2 */
>> devlink dev param set pci/0000:af:00.0 \
>>          name tc_inline_fd value 6 cmode runtime
>>
>> /* Dump inline flow director setting */
>> devlink dev param show  pci/0000:af:00.0 name tc_inline_fd
>> pci/0000:af:00.0:
>>    name tc2_inline_fd type driver-specific
>>      values:
>>        cmode runtime value 6
> Why is this in devlink and not ethtool?

This is 16bit value with each bit representing a TC and is used to
enable/disable inline flow director per queue group or TC.
tc mqprio command allows creating upto 16 TCs.

My understanding is that ethtool parameters are per netedev or per-queue,
but we don't have good way to configure per-queue_group parameters
via ethtool. So we went with devlink.


>
> All devlink params must be clearly documented.

Based on the discussion in the other thread, we will make this a
devlink parameter that is registered at probe time
    https://lore.kernel.org/netdev/Yit3sLq6b+ZNZ07j@unreal/
Will add documentation in the next revision.
Hope this is OK.

-Sridhar