netdev - Re: [PATCH net v3 3/3] bnxt_en: handle tpa

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Message-ID: <fedc8606-b3bc-4fb1-8803-a004cb24216e@davidwei.uk>
Date: Wed, 11 Dec 2024 08:10:30 -0800
From: David Wei <dw@...idwei.uk>
To: Yunsheng Lin <linyunsheng@...wei.com>, netdev@...r.kernel.org,
 Michael Chan <michael.chan@...adcom.com>,
 Andy Gospodarek <andrew.gospodarek@...adcom.com>,
 Somnath Kotur <somnath.kotur@...adcom.com>
Cc: Andrew Lunn <andrew+netdev@...n.ch>, "David S. Miller"
 <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>
Subject: Re: [PATCH net v3 3/3] bnxt_en: handle tpa_info in queue API
 implementation

On 2024-12-11 04:32, Yunsheng Lin wrote:
> On 2024/12/11 2:14, David Wei wrote:
>> On 2024-12-10 04:25, Yunsheng Lin wrote:
>>> On 2024/12/4 12:10, David Wei wrote:
>>>
>>>>  	bnxt_copy_rx_ring(bp, rxr, clone);
>>>> @@ -15563,6 +15580,8 @@ static int bnxt_queue_stop(struct net_device *dev, void *qmem, int idx)
>>>>  	bnxt_hwrm_rx_agg_ring_free(bp, rxr, false);
>>>>  	rxr->rx_next_cons = 0;
>>>>  	page_pool_disable_direct_recycling(rxr->page_pool);
>>>> +	if (bnxt_separate_head_pool())
>>>> +		page_pool_disable_direct_recycling(rxr->head_pool);
>>>
>>> Hi, David
>>> As mentioned in [1], is the above page_pool_disable_direct_recycling()
>>> really needed?
>>>
>>> Is there any NAPI API called in the implementation of netdev_queue_mgmt_ops?
>>> It doesn't seem obvious there is any NAPI API like napi_enable() &
>>> ____napi_schedule() that is called in bnxt_queue_start()/bnxt_queue_stop()/
>>> bnxt_queue_mem_alloc()/bnxt_queue_mem_free() through code reading.
>>>
>>> 1. https://lore.kernel.org/all/c2b306af-4817-4169-814b-adbf25803919@huawei.com/
>>
>> Hi Yunsheng, there are explicitly no napi_enable/disable() calls in the
>> bnxt implementation of netdev_queue_mgmt_ops due to ... let's say HW/FW
>> quirks. I looked back at my discussions w/ Broadcom, and IIU/RC
>> bnxt_hwrm_vnic_update() will prevent any work from coming into the rxq
>> that I'm trying to stop. Calling napi_disable() has unintended side
>> effects on the Tx side.
> 
> It seems that bnxt_hwrm_vnic_update() sends a VNIC_UPDATE cmd to disable
> a VNIC? and a napi_disable() is not needed?

Correct.

> Is it possible that there may
> be some pending NAPI work is still being processed after bnxt_hwrm_vnic_update()
> is called?

Possibly, I don't know the details of how the HW works.

At the time I just wanted something to work, and not having
napi_enable/disable() made it work. :) Looking back though it does seem
odd, so I'll try putting it back.

> 
>>
>> The intent of the call to page_pool_disable_direct_recycling() is to
>> prevent pages from the old page pool from being returned into the fast
>> cache. These pages must be returned via page_pool_return_page() so that
>> the it can eventually be freed in page_pool_release_retry().
>>
>> I'm going to take a look at your discussions in [1] and respond there.
> 
> Thanks.