netdev - Re: [PATCH net-next v7 7/9] eth: bnxt: allow providers to set rx buf size

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Message-ID: <c97d2c95-31c5-4bf6-b58f-552e85314056@gmail.com>
Date: Thu, 11 Dec 2025 01:39:25 +0000
From: Pavel Begunkov <asml.silence@...il.com>
To: Jakub Kicinski <kuba@...nel.org>
Cc: netdev@...r.kernel.org, "David S . Miller" <davem@...emloft.net>,
 Eric Dumazet <edumazet@...gle.com>, Paolo Abeni <pabeni@...hat.com>,
 Jonathan Corbet <corbet@....net>, Michael Chan <michael.chan@...adcom.com>,
 Pavan Chebbi <pavan.chebbi@...adcom.com>, Andrew Lunn
 <andrew+netdev@...n.ch>, Alexei Starovoitov <ast@...nel.org>,
 Daniel Borkmann <daniel@...earbox.net>,
 Jesper Dangaard Brouer <hawk@...nel.org>,
 John Fastabend <john.fastabend@...il.com>,
 Ilias Apalodimas <ilias.apalodimas@...aro.org>, Shuah Khan
 <shuah@...nel.org>, Mina Almasry <almasrymina@...gle.com>,
 Stanislav Fomichev <sdf@...ichev.me>, Yue Haibing <yuehaibing@...wei.com>,
 David Wei <dw@...idwei.uk>, Haiyue Wang <haiyuewa@....com>,
 Jens Axboe <axboe@...nel.dk>, Joe Damato <jdamato@...tly.com>,
 Simon Horman <horms@...nel.org>, Vishwanath Seshagiri <vishs@...com>,
 linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
 bpf@...r.kernel.org, linux-kselftest@...r.kernel.org,
 io-uring@...r.kernel.org, dtatulea@...dia.com
Subject: Re: [PATCH net-next v7 7/9] eth: bnxt: allow providers to set rx buf
 size

On 12/2/25 18:58, Jakub Kicinski wrote:
> On Sun, 30 Nov 2025 23:35:22 +0000 Pavel Begunkov wrote:
>> +static ssize_t bnxt_get_rx_buf_size(struct bnxt *bp, int rxq_idx)
>> +{
>> +	struct netdev_rx_queue *rxq = __netif_get_rx_queue(bp->dev, rxq_idx);
>> +	size_t rx_buf_size;
>> +
>> +	rx_buf_size = rxq->mp_params.rx_buf_len;
>> +	if (!rx_buf_size)
>> +		return BNXT_RX_PAGE_SIZE;
> 
> I'd like to retain my cfg objects in the queue API, if you don't mind.
> I guess we just need the way for drivers to fill in the defaults and
> then plumb them into the ops.

It was problematic, I wanted to split it into more digestible chunks.
My main problem is that it was not really optional and could break
drivers that don't even care about this qcfg len option but allow
setting it device-wise via ethtool, and I won't even have a way to
test them.

Maybe there is a way to strip down qcfg and only apply it to marked
queue api enabled drivers for now, and then extend the idea it in
the future. E.g.

set 1) optional and for qapi drivers only
set 2) patch up all qapi drivers and make it mandatory
set 3) convert all other drivers that set the length.

I can take a look at implementing 1) in this series. It should help
to keep complexity manageable.

...
>>   static int bnxt_queue_mem_alloc(struct net_device *dev, void *qmem, int idx)
>>   {
>>   	struct bnxt_rx_ring_info *rxr, *clone;
>>   	struct bnxt *bp = netdev_priv(dev);
>>   	struct bnxt_ring_struct *ring;
>> +	ssize_t rx_buf_size;
>>   	int rc;
>>   
>>   	if (!bp->rx_ring)
>>   		return -ENETDOWN;
>>   
>> +	rx_buf_size = bnxt_get_rx_buf_size(bp, idx);
>> +	if (rx_buf_size < 0)
>> +		return rx_buf_size;
> 
> Does this survive full ring reconfig? IIRC the large changes to the NIC
> config (like changing ring sizes) free and reallocate all rings in bnxt,
> but due to "historic reasons?" they don't go thru the queue ops.

I'll check when I'm back from lpc, but I was coming from an assumption
that the qcfg series was doing it right, and I believe only the restart
path was looking up the set len value. I'll double check.

-- 
Pavel Begunkov