netdev - Re: [PATCH net 1/2] i40e: Fix failure message when XDP is configured in TX only mode

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Date:   Wed, 16 Nov 2022 14:29:04 -0800
From:   Saeed Mahameed <saeed@...nel.org>
To:     Maciej Fijalkowski <maciej.fijalkowski@...el.com>
Cc:     Tony Nguyen <anthony.l.nguyen@...el.com>, davem@...emloft.net,
        kuba@...nel.org, pabeni@...hat.com, edumazet@...gle.com,
        Sylwester Dziedziuch <sylwesterx.dziedziuch@...el.com>,
        netdev@...r.kernel.org, magnus.karlsson@...el.com,
        bjorn@...nel.org, ast@...nel.org, daniel@...earbox.net,
        hawk@...nel.org, john.fastabend@...il.com, bpf@...r.kernel.org,
        Mateusz Palczewski <mateusz.palczewski@...el.com>,
        Shwetha Nagaraju <Shwetha.nagaraju@...el.com>
Subject: Re: [PATCH net 1/2] i40e: Fix failure message when XDP is configured
 in TX only mode

On 15 Nov 13:13, Maciej Fijalkowski wrote:
>On Mon, Nov 14, 2022 at 04:03:23PM -0800, Tony Nguyen wrote:
>> From: Sylwester Dziedziuch <sylwesterx.dziedziuch@...el.com>
>>
>> When starting xdpsock program in TX only mode:
>>
>> samples/bpf/xdpsock -i <interface> -t
>>
>> there was an error on i40e driver:
>>
>> Failed to allocate some buffers on AF_XDP ZC enabled Rx ring 0 (pf_q 81)
>>
>> It was caused by trying to allocate RX buffers even though
>> no RX buffers are available because we run in TX only mode.
>>
>> Fix this by checking for number of available buffers
>> for RX queue when allocating buffers during XDP setup.
>
>I was not sure if we want to proceed with this or not. For sure it's not a
>fix to me, behavior was not broken, txonly mode was working correctly.
>We're only getting rid of the bogus message that caused confusion within
>people.
>
>I feel that if we want that in then we should route this via -next and
>address other drivers as well. Not sure what are Magnus' thoughts on this.
>
+1

Some other driver might not have this print message issue, but it would be
nice if the driver got some indication of the TX only nature so maybe we can
cut some corners on napi and avoid even attempting to allocate the rx zc
buffers.