netdev - Re: [PATCH net v2 1/1] i40e: Fix the inability to attach XDP program on downed interface

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Date:   Wed, 7 Dec 2022 13:16:14 -0800
From:   Tony Nguyen <anthony.l.nguyen@...el.com>
To:     Saeed Mahameed <saeed@...nel.org>
CC:     <davem@...emloft.net>, <kuba@...nel.org>, <pabeni@...hat.com>,
        <edumazet@...gle.com>,
        Bartosz Staszewski <bartoszx.staszewski@...el.com>,
        <netdev@...r.kernel.org>, <bjorn@...nel.org>,
        <maciej.fijalkowski@...el.com>, <magnus.karlsson@...el.com>,
        <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 v2 1/1] i40e: Fix the inability to attach XDP program
 on downed interface

On 12/7/2022 10:25 AM, Saeed Mahameed wrote:
> On 07 Dec 10:08, Tony Nguyen wrote:
>> From: Bartosz Staszewski <bartoszx.staszewski@...el.com>
>>
>> Whenever trying to load XDP prog on downed interface, function i40e_xdp
>> was passing vsi->rx_buf_len field to i40e_xdp_setup() which was equal 0.
>> i40e_open() calls i40e_vsi_configure_rx() which configures that field,
>> but that only happens when interface is up. When it is down, i40e_open()
>> is not being called, thus vsi->rx_buf_len is not set.
>>
>> Solution for this is calculate buffer length in newly created
>> function - i40e_calculate_vsi_rx_buf_len() that return actual buffer
>> length. Buffer length is being calculated based on the same rules
>> applied previously in i40e_vsi_configure_rx() function.
>>
>> Fixes: 613142b0bb88 ("i40e: Log error for oversized MTU on device")
>> Fixes: 0c8493d90b6b ("i40e: add XDP support for pass and drop actions")
>> Signed-off-by: Bartosz Staszewski <bartoszx.staszewski@...el.com>
>> Signed-off-by: Mateusz Palczewski <mateusz.palczewski@...el.com>
>> Tested-by: Shwetha Nagaraju <Shwetha.nagaraju@...el.com>
>> Reviewed-by: Maciej Fijalkowski <maciej.fijalkowski@...el.com>
>> Signed-off-by: Tony Nguyen <anthony.l.nguyen@...el.com>
>> ---
>> v2:
>> - Change title and rework commit message
>> - Dropped, previous, patch 1
>>
>> v1: 
>> https://lore.kernel.org/netdev/20221115000324.3040207-1-anthony.l.nguyen@intel.com/
>>
>> drivers/net/ethernet/intel/i40e/i40e_main.c | 42 +++++++++++++++------
>> 1 file changed, 30 insertions(+), 12 deletions(-)
>>
>> diff --git a/drivers/net/ethernet/intel/i40e/i40e_main.c 
>> b/drivers/net/ethernet/intel/i40e/i40e_main.c
>> index 6416322d7c18..b8a8098110eb 100644
>> --- a/drivers/net/ethernet/intel/i40e/i40e_main.c
>> +++ b/drivers/net/ethernet/intel/i40e/i40e_main.c
>> @@ -3693,6 +3693,30 @@ static int i40e_vsi_configure_tx(struct 
>> i40e_vsi *vsi)
>>     return err;
>> }
>>
>> +/**
>> + * i40e_calculate_vsi_rx_buf_len - Calculates buffer length
>> + *
>> + * @vsi: VSI to calculate rx_buf_len from
>> + */
>> +static u16 i40e_calculate_vsi_rx_buf_len(struct i40e_vsi *vsi)
>> +{
>> +    u16 ret;
>> +
>> +    if (!vsi->netdev || (vsi->back->flags & I40E_FLAG_LEGACY_RX)) {
>> +        ret = I40E_RXBUFFER_2048;
>> +#if (PAGE_SIZE < 8192)
>> +    } else if (!I40E_2K_TOO_SMALL_WITH_PADDING &&
>> +           (vsi->netdev->mtu <= ETH_DATA_LEN)) {
>> +        ret = I40E_RXBUFFER_1536 - NET_IP_ALIGN;
>> +#endif
>> +    } else {
>> +        ret = (PAGE_SIZE < 8192) ? I40E_RXBUFFER_3072 :
>> +                       I40E_RXBUFFER_2048;
>> +    }
>> +
>> +    return ret;
>> +}
> 
> nit: linux coding style states:
> "Do not unnecessarily use braces where a single statement will do"
> 
> I think this applies here.
> 
> Also you could simplify this function to do early returns and drop the u16
> ret variable and all the else statements.
> 
> if (condition 1)
>      return val1;
> 
> if (condition 2)
>      return val2;
> 
> return val3;
> 
> 
> Other than that LGTM.

Thanks for the review. Will make these adjustments in next version.