netdev - Re: [RFC v2 bpf-next 3/7] xsk: add usage of XDP features flags

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Message-ID: <51afcd71-8c19-8033-e21a-313b58f196ec@meta.com>
Date:   Tue, 17 Jan 2023 15:37:58 -0800
From:   Yonghong Song <yhs@...a.com>
To:     Lorenzo Bianconi <lorenzo@...nel.org>
Cc:     bpf@...r.kernel.org, netdev@...r.kernel.org, ast@...nel.org,
        daniel@...earbox.net, andrii@...nel.org, davem@...emloft.net,
        kuba@...nel.org, hawk@...nel.org, pabeni@...hat.com,
        edumazet@...gle.com, toke@...hat.com, memxor@...il.com,
        alardam@...il.com, saeedm@...dia.com, anthony.l.nguyen@...el.com,
        gospo@...adcom.com, vladimir.oltean@....com, nbd@....name,
        john@...ozen.org, leon@...nel.org, simon.horman@...igine.com,
        aelior@...vell.com, christophe.jaillet@...adoo.fr,
        ecree.xilinx@...il.com, mst@...hat.com, bjorn@...nel.org,
        magnus.karlsson@...el.com, maciej.fijalkowski@...el.com,
        intel-wired-lan@...ts.osuosl.org, lorenzo.bianconi@...hat.com
Subject: Re: [RFC v2 bpf-next 3/7] xsk: add usage of XDP features flags



On 1/17/23 3:34 PM, Lorenzo Bianconi wrote:
>>
>>
>> On 1/14/23 7:54 AM, Lorenzo Bianconi wrote:
>>> From: Marek Majtyka <alardam@...il.com>
>>>
>>> Change necessary condition check for XSK from ndo functions to
>>> xdp features flags.
>>>
>>> Signed-off-by: Marek Majtyka <alardam@...il.com>
>>> Signed-off-by: Lorenzo Bianconi <lorenzo@...nel.org>
>>> ---
>>>    net/xdp/xsk_buff_pool.c | 3 +--
>>>    1 file changed, 1 insertion(+), 2 deletions(-)
>>>
>>> diff --git a/net/xdp/xsk_buff_pool.c b/net/xdp/xsk_buff_pool.c
>>> index ed6c71826d31..2e6fa082142a 100644
>>> --- a/net/xdp/xsk_buff_pool.c
>>> +++ b/net/xdp/xsk_buff_pool.c
>>> @@ -178,8 +178,7 @@ int xp_assign_dev(struct xsk_buff_pool *pool,
>>>    		/* For copy-mode, we are done. */
>>>    		return 0;
>>> -	if (!netdev->netdev_ops->ndo_bpf ||
>>> -	    !netdev->netdev_ops->ndo_xsk_wakeup) {
>>> +	if ((netdev->xdp_features & NETDEV_XDP_ACT_ZC) != NETDEV_XDP_ACT_ZC) {
>>
>> Maybe:
>> 	if (!(netdev->xdp_features & NETDEV_XDP_ACT_ZC))
> 
> I would say it not equivalent since:
> 
> NETDEV_XDP_ACT_ZC = 0x5f
> 
> and we want the device supports all the ZC requested features. Agree?

I missed the fact that NETDEV_XDP_ACT_ZC is not a BIT(...).
So your implementation is correct, sorry for the noise.

> 
> Regards,
> Lorenzo
> 
>> ?
>>
>>>    		err = -EOPNOTSUPP;
>>>    		goto err_unreg_pool;
>>>    	}