Re: [PATCH net-next v3 1/3] net: rss: Require indir table size or hash key size to support RSS

[Maxime Chevallier <maxime.chevallier@bootlin.com>]

Hi Jakub,

On 10/7/26 01:33, Jakub Kicinski wrote:
> On Tue, 6 Oct 2026 09:59:29 +0200 Maxime Chevallier wrote:
>>> [Severity: Medium]
>>> rss_get_data_alloc() is shared by RSS_GET, RSS_SET and RSS_CREATE. Does
>>> this drop flow-hash reporting for devices that have ->get_rxfh but report
>>> 0/0 sizes?  
>>
>> Yes it does, that's the intended behaviour here. RSS bits are all optional,
>> but does it make sense to report hashing params when the indirection table
>> is size 0 and key len is 0 ?
> 
> Not sure if there's an implementation in the tree but 
> it's possible to implement poor man's RSS on strict
> power-of-2 queue set with some hashing built into the
> Rx engine, without a key. We'd still want to control
> which fields are hashed in this case.
> 
> In the Netlink API we combine the two so we'd break this?

Hmm I wasn't aware of that :( I guess the safe choice is to check on -EOPNOTSUPP
for .get_rxfh() + 0-len indir table / 0-size key and skip the device during the
dump instead of returning early ?

Maxime