Re: [PATCH] bpf: cpumap: report Rx queue index to xdp_rxq_info

From: Toke Høiland-Jørgensen
Date: Tue Jun 10 2025 - 16:25:01 EST


Ujwal Kundur <ujwal.kundur@xxxxxxxxx> writes:

>> This looks wrong...
>> I think this will always return index 0
>
>> So passing dev->_rx to that function will always return 0; which is what
>> the field is already initialised to...
>
> I didn't realize that would always return 0, sorry I should've tried
> to understand that statement better.
>
>> I'll just add that you may want to take a look at Lorenzo's series[0].
>> Rx queue index is sorta HW hint, so it shouldn't be a problem to add the
>> corresponding field to xdp_rx_meta.
>> Then, you can expand cpumap's code to try reading that HW meta if present.
>
> Thank you! I also tried to work backwards to figure out how the
> queue_index would be used if present in xdp_rxq_info but that wasn't
> immediately apparent to me.
> I'm keen on learning/contributing to the BPF part of the network stack
> and this seemed like a good first patch to take up -- I'll understand
> this better and try again.

Sounds good! Don't be discouraged by having to try again, that's
perfectly normal :)

-Toke