netdev - Re: [PATCH bpf-next V2 1/5] igc: enable and fix RX hash usage by netstack

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Message-ID: <86517b44-b998-a4ac-da13-1f30d5f69975@iogearbox.net>
Date:   Thu, 27 Apr 2023 19:00:43 +0200
From:   Daniel Borkmann <daniel@...earbox.net>
To:     Jesper Dangaard Brouer <jbrouer@...hat.com>, davem@...emloft.net,
        bpf@...r.kernel.org
Cc:     brouer@...hat.com, netdev@...r.kernel.org, martin.lau@...nel.org,
        ast@...nel.org, alexandr.lobakin@...el.com,
        larysa.zaremba@...el.com, xdp-hints@...-project.net,
        John Fastabend <john.fastabend@...il.com>,
        Tony Nguyen <anthony.l.nguyen@...el.com>,
        yoong.siang.song@...el.com, intel-wired-lan@...ts.osuosl.org,
        pabeni@...hat.com, jesse.brandeburg@...el.com,
        Stanislav Fomichev <sdf@...gle.com>, kuba@...nel.org,
        edumazet@...gle.com, hawk@...nel.org,
        Toke Høiland-Jørgensen <toke@...hat.com>
Subject: Re: [PATCH bpf-next V2 1/5] igc: enable and fix RX hash usage by
 netstack

On 4/25/23 10:43 AM, Jesper Dangaard Brouer wrote:
> On 24/04/2023 21.17, John Fastabend wrote:
>>>> Just curious why not copy the logic from the other driver fms10k, ice, ect.
>>>>
>>>>     skb_set_hash(skb, le32_to_cpu(rx_desc->wb.lower.hi_dword.rss),
>>>>              (IXGBE_RSS_L4_TYPES_MASK & (1ul << rss_type)) ?
>>>>              PKT_HASH_TYPE_L4 : PKT_HASH_TYPE_L3);
>>> Detail: This code mis-categorize (e.g. ARP) PKT_HASH_TYPE_L2 as
>>> PKT_HASH_TYPE_L3, but as core reduces this further to one SKB bit, it
>>> doesn't really matter.
>>>
>>>> avoiding the table logic. Do the driver folks care?
>>> The define IXGBE_RSS_L4_TYPES_MASK becomes the "table" logic as a 1-bit
>>> true/false table.  It is a more compact table, let me know if this is
>>> preferred.
>>>
>>> Yes, it is really upto driver maintainer people to decide, what code is
>>> preferred ?
>  >
>> Yeah doesn't matter much to me either way. I was just looking at code
>> compared to ice driver while reviewing.
> 
> My preference is to apply this patchset. We/I can easily followup and
> change this to use the more compact approach later (if someone prefers).

Consistency might help imo and would avoid questions/confusion on /why/
doing it differently for igc vs some of the others.

> I know net-next is "closed", but this patchset was posted prior to the
> close.  Plus, a number of companies are waiting for the XDP-hint for HW
> RX timestamp.  The support for driver stmmac is already in net-next
> (commit e3f9c3e34840 ("net: stmmac: add Rx HWTS metadata to XDP receive
> pkt")). Thus, it would be a help if both igc+stmmac changes land in same
> kernel version, as both drivers are being evaluated by these companies.

Given merge window is open now and net-next closed, it's too late to land
(unless Dave/Jakub thinks otherwise given it touches also driver bits).
I've applied the series to bpf-next right now.

Thanks,
Daniel