netdev - Re: [PATCH v5 bpf-next 03/14] xdp: add xdp_shared

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Message-ID: <20201221100152.58fa6bd7@carbon>
Date:   Mon, 21 Dec 2020 10:01:52 +0100
From:   Jesper Dangaard Brouer <brouer@...hat.com>
To:     Jamal Hadi Salim <jhs@...atatu.com>
Cc:     Shay Agroskin <shayagr@...zon.com>,
        Lorenzo Bianconi <lorenzo.bianconi@...hat.com>,
        Saeed Mahameed <saeed@...nel.org>,
        Lorenzo Bianconi <lorenzo@...nel.org>, bpf@...r.kernel.org,
        netdev@...r.kernel.org, davem@...emloft.net, kuba@...nel.org,
        ast@...nel.org, daniel@...earbox.net, sameehj@...zon.com,
        john.fastabend@...il.com, dsahern@...nel.org, echaudro@...hat.com,
        jasowang@...hat.com, brouer@...hat.com
Subject: Re: [PATCH v5 bpf-next 03/14] xdp: add xdp_shared_info data
 structure

On Sat, 19 Dec 2020 10:30:57 -0500
Jamal Hadi Salim <jhs@...atatu.com> wrote:

> On 2020-12-19 9:53 a.m., Shay Agroskin wrote:
> > 
> > Lorenzo Bianconi <lorenzo.bianconi@...hat.com> writes:
> >   
> 
> >> for the moment I do not know if this area is used for other purposes.
> >> Do you think there are other use-cases for it?  

Yes, all the same use-cases as SKB have.  I wanted to keep this the
same as skb_shared_info, but Lorenzo choose to take John's advice and
it going in this direction (which is fine, we can always change and
adjust this later).


> Sorry to interject:
> Does it make sense to use it to store arbitrary metadata or a scratchpad
> in this space? Something equivalent to skb->cb which is lacking in
> XDP.

Well, XDP have the data_meta area.  But difficult to rely on because a
lot of driver don't implement it.  And Saeed and I plan to use this
area and populate it with driver info from RX-descriptor.

-- 
Best regards,
  Jesper Dangaard Brouer
  MSc.CS, Principal Kernel Engineer at Red Hat
  LinkedIn: http://www.linkedin.com/in/brouer