netdev - Re: [RFC bpf-next] bpf: devmap: move drop error path to devmpap for XDP

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Date:   Wed, 10 Feb 2021 16:29:02 +0100
From:   Jesper Dangaard Brouer <brouer@...hat.com>
To:     Lorenzo Bianconi <lorenzo@...nel.org>
Cc:     bpf@...r.kernel.org, netdev@...r.kernel.org, davem@...emloft.net,
        kuba@...nel.org, ast@...nel.org, daniel@...earbox.net,
        lorenzo.bianconi@...hat.com, toke@...hat.com,
        Freysteinn.Alfredsson@....se, brouer@...hat.com
Subject: Re: [RFC bpf-next] bpf: devmap: move drop error path to devmpap for
 XDP_REDIRECT


Typo in subject line for devmap.

On Wed, 10 Feb 2021 15:18:14 +0100
Lorenzo Bianconi <lorenzo@...nel.org> wrote:

> Move XDP_REDIRECT error path handling from each XDP ethernet driver to
> devmap code. According to the new APIs, the driver running the
> ndo_xdp_xmit pointer, will break tx loop whenever the hw reports a tx
> error and it will just return to devmap caller the number of successfully
> transmitted frames. It will be devmap responsability to free dropped frames.

I think you should start with explaining the "why change".

Copy pasted from design doc[1]:
 [1] https://github.com/xdp-project/xdp-project/blob/master/areas/core/redesign01_ndo_xdp_xmit.org#why-change

Why change: We want to change the current drop semantics, because it
will allow us to implement better queue overflow handling. This is
working towards the larger goal of a XDP TX queue-hook

> Move each XDP ndo_xdp_xmit capable driver to the new APIs:
> - veth
> - virtio-net
> - mvneta
> - mvpp2
> - socionext
> - amazon ena
> - bnxt
> - freescale (dpaa2, dpaa)
> - xen-frontend
> - qede
> - ice
> - igb
> - ixgbe
> - i40e
> - mlx5
> - ti (cpsw, cpsw-new)
> - tun
> - sfc
> 
> This is a preliminary patch to introduce a XDP_TX queue hook used to
> managed pending frames that has not been transmitted by the hw.
> More details about the new ndo_xdp_xmit design can be found here [0].
> 
> [0] https://github.com/xdp-project/xdp-project/blob/master/areas/core/redesign01_ndo_xdp_xmit.org



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