netdev - Re: [PATCH v5 bpf-next 02/14] xdp: initialize xdp

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Date:   Mon, 7 Dec 2020 22:37:11 +0100
From:   Maciej Fijalkowski <maciej.fijalkowski@...el.com>
To:     Alexander Duyck <alexander.duyck@...il.com>
Cc:     Lorenzo Bianconi <lorenzo@...nel.org>, bpf <bpf@...r.kernel.org>,
        Netdev <netdev@...r.kernel.org>,
        David Miller <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>, shayagr@...zon.com,
        "Jubran, Samih" <sameehj@...zon.com>,
        John Fastabend <john.fastabend@...il.com>, dsahern@...nel.org,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        Eelco Chaudron <echaudro@...hat.com>,
        lorenzo.bianconi@...hat.com, Jason Wang <jasowang@...hat.com>
Subject: Re: [PATCH v5 bpf-next 02/14] xdp: initialize xdp_buff mb bit to 0
 in all XDP drivers

On Mon, Dec 07, 2020 at 01:15:00PM -0800, Alexander Duyck wrote:
> On Mon, Dec 7, 2020 at 8:36 AM Lorenzo Bianconi <lorenzo@...nel.org> wrote:
> >
> > Initialize multi-buffer bit (mb) to 0 in all XDP-capable drivers.
> > This is a preliminary patch to enable xdp multi-buffer support.
> >
> > Signed-off-by: Lorenzo Bianconi <lorenzo@...nel.org>
> 
> I'm really not a fan of this design. Having to update every driver in
> order to initialize a field that was fragmented is a pain. At a
> minimum it seems like it might be time to consider introducing some
> sort of initializer function for this so that you can update things in
> one central place the next time you have to add a new field instead of
> having to update every individual driver that supports XDP. Otherwise
> this isn't going to scale going forward.

Also, a good example of why this might be bothering for us is a fact that
in the meantime the dpaa driver got XDP support and this patch hasn't been
updated to include mb setting in that driver.

> 
> > ---
> >  drivers/net/ethernet/amazon/ena/ena_netdev.c        | 1 +
> >  drivers/net/ethernet/broadcom/bnxt/bnxt_xdp.c       | 1 +
> >  drivers/net/ethernet/cavium/thunder/nicvf_main.c    | 1 +
> >  drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.c    | 1 +
> >  drivers/net/ethernet/intel/i40e/i40e_txrx.c         | 1 +
> >  drivers/net/ethernet/intel/ice/ice_txrx.c           | 1 +
> >  drivers/net/ethernet/intel/ixgbe/ixgbe_main.c       | 1 +
> >  drivers/net/ethernet/intel/ixgbevf/ixgbevf_main.c   | 1 +
> >  drivers/net/ethernet/marvell/mvneta.c               | 1 +
> >  drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c     | 1 +
> >  drivers/net/ethernet/mellanox/mlx4/en_rx.c          | 1 +
> >  drivers/net/ethernet/mellanox/mlx5/core/en_rx.c     | 1 +
> >  drivers/net/ethernet/netronome/nfp/nfp_net_common.c | 1 +
> >  drivers/net/ethernet/qlogic/qede/qede_fp.c          | 1 +
> >  drivers/net/ethernet/sfc/rx.c                       | 1 +
> >  drivers/net/ethernet/socionext/netsec.c             | 1 +
> >  drivers/net/ethernet/ti/cpsw.c                      | 1 +
> >  drivers/net/ethernet/ti/cpsw_new.c                  | 1 +
> >  drivers/net/hyperv/netvsc_bpf.c                     | 1 +
> >  drivers/net/tun.c                                   | 2 ++
> >  drivers/net/veth.c                                  | 1 +
> >  drivers/net/virtio_net.c                            | 2 ++
> >  drivers/net/xen-netfront.c                          | 1 +
> >  net/core/dev.c                                      | 1 +
> >  24 files changed, 26 insertions(+)
> >