netdev - Re: [PATCH v2 net-next 0/9] mvneta: introduce XDP multi-buffer support

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Date:   Fri, 4 Sep 2020 09:39:50 +0200
From:   Lorenzo Bianconi <lorenzo@...nel.org>
To:     John Fastabend <john.fastabend@...il.com>
Cc:     netdev@...r.kernel.org, bpf@...r.kernel.org, davem@...emloft.net,
        lorenzo.bianconi@...hat.com, brouer@...hat.com,
        echaudro@...hat.com, sameehj@...zon.com, kuba@...nel.org,
        daniel@...earbox.net, ast@...nel.org, shayagr@...zon.com
Subject: Re: [PATCH v2 net-next 0/9] mvneta: introduce XDP multi-buffer
 support

> Lorenzo Bianconi wrote:
> > - Finalize XDP multi-buffer support for mvneta driver introducing the
> >   capability to map non-linear buffers on tx side.
> > - Introduce multi-buffer bit (mb) in xdp_frame/xdp_buffer to specify if
> >   shared_info area has been properly initialized.
> > - Initialize multi-buffer bit (mb) to 0 in all XDP-capable drivers.
> > - Add multi-buff support to xdp_return_{buff/frame} utility routines.
> > - Introduce bpf_xdp_adjust_mb_header helper to adjust frame headers moving
> >   *offset* bytes from/to the second buffer to/from the first one.
> >   This helper can be used to move headers when the hw DMA SG is not able
> >   to copy all the headers in the first fragment and split header and data
> >   pages. A possible use case for bpf_xdp_adjust_mb_header is described
> >   here [0]
> 
> Are those slides available anywhere? [0] is just a link to the abstract.

Yes, sorry. I would point out where we got the idea for this helper.
I do not think the slides are available yet but I guess they will be soon.

> 
> > - Introduce bpf_xdp_get_frag_count and bpf_xdp_get_frags_total_size helpers to
> >   report the total number/size of frags for a given xdp multi-buff.
> > 
> > XDP multi-buffer design principles are described here [1]
> > For the moment we have not implemented any self-test for the introduced the bpf
> > helpers. We can address this in a follow up series if the proposed approach
> > is accepted.
> 
> Will need to include selftests with series.

Sure, I will add selftests in v3.

Regards,
Lorenzo

> 
> > 
> > Changes since v1:
> > - Fix use-after-free in xdp_return_{buff/frame}
> > - Introduce bpf helpers
> > - Introduce xdp_mb sample program
> > - access skb_shared_info->nr_frags only on the last fragment
> > 
> > Changes since RFC:
> > - squash multi-buffer bit initialization in a single patch
> > - add mvneta non-linear XDP buff support for tx side
> > 
> > [0] https://netdevconf.info/0x14/session.html?talk-the-path-to-tcp-4k-mtu-and-rx-zerocopy
> > [1] https://github.com/xdp-project/xdp-project/blob/master/areas/core/xdp-multi-buffer01-design.org
> > 
> > Lorenzo Bianconi (7):
> >   xdp: introduce mb in xdp_buff/xdp_frame
> >   xdp: initialize xdp_buff mb bit to 0 in all XDP drivers
> >   net: mvneta: update mb bit before passing the xdp buffer to eBPF layer
> >   xdp: add multi-buff support to xdp_return_{buff/frame}
> >   net: mvneta: add multi buffer support to XDP_TX
> >   bpf: helpers: add bpf_xdp_adjust_mb_header helper
> >   net: mvneta: enable jumbo frames for XDP
> > 
> > Sameeh Jubran (2):
> >   bpf: helpers: add multibuffer support
> >   samples/bpf: add bpf program that uses xdp mb helpers
> > 
> >  drivers/net/ethernet/amazon/ena/ena_netdev.c  |   1 +
> >  drivers/net/ethernet/broadcom/bnxt/bnxt_xdp.c |   1 +
> >  .../net/ethernet/cavium/thunder/nicvf_main.c  |   1 +
> >  .../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 +
> >  .../net/ethernet/intel/ixgbevf/ixgbevf_main.c |   1 +
> >  drivers/net/ethernet/marvell/mvneta.c         | 126 ++++++------
> >  .../net/ethernet/marvell/mvpp2/mvpp2_main.c   |   1 +
> >  drivers/net/ethernet/mellanox/mlx4/en_rx.c    |   1 +
> >  .../net/ethernet/mellanox/mlx5/core/en_rx.c   |   1 +
> >  .../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 +
> >  include/net/xdp.h                             |  26 ++-
> >  include/uapi/linux/bpf.h                      |  39 +++-
> >  net/core/dev.c                                |   1 +
> >  net/core/filter.c                             |  93 +++++++++
> >  net/core/xdp.c                                |  40 ++++
> >  samples/bpf/Makefile                          |   3 +
> >  samples/bpf/xdp_mb_kern.c                     |  68 +++++++
> >  samples/bpf/xdp_mb_user.c                     | 182 ++++++++++++++++++
> >  tools/include/uapi/linux/bpf.h                |  40 +++-
> >  32 files changed, 572 insertions(+), 70 deletions(-)
> >  create mode 100644 samples/bpf/xdp_mb_kern.c
> >  create mode 100644 samples/bpf/xdp_mb_user.c
> > 
> > -- 
> > 2.26.2
> > 
> 
> 

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