netdev - Re: [PATCH v2 bpf 1/5] net: ethtool: add xdp properties flag set

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Date:   Fri, 4 Dec 2020 13:46:18 +0100
From:   Maciej Fijalkowski <maciej.fijalkowski@...el.com>
To:     Toke Høiland-Jørgensen <toke@...hat.com>
Cc:     alardam@...il.com, magnus.karlsson@...el.com,
        bjorn.topel@...el.com, andrii.nakryiko@...il.com, kuba@...nel.org,
        ast@...nel.org, daniel@...earbox.net, netdev@...r.kernel.org,
        davem@...emloft.net, john.fastabend@...il.com, hawk@...nel.org,
        jonathan.lemon@...il.com, bpf@...r.kernel.org,
        jeffrey.t.kirsher@...el.com, maciejromanfijalkowski@...il.com,
        intel-wired-lan@...ts.osuosl.org,
        Marek Majtyka <marekx.majtyka@...el.com>
Subject: Re: [PATCH v2 bpf 1/5] net: ethtool: add xdp properties flag set

On Fri, Dec 04, 2020 at 01:18:31PM +0100, Toke Høiland-Jørgensen wrote:
> alardam@...il.com writes:
> 
> > From: Marek Majtyka <marekx.majtyka@...el.com>
> >
> > Implement support for checking what kind of xdp functionality a netdev
> > supports. Previously, there was no way to do this other than to try
> > to create an AF_XDP socket on the interface or load an XDP program and see
> > if it worked. This commit changes this by adding a new variable which
> > describes all xdp supported functions on pretty detailed level:
> 
> I like the direction this is going! :)
> 
> >  - aborted
> >  - drop
> >  - pass
> >  - tx
> >  - redirect
> 
> Drivers can in principle implement support for the XDP_REDIRECT return
> code (and calling xdp_do_redirect()) without implementing ndo_xdp_xmit()
> for being the *target* of a redirect. While my quick grepping doesn't
> turn up any drivers that do only one of these right now, I think we've
> had examples of it in the past, so it would probably be better to split
> the redirect feature flag in two.
> 
> This would also make it trivial to replace the check in __xdp_enqueue()
> (in devmap.c) from looking at whether the ndo is defined, and just
> checking the flag. It would be great if you could do this as part of
> this series.
> 
> Maybe we could even make the 'redirect target' flag be set automatically
> if a driver implements ndo_xdp_xmit?

+1

> 
> >  - zero copy
> >  - hardware offload.
> >
> > Zerocopy mode requires that redirect xdp operation is implemented
> > in a driver and the driver supports also zero copy mode.
> > Full mode requires that all xdp operation are implemented in the driver.
> > Basic mode is just full mode without redirect operation.
> >
> > Initially, these new flags are disabled for all drivers by default.
> >
> > Signed-off-by: Marek Majtyka <marekx.majtyka@...el.com>
> > ---
> >  .../networking/netdev-xdp-properties.rst      | 42 ++++++++
> >  include/linux/netdevice.h                     |  2 +
> >  include/linux/xdp_properties.h                | 53 +++++++++++
> >  include/net/xdp.h                             | 95 +++++++++++++++++++
> >  include/net/xdp_sock_drv.h                    | 10 ++
> >  include/uapi/linux/ethtool.h                  |  1 +
> >  include/uapi/linux/xdp_properties.h           | 32 +++++++
> >  net/ethtool/common.c                          | 11 +++
> >  net/ethtool/common.h                          |  4 +
> >  net/ethtool/strset.c                          |  5 +
> >  10 files changed, 255 insertions(+)
> >  create mode 100644 Documentation/networking/netdev-xdp-properties.rst
> >  create mode 100644 include/linux/xdp_properties.h
> >  create mode 100644 include/uapi/linux/xdp_properties.h
> >
> > diff --git a/Documentation/networking/netdev-xdp-properties.rst b/Documentation/networking/netdev-xdp-properties.rst
> > new file mode 100644
> > index 000000000000..4a434a1c512b
> > --- /dev/null
> > +++ b/Documentation/networking/netdev-xdp-properties.rst
> > @@ -0,0 +1,42 @@
> > +.. SPDX-License-Identifier: GPL-2.0
> > +
> > +=====================
> > +Netdev XDP properties
> > +=====================
> > +
> > + * XDP PROPERTIES FLAGS
> > +
> > +Following netdev xdp properties flags can be retrieve over netlink ethtool
> > +interface the same way as netdev feature flags. These properties flags are
> > +read only and cannot be change in the runtime.
> > +
> > +
> > +*  XDP_ABORTED
> > +
> > +This property informs if netdev supports xdp aborted action.
> > +
> > +*  XDP_DROP
> > +
> > +This property informs if netdev supports xdp drop action.
> > +
> > +*  XDP_PASS
> > +
> > +This property informs if netdev supports xdp pass action.
> > +
> > +*  XDP_TX
> > +
> > +This property informs if netdev supports xdp tx action.
> > +
> > +*  XDP_REDIRECT
> > +
> > +This property informs if netdev supports xdp redirect action.
> > +It assumes the all beforehand mentioned flags are enabled.
> > +
> > +*  XDP_ZEROCOPY
> > +
> > +This property informs if netdev driver supports xdp zero copy.
> > +It assumes the all beforehand mentioned flags are enabled.
> 
> Nit: I think 'XDP_ZEROCOPY' can lead people to think that this is
> zero-copy support for all XDP operations, which is obviously not the
> case. So maybe 'XDP_SOCK_ZEROCOPY' (and update the description to
> mention AF_XDP sockets explicitly)?

AF_XDP_ZEROCOPY?

> 
> -Toke
>