netdev - Re: [PATCH RFC net-next 0/2] XDP multi buffer helpers

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Date:   Tue, 28 Jul 2020 14:54:33 +0200
From:   Lorenzo Bianconi <lorenzo.bianconi@...hat.com>
To:     Maciej Fijalkowski <maciej.fijalkowski@...el.com>
Cc:     sameehj@...zon.com, davem@...emloft.net, netdev@...r.kernel.org,
        dwmw@...zon.com, zorik@...zon.com, matua@...zon.com,
        saeedb@...zon.com, msw@...zon.com, aliguori@...zon.com,
        nafea@...zon.com, gtzalik@...zon.com, netanel@...zon.com,
        alisaidi@...zon.com, benh@...zon.com, akiyano@...zon.com,
        ndagan@...zon.com, ast@...nel.org, daniel@...earbox.net,
        kafai@...com, songliubraving@...com, yhs@...com, andriin@...com,
        john.fastabend@...il.com, kpsingh@...omium.org, kuba@...nel.org,
        hawk@...nel.org, shayagr@...zon.com, lorenzo@...nel.org
Subject: Re: [PATCH RFC net-next 0/2] XDP multi buffer helpers

> On Mon, Jul 27, 2020 at 12:56:51PM +0000, sameehj@...zon.com wrote:
> > From: Sameeh Jubran <sameehj@...zon.com>
> > 
> > This series is based on the series that Lorenzo sent [0].
> 
> What is your final design for multi buffer support in XDP?
> Why don't you provide a single RFC that is fully functional but instead
> you're sending a bunch of separate RFCs?

Hi Maciej,

IMO the buffer layout is defined now (we will use the trailing part of the
"linear" area of the xdp_buff to store references for subsequent buffers like
we already do for skb).
What is not defined yet are the metadata (e.g. number of frames, total length, ..)
we want to pass to the bpf layer. This is the main reason why I sent this series
[1] as RFC, I want to collect feedbacks about this approach. For the moment (at
least in my series) mb in xdp_buff is just used to indicate if this is a
multi-buff xdp_buff.

> 
> IMHO it's a weird strategy. Not sure what others think about.
> 

we did not coordinate, sorry for the noise.

Regards,
Lorenzo

[1] https://patchwork.ozlabs.org/project/netdev/cover/cover.1595503780.git.lorenzo@kernel.org/

> > 
> > This series simply adds new bpf helpers for xdp mb support as well as
> > introduces a sample program that uses them.
> > 
> > [0] - [RFC net-next 00/22] Introduce mb bit in xdp_buff/xdp_frame
> 
> Direct link wouldn't hurt I guess :) Please also include all the previous
> discussions that took place on mailing list around this topic. This will
> make reviewers life easier I suppose. As I asked above, I'm not sure
> what's your final design for this feature.
> 
> > 
> > Sameeh Jubran (2):
> >   xdp: helpers: add multibuffer support
> >   samples/bpf: add bpf program that uses xdp mb helpers
> > 
> >  include/uapi/linux/bpf.h       |  13 +++
> >  net/core/filter.c              |  60 ++++++++++++++
> >  samples/bpf/Makefile           |   3 +
> >  samples/bpf/xdp_mb_kern.c      |  66 ++++++++++++++++
> >  samples/bpf/xdp_mb_user.c      | 174 +++++++++++++++++++++++++++++++++++++++++
> >  tools/include/uapi/linux/bpf.h |  13 +++
> >  6 files changed, 329 insertions(+)
> >  create mode 100644 samples/bpf/xdp_mb_kern.c
> >  create mode 100644 samples/bpf/xdp_mb_user.c
> > 
> > -- 
> > 2.16.6
> > 
> 

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