netdev - Re: [PATCH RFC 1/3] xdp: Infrastructure to generalize XDP

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20160921195450.4c5feb4a@jkicinski-Precision-T1700>
Date:   Wed, 21 Sep 2016 19:54:50 +0100
From:   Jakub Kicinski <kubakici@...pl>
To:     Tom Herbert <tom@...bertland.com>
Cc:     Alexei Starovoitov <ast@...com>,
        "David S. Miller" <davem@...emloft.net>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>,
        Kernel Team <kernel-team@...com>,
        Tariq Toukan <tariqt@...lanox.com>,
        Brenden Blanco <bblanco@...mgrid.com>,
        Alexei Starovoitov <alexei.starovoitov@...il.com>,
        Eric Dumazet <eric.dumazet@...il.com>,
        Jesper Dangaard Brouer <brouer@...hat.com>
Subject: Re: [PATCH RFC 1/3] xdp: Infrastructure to generalize XDP

On Wed, 21 Sep 2016 11:50:06 -0700, Tom Herbert wrote:
> On Wed, Sep 21, 2016 at 11:45 AM, Jakub Kicinski <kubakici@...pl> wrote:
> > On Wed, 21 Sep 2016 10:39:40 -0700, Tom Herbert wrote:  
> >> On Wed, Sep 21, 2016 at 10:26 AM, Jakub Kicinski <kubakici@...pl> wrote:  
> >> > On Tue, 20 Sep 2016 17:01:39 -0700, Alexei Starovoitov wrote:  
> >> >>  >  - Reduces the amount of code and complexity needed in drivers to
> >> >>  >    manage XDP  
> >> >>
> >> >> hmm:
> >> >> 534 insertions(+), 144 deletions(-)
> >> >> looks like increase in complexity instead.  
> >> >
> >> > and more to come to tie this with HW offloads.  
> >>
> >> The amount of driver code did decrease with these patches:
> >>
> >> drivers/net/ethernet/mellanox/mlx4/en_netdev.c | 64 ++++----------------------
> >> drivers/net/ethernet/mellanox/mlx4/en_rx.c     | 25 ++++------
> >> drivers/net/ethernet/mellanox/mlx4/mlx4_en.h   |  1 -
> >>
> >> Minimizing complexity being added to drivers for XDP is critical since
> >> we basically asking every driver to replicate the function. This
> >> property also should also apply to HW offloads, the more complexity we
> >> can abstract out drivers into a common backend infrastructure the
> >> better for supporting across different drivers.  
> >
> > I'm in the middle of writing/testing XDP support for the Netronome's
> > driver and generic infra is very much appreciated ;)  In my experience
> > the 50 lines of code which are required for assigning the programs and
> > freeing them aren't really a big deal, though.
> >  
> 
> 50 lines in one driver is not a big deal, 50 lines in a hundred
> drivers is! I learned this lesson in BQL which was well abstracted out
> to be minimally invasive but we still saw many issues because of the
> pecularities of different drivers.

Agreed, I just meant to say that splitting rings and rewritting RX path
to behave differently for XDP vs non-XDP case is way more brain
consuming than a bit of boilerplate code so if anyone could solve those
two it would be much appreciated :)  My main point was what I wrote
below, though.

> > Let's also separate putting xdp_prog in netdevice/napi_struct from the
> > generic hook infra.  All the simplifications to the driver AFAICS come
> > from the former.  If everyone is fine with growing napi_struct we can do
> > that but IMHO this is not an argument for the generic infra :)