netdev - Re: [PATCH bpf-next 10/11] i40e: implement AF

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: <20180605144347.34351ecc@redhat.com>
Date:   Tue, 5 Jun 2018 14:43:47 +0200
From:   Jesper Dangaard Brouer <brouer@...hat.com>
To:     Björn Töpel <bjorn.topel@...il.com>
Cc:     magnus.karlsson@...el.com, magnus.karlsson@...il.com,
        alexander.h.duyck@...el.com, alexander.duyck@...il.com, ast@...com,
        daniel@...earbox.net, netdev@...r.kernel.org,
        mykyta.iziumtsev@...aro.org, john.fastabend@...il.com,
        willemdebruijn.kernel@...il.com, mst@...hat.com,
        michael.lundkvist@...csson.com, jesse.brandeburg@...el.com,
        anjali.singhai@...el.com, qi.z.zhang@...el.com,
        francois.ozog@...aro.org, ilias.apalodimas@...aro.org,
        brian.brooks@...aro.org, andy@...yhouse.net,
        michael.chan@...adcom.com, intel-wired-lan@...ts.osuosl.org,
        brouer@...hat.com
Subject: Re: [PATCH bpf-next 10/11] i40e: implement AF_XDP zero-copy support
 for Tx

On Mon,  4 Jun 2018 14:06:00 +0200
Björn Töpel <bjorn.topel@...il.com> wrote:

> Here, ndo_xsk_async_xmit is implemented. As a shortcut, the existing
> XDP Tx rings are used for zero-copy. This will result in other devices
> doing XDP_REDIRECT to an AF_XDP enabled queue will have its packets
> dropped.

This behavior is problematic, because XDP Tx rings are smp_processor_id
based, and several RX queues can (via proc smp_affinity settings) be
assigned to the same CPU. Thus, other RX-queues (than the AF_XDP
enabled queue) can experience packet drops.  And other devices doing
redirect through i40e, which happen to run on a CPU which XDP Tx queue
is "hijacked" will see dropped packets.

Any plans to allocate/create a dedicated TX ring per AF_XDP socket?

-- 
Best regards,
  Jesper Dangaard Brouer
  MSc.CS, Principal Kernel Engineer at Red Hat
  LinkedIn: http://www.linkedin.com/in/brouer