From: Daniel Borkmann <daniel@iogearbox•net>
To: Tom Herbert <tom@herbertland•com>, Brenden Blanco <bblanco@plumgrid•com>
Cc: "David S. Miller" <davem@davemloft•net>,
Linux Kernel Network Developers <netdev@vger•kernel.org>,
Jamal Hadi Salim <jhs@mojatatu•com>,
Saeed Mahameed <saeedm@dev•mellanox.co.il>,
Martin KaFai Lau <kafai@fb•com>,
Jesper Dangaard Brouer <brouer@redhat•com>,
Ari Saha <as754m@att•com>,
Alexei Starovoitov <alexei.starovoitov@gmail•com>,
Or Gerlitz <gerlitz.or@gmail•com>,
john fastabend <john.fastabend@gmail•com>,
Hannes Frederic Sowa <hannes@stressinduktion•org>,
Thomas Graf <tgraf@suug•ch>,
Tariq Toukan <ttoukan.linux@gmail•com>
Subject: Re: [PATCH v10 05/12] net/mlx4_en: add support for fast rx drop bpf program
Date: Sun, 24 Jul 2016 22:34:38 +0200 [thread overview]
Message-ID: <5795265E.5000704@iogearbox.net> (raw)
In-Reply-To: <CALx6S37TR90Af=-n=d0sfxxf_SvtwjRjyf_sds-Ne0UZn9i+AA@mail.gmail.com>
On 07/24/2016 06:57 PM, Tom Herbert wrote:
> On Tue, Jul 19, 2016 at 2:16 PM, Brenden Blanco <bblanco@plumgrid•com> wrote:
>> Add support for the BPF_PROG_TYPE_XDP hook in mlx4 driver.
>>
>> In tc/socket bpf programs, helpers linearize skb fragments as needed
>> when the program touches the packet data. However, in the pursuit of
>> speed, XDP programs will not be allowed to use these slower functions,
>> especially if it involves allocating an skb.
>>
>> Therefore, disallow MTU settings that would produce a multi-fragment
>> packet that XDP programs would fail to access. Future enhancements could
>> be done to increase the allowable MTU.
>>
>> The xdp program is present as a per-ring data structure, but as of yet
>> it is not possible to set at that granularity through any ndo.
>>
>> Signed-off-by: Brenden Blanco <bblanco@plumgrid•com>
[...]
>> + if (prog) {
>> + prog = bpf_prog_add(prog, priv->rx_ring_num - 1);
>> + if (IS_ERR(prog))
>> + return PTR_ERR(prog);
>> + }
>> +
>> + priv->xdp_ring_num = xdp_ring_num;
>> +
>> + /* This xchg is paired with READ_ONCE in the fast path */
>> + for (i = 0; i < priv->rx_ring_num; i++) {
>> + old_prog = xchg(&priv->rx_ring[i]->xdp_prog, prog);
>
> This can be done under a lock instead of relying on xchg.
>
>> + if (old_prog)
>> + bpf_prog_put(old_prog);
>
> I don't see how this can work. Even after setting the new program, the
> old program might still be run (pointer dereferenced before xchg).
> Either rcu needs to be used or the queue should stopped and synced
> before setting the new program.
It's a strict requirement that all BPF programs must run under RCU.
next prev parent reply other threads:[~2016-07-24 20:34 UTC|newest]
Thread overview: 55+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-07-19 19:16 [PATCH v10 00/12] Add driver bpf hook for early packet drop and forwarding Brenden Blanco
2016-07-19 19:16 ` [PATCH v10 01/12] bpf: add bpf_prog_add api for bulk prog refcnt Brenden Blanco
2016-07-19 21:46 ` Alexei Starovoitov
2016-07-19 19:16 ` [PATCH v10 02/12] bpf: add XDP prog type for early driver filter Brenden Blanco
2016-07-19 21:33 ` Alexei Starovoitov
2016-07-19 19:16 ` [PATCH v10 03/12] net: add ndo to setup/query xdp prog in adapter rx Brenden Blanco
2016-07-19 19:16 ` [PATCH v10 04/12] rtnl: add option for setting link xdp prog Brenden Blanco
2016-07-20 8:38 ` Daniel Borkmann
2016-07-20 17:35 ` Brenden Blanco
2016-07-19 19:16 ` [PATCH v10 05/12] net/mlx4_en: add support for fast rx drop bpf program Brenden Blanco
2016-07-19 21:41 ` Alexei Starovoitov
2016-07-20 9:07 ` Daniel Borkmann
2016-07-20 17:33 ` Brenden Blanco
2016-07-24 11:56 ` Jesper Dangaard Brouer
2016-07-24 16:57 ` Tom Herbert
2016-07-24 20:34 ` Daniel Borkmann [this message]
2016-07-19 19:16 ` [PATCH v10 06/12] Add sample for adding simple drop program to link Brenden Blanco
2016-07-19 21:44 ` Alexei Starovoitov
2016-07-19 19:16 ` [PATCH v10 07/12] net/mlx4_en: add page recycle to prepare rx ring for tx support Brenden Blanco
2016-07-19 21:49 ` Alexei Starovoitov
2016-07-25 7:35 ` Eric Dumazet
2016-08-03 17:45 ` order-0 vs order-N driver allocation. Was: " Alexei Starovoitov
2016-08-04 16:19 ` Jesper Dangaard Brouer
2016-08-05 0:30 ` Alexander Duyck
2016-08-05 3:55 ` Alexei Starovoitov
2016-08-05 15:15 ` Alexander Duyck
2016-08-05 15:33 ` David Laight
2016-08-05 16:00 ` Alexander Duyck
2016-08-05 7:15 ` Eric Dumazet
2016-08-08 2:15 ` Alexei Starovoitov
2016-08-08 8:01 ` Jesper Dangaard Brouer
2016-08-08 18:34 ` Alexei Starovoitov
2016-08-09 12:14 ` Jesper Dangaard Brouer
2016-07-19 19:16 ` [PATCH v10 08/12] bpf: add XDP_TX xdp_action for direct forwarding Brenden Blanco
2016-07-19 21:53 ` Alexei Starovoitov
2016-07-19 19:16 ` [PATCH v10 09/12] net/mlx4_en: break out tx_desc write into separate function Brenden Blanco
2016-07-19 19:16 ` [PATCH v10 10/12] net/mlx4_en: add xdp forwarding and data write support Brenden Blanco
2016-07-19 19:16 ` [PATCH v10 11/12] bpf: enable direct packet data write for xdp progs Brenden Blanco
2016-07-19 21:59 ` Alexei Starovoitov
2016-07-19 19:16 ` [PATCH v10 12/12] bpf: add sample for xdp forwarding and rewrite Brenden Blanco
2016-07-19 22:05 ` Alexei Starovoitov
2016-07-20 17:38 ` Brenden Blanco
2016-07-27 18:25 ` Jesper Dangaard Brouer
2016-08-03 17:01 ` Tom Herbert
2016-08-03 17:11 ` Alexei Starovoitov
2016-08-03 17:29 ` Tom Herbert
2016-08-03 18:29 ` David Miller
2016-08-03 18:29 ` Brenden Blanco
2016-08-03 18:31 ` David Miller
2016-08-03 19:06 ` Tom Herbert
2016-08-03 22:36 ` Alexei Starovoitov
2016-08-03 23:18 ` Daniel Borkmann
2016-07-20 5:09 ` [PATCH v10 00/12] Add driver bpf hook for early packet drop and forwarding David Miller
[not found] ` <6a09ce5d-f902-a576-e44e-8e1e111ae26b@gmail.com>
2016-07-20 14:08 ` Brenden Blanco
2016-07-20 19:14 ` David Miller
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