From: "Toke Høiland-Jørgensen" <toke@redhat.com>
To: Vladimir Oltean <olteanv@gmail.com>
Cc: Jakub Kicinski <kuba@kernel.org>,
Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Jesper Dangaard Brouer <hawk@kernel.org>,
John Fastabend <john.fastabend@gmail.com>,
Andrii Nakryiko <andrii@kernel.org>,
Martin KaFai Lau <kafai@fb.com>, Song Liu <songliubraving@fb.com>,
Yonghong Song <yhs@fb.com>, KP Singh <kpsingh@kernel.org>,
"David S. Miller" <davem@davemloft.net>,
netdev@vger.kernel.org, bpf@vger.kernel.org,
Alexander Duyck <alexander.duyck@gmail.com>,
Ioana Ciornei <ioana.ciornei@nxp.com>,
Alex Marginean <alexandru.marginean@nxp.com>,
Claudiu Manoil <claudiu.manoil@nxp.com>,
Ilias Apalodimas <ilias.apalodimas@linaro.org>,
Vladimir Oltean <vladimir.oltean@nxp.com>
Subject: Re: [PATCH net-next 9/9] net: enetc: add support for XDP_REDIRECT
Date: Thu, 01 Apr 2021 13:39:05 +0200 [thread overview]
Message-ID: <875z16nsiu.fsf@toke.dk> (raw)
In-Reply-To: <20210401113133.vzs3uxkp52k2ctla@skbuf>
Vladimir Oltean <olteanv@gmail.com> writes:
> On Thu, Apr 01, 2021 at 01:26:02PM +0200, Toke Høiland-Jørgensen wrote:
>> > +int enetc_xdp_xmit(struct net_device *ndev, int num_frames,
>> > + struct xdp_frame **frames, u32 flags)
>> > +{
>> > + struct enetc_tx_swbd xdp_redirect_arr[ENETC_MAX_SKB_FRAGS] = {0};
>> > + struct enetc_ndev_priv *priv = netdev_priv(ndev);
>> > + struct enetc_bdr *tx_ring;
>> > + int xdp_tx_bd_cnt, i, k;
>> > + int xdp_tx_frm_cnt = 0;
>> > +
>> > + tx_ring = priv->tx_ring[smp_processor_id()];
>>
>> What mechanism guarantees that this won't overflow the array? :)
>
> Which array, the array of TX rings?
Yes.
> You mean that it's possible to receive a TC_SETUP_QDISC_MQPRIO or
> TC_SETUP_QDISC_TAPRIO with num_tc == 1, and we have 2 CPUs?
Not just that, this ndo can be called on arbitrary CPUs after a
redirect. The code just calls through from the XDP receive path so which
CPU it ends up on depends on the RSS+IRQ config of the other device,
which may not even be the same driver; i.e., you have no control over
that... :)
> Well, yeah, I don't know what's the proper way to deal with that. Ideas?
Well the obvious one is just:
tx_ring = priv->tx_ring[smp_processor_id() % num_ring_ids];
and then some kind of locking to deal with multiple CPUs accessing the
same TX ring...
-Toke
next prev parent reply other threads:[~2021-04-01 18:17 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-31 20:08 [PATCH net-next 0/9] XDP for NXP ENETC Vladimir Oltean
2021-03-31 20:08 ` [PATCH net-next 1/9] net: enetc: consume the error RX buffer descriptors in a dedicated function Vladimir Oltean
2021-03-31 20:08 ` [PATCH net-next 2/9] net: enetc: move skb creation into enetc_build_skb Vladimir Oltean
2021-03-31 20:08 ` [PATCH net-next 3/9] net: enetc: add a dedicated is_eof bit in the TX software BD Vladimir Oltean
2021-03-31 20:08 ` [PATCH net-next 4/9] net: enetc: clean the TX software BD on the TX confirmation path Vladimir Oltean
2021-03-31 20:08 ` [PATCH net-next 5/9] net: enetc: move up enetc_reuse_page and enetc_page_reusable Vladimir Oltean
2021-03-31 20:08 ` [PATCH net-next 6/9] net: enetc: add support for XDP_DROP and XDP_PASS Vladimir Oltean
2021-03-31 20:08 ` [PATCH net-next 7/9] net: enetc: add support for XDP_TX Vladimir Oltean
2021-03-31 20:08 ` [PATCH net-next 8/9] net: enetc: increase RX ring default size Vladimir Oltean
2021-03-31 20:08 ` [PATCH net-next 9/9] net: enetc: add support for XDP_REDIRECT Vladimir Oltean
2021-04-01 11:26 ` Toke Høiland-Jørgensen
2021-04-01 11:31 ` Vladimir Oltean
2021-04-01 11:39 ` Toke Høiland-Jørgensen [this message]
2021-04-01 16:09 ` Vladimir Oltean
2021-04-01 18:01 ` Toke Høiland-Jørgensen
2021-04-01 19:38 ` Vladimir Oltean
2021-04-02 10:56 ` Vladimir Oltean
2021-04-03 11:07 ` Toke Høiland-Jørgensen
2021-04-03 12:12 ` Vladimir Oltean
2021-04-06 11:23 ` Toke Høiland-Jørgensen
2021-03-31 22:20 ` [PATCH net-next 0/9] XDP for NXP ENETC patchwork-bot+netdevbpf
2021-03-31 22:55 ` Vladimir Oltean
2021-04-01 11:28 ` Toke Høiland-Jørgensen
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=875z16nsiu.fsf@toke.dk \
--to=toke@redhat.com \
--cc=alexander.duyck@gmail.com \
--cc=alexandru.marginean@nxp.com \
--cc=andrii@kernel.org \
--cc=ast@kernel.org \
--cc=bpf@vger.kernel.org \
--cc=claudiu.manoil@nxp.com \
--cc=daniel@iogearbox.net \
--cc=davem@davemloft.net \
--cc=hawk@kernel.org \
--cc=ilias.apalodimas@linaro.org \
--cc=ioana.ciornei@nxp.com \
--cc=john.fastabend@gmail.com \
--cc=kafai@fb.com \
--cc=kpsingh@kernel.org \
--cc=kuba@kernel.org \
--cc=netdev@vger.kernel.org \
--cc=olteanv@gmail.com \
--cc=songliubraving@fb.com \
--cc=vladimir.oltean@nxp.com \
--cc=yhs@fb.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.