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
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