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[5.89.201.160]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-42e1ca40945sm34929004f8f.30.2025.12.02.09.32.42 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 02 Dec 2025 09:32:42 -0800 (PST) From: Paolo Valerio To: =?utf-8?Q?Th=C3=A9o?= Lebrun , netdev@vger.kernel.org Cc: Nicolas Ferre , Claudiu Beznea , Andrew Lunn , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Lorenzo Bianconi , Thomas Petazzoni , =?utf-8?Q?Gr=C3=A9gory?= Clement , =?utf-8?Q?Beno=C3=AEt?= Monin Subject: Re: [PATCH RFC net-next 4/6] cadence: macb/gem: add XDP support for gem In-Reply-To: References: <20251119135330.551835-1-pvalerio@redhat.com> <20251119135330.551835-5-pvalerio@redhat.com> Date: Tue, 02 Dec 2025 18:32:41 +0100 Message-ID: <87bjkgzt52.fsf@redhat.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable On 27 Nov 2025 at 03:41:56 PM, Th=C3=A9o Lebrun w= rote: > On Wed Nov 19, 2025 at 2:53 PM CET, Paolo Valerio wrote: >> @@ -1273,6 +1275,7 @@ struct macb_queue { >> struct queue_stats stats; >> struct page_pool *page_pool; >> struct sk_buff *skb; >> + struct xdp_rxq_info xdp_q; >> }; > > Those are always named `xdp_rxq` inside the kernel, we should stick with > the calling convention no? > sure >> diff --git a/drivers/net/ethernet/cadence/macb_main.c b/drivers/net/ethe= rnet/cadence/macb_main.c >> index 5829c1f773dd..53ea1958b8e4 100644 >> --- a/drivers/net/ethernet/cadence/macb_main.c >> +++ b/drivers/net/ethernet/cadence/macb_main.c >> @@ -1344,10 +1344,51 @@ static void discard_partial_frame(struct macb_qu= eue *queue, unsigned int begin, >> */ >> } >>=20=20 >> +static u32 gem_xdp_run(struct macb_queue *queue, struct xdp_buff *xdp, >> + struct net_device *dev) > > Why pass `struct net_device` explicitly? It is in queue->bp->dev. > let's avoid this >> +{ >> + struct bpf_prog *prog; >> + u32 act =3D XDP_PASS; >> + >> + rcu_read_lock(); >> + >> + prog =3D rcu_dereference(queue->bp->prog); >> + if (!prog) >> + goto out; >> + >> + act =3D bpf_prog_run_xdp(prog, xdp); >> + switch (act) { >> + case XDP_PASS: >> + goto out; >> + case XDP_REDIRECT: >> + if (unlikely(xdp_do_redirect(dev, xdp, prog))) { >> + act =3D XDP_DROP; >> + break; >> + } >> + goto out; > > Why the `unlikely()`? > just expecting the err path to be the exception, although this is not consistend with the XDP_TX path. Do you prefer to remove it? >> + default: >> + bpf_warn_invalid_xdp_action(dev, prog, act); >> + fallthrough; >> + case XDP_ABORTED: >> + trace_xdp_exception(dev, prog, act); >> + fallthrough; >> + case XDP_DROP: >> + break; >> + } >> + >> + page_pool_put_full_page(queue->page_pool, >> + virt_to_head_page(xdp->data), true); > > Maybe move that to the XDP_DROP, it is the only `break` in the above > switch statement. It will be used by the default and XDP_ABORTED cases > through fallthrough. We can avoid the out label and its two gotos that > way. > We'd not put to page pool in case the redirect fails or am I missing something? >> static int gem_rx(struct macb_queue *queue, struct napi_struct *napi, >> int budget) >> { >> struct macb *bp =3D queue->bp; >> + bool xdp_flush =3D false; >> unsigned int len; >> unsigned int entry; >> void *data; >> @@ -1356,9 +1397,11 @@ static int gem_rx(struct macb_queue *queue, struc= t napi_struct *napi, >> int count =3D 0; >>=20=20 >> while (count < budget) { >> - u32 ctrl; >> - dma_addr_t addr; >> bool rxused, first_frame; >> + struct xdp_buff xdp; >> + dma_addr_t addr; >> + u32 ctrl; >> + u32 ret; >>=20=20 >> entry =3D macb_rx_ring_wrap(bp, queue->rx_tail); >> desc =3D macb_rx_desc(queue, entry); >> @@ -1403,6 +1446,22 @@ static int gem_rx(struct macb_queue *queue, struc= t napi_struct *napi, >> data_len =3D SKB_WITH_OVERHEAD(bp->rx_buffer_size) - bp->rx_offset; >> } >>=20=20 >> + if (!(ctrl & MACB_BIT(RX_SOF) && ctrl & MACB_BIT(RX_EOF))) >> + goto skip_xdp; >> + >> + xdp_init_buff(&xdp, bp->rx_buffer_size, &queue->xdp_q); >> + xdp_prepare_buff(&xdp, data, bp->rx_offset, len, >> + false); >> + xdp_buff_clear_frags_flag(&xdp); > > You prepare the XDP buffer before checking an XDP program is attached. > Could we avoid this work? We'd move the xdp_buff preparation into > gem_xdp_run(), after the RCU pointer dereference. > ack, makes sense >> -static void gem_create_page_pool(struct macb_queue *queue) >> +static void gem_create_page_pool(struct macb_queue *queue, int qid) >> { >> struct page_pool_params pp_params =3D { >> .order =3D 0, >> .flags =3D PP_FLAG_DMA_MAP | PP_FLAG_DMA_SYNC_DEV, >> .pool_size =3D queue->bp->rx_ring_size, >> .nid =3D NUMA_NO_NODE, >> - .dma_dir =3D DMA_FROM_DEVICE, >> + .dma_dir =3D rcu_access_pointer(queue->bp->prog) >> + ? DMA_BIDIRECTIONAL >> + : DMA_FROM_DEVICE, > > Ah, that is the reason for page_pool_get_dma_dir() calls! > :) >> static int macb_change_mtu(struct net_device *dev, int new_mtu) >> { >> + int frame_size =3D new_mtu + ETH_HLEN + ETH_FCS_LEN + MACB_MAX_PAD; >> + struct macb *bp =3D netdev_priv(dev); >> + struct bpf_prog *prog =3D bp->prog; > > No fancy RCU macro? > right, guess an rcu_access_pointer() call is needed here >> +static int macb_xdp(struct net_device *dev, struct netdev_bpf *xdp) >> +{ >> + struct macb *bp =3D netdev_priv(dev); >> + >> + if (!macb_is_gem(bp)) >> + return 0; > > Returning 0 sounds like a mistake, -EOPNOTSUPP sounds more appropriate. > agreed >> + switch (xdp->command) { >> + case XDP_SETUP_PROG: >> + return gem_xdp_setup(dev, xdp->prog, xdp->extack); >> + default: >> + return -EINVAL; > > Same here: we want -EOPNOTSUPP. Otherwise caller cannot dissociate an > unsupported call from one that is supported but failed. > ack >> + } >> +} >> + >> static void gem_update_stats(struct macb *bp) >> { >> struct macb_queue *queue; >> @@ -4390,6 +4529,7 @@ static const struct net_device_ops macb_netdev_ops= =3D { >> .ndo_hwtstamp_set =3D macb_hwtstamp_set, >> .ndo_hwtstamp_get =3D macb_hwtstamp_get, >> .ndo_setup_tc =3D macb_setup_tc, >> + .ndo_bpf =3D macb_xdp, > > We want it to be "gem_" prefixed as it does not support MACB. > ack > Thanks, > > -- > Th=C3=A9o Lebrun, Bootlin > Embedded Linux and Kernel engineering > https://bootlin.com