From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-15.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 39D77C433E6 for ; Wed, 17 Feb 2021 12:03:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0E6E764E57 for ; Wed, 17 Feb 2021 12:03:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232553AbhBQMDb (ORCPT ); Wed, 17 Feb 2021 07:03:31 -0500 Received: from mail-40136.protonmail.ch ([185.70.40.136]:28215 "EHLO mail-40136.protonmail.ch" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232574AbhBQMCe (ORCPT ); Wed, 17 Feb 2021 07:02:34 -0500 Date: Wed, 17 Feb 2021 12:01:46 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=pm.me; s=protonmail; t=1613563312; bh=rD+msxxQv7QdHAN2CCbl57zhJ/ALAb4aGQXqzumABFM=; h=Date:To:From:Cc:Reply-To:Subject:In-Reply-To:References:From; b=PT3LFaRlDYIV38fZI3I77r0E6FRjWTnolRzDMij8v+KHiOlF1PrjH6OD/eTLWIG/r vRO5YwIToJaBCQfuG3D8h85eevr57gs7i+gJp8O7wHlSUu4al7QRs91SMIn077+2EP 4kYtYfHvMHVtcaW4f5bWsWWJ9vPRwjAoSx2Bhkh9/QRN45SuYmKeujZIcUIcvP0bc6 BwMwNEc7+xBMyTU7alJelqBMMVLlanUgXbNCTImULuUCu5gDwKZsHSAH8+Z8/w0PbH RK6FzU95XwQ1b6MFWnLms29T1f6zGNv+w5d0Qr0PbX27GRFMFxtAhAmH3gqAOA6NBc Srtl/5xLIkMfg== To: Daniel Borkmann , Magnus Karlsson From: Alexander Lobakin Cc: "Michael S. Tsirkin" , Jason Wang , "David S. Miller" , Jakub Kicinski , Jonathan Lemon , Alexei Starovoitov , =?utf-8?Q?Bj=C3=B6rn_T=C3=B6pel?= , Jesper Dangaard Brouer , John Fastabend , Andrii Nakryiko , Martin KaFai Lau , Song Liu , Yonghong Song , KP Singh , Paolo Abeni , Eric Dumazet , Xuan Zhuo , Dust Li , Alexander Lobakin , virtualization@lists.linux-foundation.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, bpf@vger.kernel.org Reply-To: Alexander Lobakin Subject: [PATCH v7 bpf-next 5/6] xsk: respect device's headroom and tailroom on generic xmit path Message-ID: <20210217120003.7938-6-alobakin@pm.me> In-Reply-To: <20210217120003.7938-1-alobakin@pm.me> References: <20210217120003.7938-1-alobakin@pm.me> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org xsk_generic_xmit() allocates a new skb and then queues it for xmitting. The size of new skb's headroom is desc->len, so it comes to the driver/device with no reserved headroom and/or tailroom. Lots of drivers need some headroom (and sometimes tailroom) to prepend (and/or append) some headers or data, e.g. CPU tags, device-specific headers/descriptors (LSO, TLS etc.), and if case of no available space skb_cow_head() will reallocate the skb. Reallocations are unwanted on fast-path, especially when it comes to XDP, so generic XSK xmit should reserve the spaces declared in dev->needed_headroom and dev->needed tailroom to avoid them. Note on max(NET_SKB_PAD, L1_CACHE_ALIGN(dev->needed_headroom)): Usually, output functions reserve LL_RESERVED_SPACE(dev), which consists of dev->hard_header_len + dev->needed_headroom, aligned by 16. However, on XSK xmit hard header is already here in the chunk, so hard_header_len is not needed. But it'd still be better to align data up to cacheline, while reserving no less than driver requests for headroom. NET_SKB_PAD here is to double-insure there will be no reallocations even when the driver advertises no needed_headroom, but in fact need it (not so rare case). Fixes: 35fcde7f8deb ("xsk: support for Tx") Signed-off-by: Alexander Lobakin Acked-by: Magnus Karlsson --- net/xdp/xsk.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c index 4faabd1ecfd1..143979ea4165 100644 --- a/net/xdp/xsk.c +++ b/net/xdp/xsk.c @@ -454,12 +454,16 @@ static int xsk_generic_xmit(struct sock *sk) =09struct sk_buff *skb; =09unsigned long flags; =09int err =3D 0; +=09u32 hr, tr; =20 =09mutex_lock(&xs->mutex); =20 =09if (xs->queue_id >=3D xs->dev->real_num_tx_queues) =09=09goto out; =20 +=09hr =3D max(NET_SKB_PAD, L1_CACHE_ALIGN(xs->dev->needed_headroom)); +=09tr =3D xs->dev->needed_tailroom; + =09while (xskq_cons_peek_desc(xs->tx, &desc, xs->pool)) { =09=09char *buffer; =09=09u64 addr; @@ -471,11 +475,13 @@ static int xsk_generic_xmit(struct sock *sk) =09=09} =20 =09=09len =3D desc.len; -=09=09skb =3D sock_alloc_send_skb(sk, len, 1, &err); +=09=09skb =3D sock_alloc_send_skb(sk, hr + len + tr, 1, &err); =09=09if (unlikely(!skb)) =09=09=09goto out; =20 +=09=09skb_reserve(skb, hr); =09=09skb_put(skb, len); + =09=09addr =3D desc.addr; =09=09buffer =3D xsk_buff_raw_get_data(xs->pool, addr); =09=09err =3D skb_store_bits(skb, 0, buffer, len); --=20 2.30.1