From patchwork Sat Jan 14 08:22:21 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Heng Qi X-Patchwork-Id: 13101893 X-Patchwork-Delegate: kuba@kernel.org Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4C36FC678D6 for ; Sat, 14 Jan 2023 08:22:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229454AbjANIWm (ORCPT ); Sat, 14 Jan 2023 03:22:42 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35470 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229786AbjANIWj (ORCPT ); Sat, 14 Jan 2023 03:22:39 -0500 Received: from out30-6.freemail.mail.aliyun.com (out30-6.freemail.mail.aliyun.com [115.124.30.6]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2E562468D; Sat, 14 Jan 2023 00:22:36 -0800 (PST) X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R401e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=ay29a033018045168;MF=hengqi@linux.alibaba.com;NM=1;PH=DS;RN=12;SR=0;TI=SMTPD_---0VZX3LLO_1673684552; Received: from localhost(mailfrom:hengqi@linux.alibaba.com fp:SMTPD_---0VZX3LLO_1673684552) by smtp.aliyun-inc.com; Sat, 14 Jan 2023 16:22:32 +0800 From: Heng Qi To: netdev@vger.kernel.org, bpf@vger.kernel.org Cc: Jason Wang , "Michael S . Tsirkin" , Paolo Abeni , Jakub Kicinski , John Fastabend , "David S . Miller" , Daniel Borkmann , Alexei Starovoitov , Eric Dumazet , Xuan Zhuo Subject: [PATCH net-next v5 02/10] virtio-net: fix calculation of MTU for single-buffer xdp Date: Sat, 14 Jan 2023 16:22:21 +0800 Message-Id: <20230114082229.62143-3-hengqi@linux.alibaba.com> X-Mailer: git-send-email 2.19.1.6.gb485710b In-Reply-To: <20230114082229.62143-1-hengqi@linux.alibaba.com> References: <20230114082229.62143-1-hengqi@linux.alibaba.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org X-Patchwork-Delegate: kuba@kernel.org When single-buffer xdp is loaded, the size of the buffer filled each time is 'sz = (PAGE_SIZE - headroom - tailroom)', which is the maximum packet length that the driver allows the device to pass in. Otherwise, the packet with a length greater than sz will come in, so num_buf will be greater than or equal to 2, and xdp_linearize_page() will be performed and the packet will be dropped because the total length is greater than PAGE_SIZE. So the maximum value of MTU for single-buffer xdp is 'max_sz = sz - ETH_HLEN'. Signed-off-by: Heng Qi Reviewed-by: Xuan Zhuo Acked-by: Jason Wang --- In fact, this is a fix patch belonging to the net branch, which needs to be backported to the stable branch. drivers/net/virtio_net.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c index 443aa7b8f0ad..1203e4176b66 100644 --- a/drivers/net/virtio_net.c +++ b/drivers/net/virtio_net.c @@ -3074,7 +3074,9 @@ static int virtnet_restore_guest_offloads(struct virtnet_info *vi) static int virtnet_xdp_set(struct net_device *dev, struct bpf_prog *prog, struct netlink_ext_ack *extack) { - unsigned long int max_sz = PAGE_SIZE - sizeof(struct padded_vnet_hdr); + unsigned int room = SKB_DATA_ALIGN(VIRTIO_XDP_HEADROOM + + sizeof(struct skb_shared_info)); + unsigned int max_sz = PAGE_SIZE - room - ETH_HLEN; struct virtnet_info *vi = netdev_priv(dev); struct bpf_prog *old_prog; u16 xdp_qp = 0, curr_qp; @@ -3097,7 +3099,7 @@ static int virtnet_xdp_set(struct net_device *dev, struct bpf_prog *prog, if (dev->mtu > max_sz) { NL_SET_ERR_MSG_MOD(extack, "MTU too large to enable XDP"); - netdev_warn(dev, "XDP requires MTU less than %lu\n", max_sz); + netdev_warn(dev, "XDP requires MTU less than %u\n", max_sz); return -EINVAL; }