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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id E78A7C10F1B for ; Tue, 27 Dec 2022 12:24:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229825AbiL0MYh (ORCPT ); Tue, 27 Dec 2022 07:24:37 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37600 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231972AbiL0MYE (ORCPT ); Tue, 27 Dec 2022 07:24:04 -0500 Received: from out30-56.freemail.mail.aliyun.com (out30-56.freemail.mail.aliyun.com [115.124.30.56]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DB19CDE8B; Tue, 27 Dec 2022 04:20:06 -0800 (PST) X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R701e4;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_---0VYDiVIz_1672143603; Received: from 30.120.189.46(mailfrom:hengqi@linux.alibaba.com fp:SMTPD_---0VYDiVIz_1672143603) by smtp.aliyun-inc.com; Tue, 27 Dec 2022 20:20:04 +0800 Message-ID: <2704f3ad-9477-c9d2-8eca-01a9fa92732a@linux.alibaba.com> Date: Tue, 27 Dec 2022 20:20:01 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:108.0) Gecko/20100101 Thunderbird/108.0 Subject: Re: [PATCH v2 2/9] virtio_net: set up xdp for multi buffer packets To: Jason Wang , netdev@vger.kernel.org, bpf@vger.kernel.org Cc: "Michael S . Tsirkin" , Paolo Abeni , Jakub Kicinski , John Fastabend , "David S . Miller" , Daniel Borkmann , Alexei Starovoitov , Eric Dumazet , Xuan Zhuo References: <20221220141449.115918-1-hengqi@linux.alibaba.com> <20221220141449.115918-3-hengqi@linux.alibaba.com> <82eb2ffc-ce97-0c76-f7bc-8a163968cde7@redhat.com> From: Heng Qi In-Reply-To: <82eb2ffc-ce97-0c76-f7bc-8a163968cde7@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org 在 2022/12/27 下午2:32, Jason Wang 写道: > > 在 2022/12/20 22:14, Heng Qi 写道: >> When the xdp program sets xdp.frags, which means it can process >> multi-buffer packets over larger MTU, so we continue to support xdp. >> But for single-buffer xdp, we should keep checking for MTU. >> >> Signed-off-by: Heng Qi >> Reviewed-by: Xuan Zhuo >> --- >>   drivers/net/virtio_net.c | 4 ++-- >>   1 file changed, 2 insertions(+), 2 deletions(-) >> >> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c >> index 443aa7b8f0ad..c5c4e9db4ed3 100644 >> --- a/drivers/net/virtio_net.c >> +++ b/drivers/net/virtio_net.c >> @@ -3095,8 +3095,8 @@ static int virtnet_xdp_set(struct net_device >> *dev, struct bpf_prog *prog, >>           return -EINVAL; >>       } >>   -    if (dev->mtu > max_sz) { >> -        NL_SET_ERR_MSG_MOD(extack, "MTU too large to enable XDP"); >> +    if (prog && !prog->aux->xdp_has_frags && dev->mtu > max_sz) { > > > Not related to this patch, but I see: > >         unsigned long int max_sz = PAGE_SIZE - sizeof(struct > padded_vnet_hdr); > > Which is suspicious, do we need to count reserved headroom/tailroom as > well? This seems to be suspicious. After loading xdp, the size of the filled avail buffer is (PAGE_SIZE - headroom - tailroom), so the size of the received used buffer, ie MTU, should also be (PAGE_SIZE - headroom - tailroom). Thanks. > > Thanks > > >> +        NL_SET_ERR_MSG_MOD(extack, "MTU too large to enable XDP >> without frags"); >>           netdev_warn(dev, "XDP requires MTU less than %lu\n", max_sz); >>           return -EINVAL; >>       }