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 A3CCAC10F1B for ; Tue, 27 Dec 2022 07:52:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230090AbiL0HwJ (ORCPT ); Tue, 27 Dec 2022 02:52:09 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50798 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230057AbiL0HwI (ORCPT ); Tue, 27 Dec 2022 02:52:08 -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 10A755FC4; Mon, 26 Dec 2022 23:52:06 -0800 (PST) X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R351e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=ay29a033018045192;MF=hengqi@linux.alibaba.com;NM=1;PH=DS;RN=12;SR=0;TI=SMTPD_---0VYCu.ol_1672127522; Received: from 30.120.189.46(mailfrom:hengqi@linux.alibaba.com fp:SMTPD_---0VYCu.ol_1672127522) by smtp.aliyun-inc.com; Tue, 27 Dec 2022 15:52:03 +0800 Message-ID: Date: Tue, 27 Dec 2022 15:51:59 +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 7/9] virtio_net: build skb from multi-buffer xdp 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> <20221220141449.115918-8-hengqi@linux.alibaba.com> <9d049351-11c8-2178-c88c-6d4496df773e@redhat.com> From: Heng Qi In-Reply-To: <9d049351-11c8-2178-c88c-6d4496df773e@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3:31, Jason Wang 写道: > > 在 2022/12/20 22:14, Heng Qi 写道: >> This converts the xdp_buff directly to a skb, including >> multi-buffer and single buffer xdp. We'll isolate the >> construction of skb based on xdp from page_to_skb(). >> >> Signed-off-by: Heng Qi >> Reviewed-by: Xuan Zhuo >> --- >>   drivers/net/virtio_net.c | 50 ++++++++++++++++++++++++++++++++++++++++ >>   1 file changed, 50 insertions(+) >> >> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c >> index 9f31bfa7f9a6..4e12196fcfd4 100644 >> --- a/drivers/net/virtio_net.c >> +++ b/drivers/net/virtio_net.c >> @@ -948,6 +948,56 @@ static struct sk_buff *receive_big(struct >> net_device *dev, >>       return NULL; >>   } >>   +/* Why not use xdp_build_skb_from_frame() ? >> + * XDP core assumes that xdp frags are PAGE_SIZE in length, while in >> + * virtio-net there are 2 points that do not match its requirements: >> + *  1. The size of the prefilled buffer is not fixed before xdp is set. >> + *  2. When xdp is loaded, virtio-net has a hole mechanism (refer to >> + *     add_recvbuf_mergeable()), which will make the size of a buffer >> + *     exceed PAGE_SIZE. > > > Is point 2 still valid after patch 1? Yes, it is invalid anymore, I'll correct that, and there's a little more reason that xdp_build_skb_from_frame() does more checks that we don't need, like eth_type_trans() (which virtio-net does in receive_buf()). > > Other than this: > > Acked-by: Jason Wang Thanks for your energy. > > Thanks > > >> + */ >> +static struct sk_buff *build_skb_from_xdp_buff(struct net_device *dev, >> +                           struct virtnet_info *vi, >> +                           struct xdp_buff *xdp, >> +                           unsigned int xdp_frags_truesz) >> +{ >> +    struct skb_shared_info *sinfo = xdp_get_shared_info_from_buff(xdp); >> +    unsigned int headroom, data_len; >> +    struct sk_buff *skb; >> +    int metasize; >> +    u8 nr_frags; >> + >> +    if (unlikely(xdp->data_end > xdp_data_hard_end(xdp))) { >> +        pr_debug("Error building skb as missing reserved tailroom >> for xdp"); >> +        return NULL; >> +    } >> + >> +    if (unlikely(xdp_buff_has_frags(xdp))) >> +        nr_frags = sinfo->nr_frags; >> + >> +    skb = build_skb(xdp->data_hard_start, xdp->frame_sz); >> +    if (unlikely(!skb)) >> +        return NULL; >> + >> +    headroom = xdp->data - xdp->data_hard_start; >> +    data_len = xdp->data_end - xdp->data; >> +    skb_reserve(skb, headroom); >> +    __skb_put(skb, data_len); >> + >> +    metasize = xdp->data - xdp->data_meta; >> +    metasize = metasize > 0 ? metasize : 0; >> +    if (metasize) >> +        skb_metadata_set(skb, metasize); >> + >> +    if (unlikely(xdp_buff_has_frags(xdp))) >> +        xdp_update_skb_shared_info(skb, nr_frags, >> +                       sinfo->xdp_frags_size, >> +                       xdp_frags_truesz, >> +                       xdp_buff_is_frag_pfmemalloc(xdp)); >> + >> +    return skb; >> +} >> + >>   /* TODO: build xdp in big mode */ >>   static int virtnet_build_xdp_buff_mrg(struct net_device *dev, >>                         struct virtnet_info *vi,