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=-6.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS 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 646F6C433DF for ; Thu, 14 May 2020 10:51:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 41BB620575 for ; Thu, 14 May 2020 10:51:00 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="K48mMCir" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727124AbgENKvA (ORCPT ); Thu, 14 May 2020 06:51:00 -0400 Received: from us-smtp-2.mimecast.com ([205.139.110.61]:31273 "EHLO us-smtp-delivery-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726179AbgENKu7 (ORCPT ); Thu, 14 May 2020 06:50:59 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1589453457; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=P35P1tB2Ow397ehqgn4RyF1fDnfw1KPzt3vs7aSB/Xo=; b=K48mMCirGAlrqlGQTeZpIQh+3a5F/EZwO6p3Pz7ieTgrXm6UBbFUkQpWfgVioSAZnFNNmB 1EZztxTNMFELUH+pOQy2zl4JDylHwhFlWgTT2REE1+mtKaa8acOSClZ211aTv0snsQBfKu 4QuLA7GGC21ctCpHjxodGH0l3/JUwlc= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-514-FVrpKdT2MZuBUxyXYPEWnw-1; Thu, 14 May 2020 06:50:53 -0400 X-MC-Unique: FVrpKdT2MZuBUxyXYPEWnw-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id ACFA48014D7; Thu, 14 May 2020 10:50:51 +0000 (UTC) Received: from firesoul.localdomain (unknown [10.40.208.32]) by smtp.corp.redhat.com (Postfix) with ESMTP id 764396E718; Thu, 14 May 2020 10:50:45 +0000 (UTC) Received: from [192.168.42.3] (localhost [IPv6:::1]) by firesoul.localdomain (Postfix) with ESMTP id 6D27A300020FC; Thu, 14 May 2020 12:50:44 +0200 (CEST) Subject: [PATCH net-next v4 21/33] virtio_net: add XDP frame size in two code paths From: Jesper Dangaard Brouer To: sameehj@amazon.com Cc: Jesper Dangaard Brouer , netdev@vger.kernel.org, bpf@vger.kernel.org, =?utf-8?q?Toke_H=C3=B8iland-J=C3=B8rgensen?= , Daniel Borkmann , Alexei Starovoitov , "David S. Miller" , John Fastabend , Alexander Duyck , Jeff Kirsher , David Ahern , Ilias Apalodimas , Lorenzo Bianconi , Saeed Mahameed , Tariq Toukan Date: Thu, 14 May 2020 12:50:44 +0200 Message-ID: <158945344436.97035.9445115070189151680.stgit@firesoul> In-Reply-To: <158945314698.97035.5286827951225578467.stgit@firesoul> References: <158945314698.97035.5286827951225578467.stgit@firesoul> User-Agent: StGit/0.19 MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 Sender: bpf-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org The virtio_net driver is running inside the guest-OS. There are two XDP receive code-paths in virtio_net, namely receive_small() and receive_mergeable(). The receive_big() function does not support XDP. In receive_small() the frame size is available in buflen. The buffer backing these frames are allocated in add_recvbuf_small() with same size, except for the headroom, but tailroom have reserved room for skb_shared_info. The headroom is encoded in ctx pointer as a value. In receive_mergeable() the frame size is more dynamic. There are two basic cases: (1) buffer size is based on a exponentially weighted moving average (see DECLARE_EWMA) of packet length. Or (2) in case virtnet_get_headroom() have any headroom then buffer size is PAGE_SIZE. The ctx pointer is this time used for encoding two values; the buffer len "truesize" and headroom. In case (1) if the rx buffer size is underestimated, the packet will have been split over more buffers (num_buf info in virtio_net_hdr_mrg_rxbuf placed in top of buffer area). If that happens the XDP path does a xdp_linearize_page operation. V3: Adjust frame_sz in receive_mergeable() case, spotted by Jason Wang. The code is really hard to follow, so some hints to reviewers. The receive_mergeable() case gets frames that were allocated in add_recvbuf_mergeable() which uses headroom=virtnet_get_headroom(), and 'buf' ptr is advanced this headroom. The headroom can only be 0 or VIRTIO_XDP_HEADROOM, as virtnet_get_headroom is really simple: static unsigned int virtnet_get_headroom(struct virtnet_info *vi) { return vi->xdp_queue_pairs ? VIRTIO_XDP_HEADROOM : 0; } As frame_sz is an offset size from xdp.data_hard_start, reviewers should notice how this is calculated in receive_mergeable(): int offset = buf - page_address(page); [...] data = page_address(xdp_page) + offset; xdp.data_hard_start = data - VIRTIO_XDP_HEADROOM + vi->hdr_len; The calculated offset will always be VIRTIO_XDP_HEADROOM when reaching this code. Thus, xdp.data_hard_start will be page-start address plus vi->hdr_len. Given this xdp.frame_sz need to be reduced with vi->hdr_len size. IMHO a followup patch should cleanup this code to make it easier to maintain and understand, but it is outside the scope of this patchset. Cc: Jason Wang Signed-off-by: Jesper Dangaard Brouer Acked-by: Michael S. Tsirkin Acked-by: Jason Wang --- drivers/net/virtio_net.c | 15 ++++++++++++--- 1 file changed, 12 insertions(+), 3 deletions(-) diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c index 11f722460513..9e1b5d748586 100644 --- a/drivers/net/virtio_net.c +++ b/drivers/net/virtio_net.c @@ -689,6 +689,7 @@ static struct sk_buff *receive_small(struct net_device *dev, xdp.data_end = xdp.data + len; xdp.data_meta = xdp.data; xdp.rxq = &rq->xdp_rxq; + xdp.frame_sz = buflen; orig_data = xdp.data; act = bpf_prog_run_xdp(xdp_prog, &xdp); stats->xdp_packets++; @@ -797,10 +798,11 @@ static struct sk_buff *receive_mergeable(struct net_device *dev, int offset = buf - page_address(page); struct sk_buff *head_skb, *curr_skb; struct bpf_prog *xdp_prog; - unsigned int truesize; + unsigned int truesize = mergeable_ctx_to_truesize(ctx); unsigned int headroom = mergeable_ctx_to_headroom(ctx); - int err; unsigned int metasize = 0; + unsigned int frame_sz; + int err; head_skb = NULL; stats->bytes += len - vi->hdr_len; @@ -821,6 +823,11 @@ static struct sk_buff *receive_mergeable(struct net_device *dev, if (unlikely(hdr->hdr.gso_type)) goto err_xdp; + /* Buffers with headroom use PAGE_SIZE as alloc size, + * see add_recvbuf_mergeable() + get_mergeable_buf_len() + */ + frame_sz = headroom ? PAGE_SIZE : truesize; + /* This happens when rx buffer size is underestimated * or headroom is not enough because of the buffer * was refilled before XDP is set. This should only @@ -834,6 +841,8 @@ static struct sk_buff *receive_mergeable(struct net_device *dev, page, offset, VIRTIO_XDP_HEADROOM, &len); + frame_sz = PAGE_SIZE; + if (!xdp_page) goto err_xdp; offset = VIRTIO_XDP_HEADROOM; @@ -850,6 +859,7 @@ static struct sk_buff *receive_mergeable(struct net_device *dev, xdp.data_end = xdp.data + (len - vi->hdr_len); xdp.data_meta = xdp.data; xdp.rxq = &rq->xdp_rxq; + xdp.frame_sz = frame_sz - vi->hdr_len; act = bpf_prog_run_xdp(xdp_prog, &xdp); stats->xdp_packets++; @@ -924,7 +934,6 @@ static struct sk_buff *receive_mergeable(struct net_device *dev, } rcu_read_unlock(); - truesize = mergeable_ctx_to_truesize(ctx); if (unlikely(len > truesize)) { pr_debug("%s: rx error: len %u exceeds truesize %lu\n", dev->name, len, (unsigned long)ctx);