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=-17.3 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 1C5D0C433ED for ; Wed, 14 Apr 2021 04:02:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id EBDA161176 for ; Wed, 14 Apr 2021 04:02:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229700AbhDNEC1 (ORCPT ); Wed, 14 Apr 2021 00:02:27 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:42611 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229694AbhDNEC0 (ORCPT ); Wed, 14 Apr 2021 00:02:26 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1618372924; 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=cb160dTeZzNNrUQErRypJRQxN1hzmXq4Crw0cmUCkUs=; b=gpK0qZiQ9M8s8y40iN/JfsZQ2VUCdlK6vbd0xPNUL+bw5yDZ2BK87PU7Fm5nu0dH1OHDCP DqUh6AZnRdBCOdLO//psJWvLcRQm7FDCLkTlGusBaXMQG56OEDG0CS+8dBMNKB2mvdKHGw lFkLDZVeUA1bpqsFo/FIkNYSExSDuj0= 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-480-yOknOJ61Pvy4cwWns3ZXuA-1; Wed, 14 Apr 2021 00:01:58 -0400 X-MC-Unique: yOknOJ61Pvy4cwWns3ZXuA-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 3DFA5189C447; Wed, 14 Apr 2021 04:01:56 +0000 (UTC) Received: from wangxiaodeMacBook-Air.local (ovpn-13-196.pek2.redhat.com [10.72.13.196]) by smtp.corp.redhat.com (Postfix) with ESMTP id E9ACE5D6AC; Wed, 14 Apr 2021 04:01:48 +0000 (UTC) Subject: Re: [PATCH net-next v4 08/10] virtio-net: xsk zero copy xmit setup To: Xuan Zhuo , netdev@vger.kernel.org Cc: "Michael S. Tsirkin" , "David S. Miller" , Jakub Kicinski , =?UTF-8?B?QmrDtnJuIFTDtnBlbA==?= , Magnus Karlsson , Jonathan Lemon , Alexei Starovoitov , Daniel Borkmann , Jesper Dangaard Brouer , John Fastabend , virtualization@lists.linux-foundation.org, bpf@vger.kernel.org, "dust . li" References: <20210413031523.73507-1-xuanzhuo@linux.alibaba.com> <20210413031523.73507-9-xuanzhuo@linux.alibaba.com> From: Jason Wang Message-ID: Date: Wed, 14 Apr 2021 12:01:46 +0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:78.0) Gecko/20100101 Thunderbird/78.9.1 MIME-Version: 1.0 In-Reply-To: <20210413031523.73507-9-xuanzhuo@linux.alibaba.com> Content-Type: text/plain; charset=gbk; format=flowed Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org ÔÚ 2021/4/13 ÉÏÎç11:15, Xuan Zhuo дµÀ: > xsk is a high-performance packet receiving and sending technology. > > This patch implements the binding and unbinding operations of xsk and > the virtio-net queue for xsk zero copy xmit. > > The xsk zero copy xmit depends on tx napi. It's better to describe why zero copy depends on tx napi. > So if tx napi is not true, > an error will be reported. And the entire operation is under the > protection of rtnl_lock. > > If xsk is active, it will prevent ethtool from modifying tx napi. > > Signed-off-by: Xuan Zhuo > Reviewed-by: Dust Li > --- > drivers/net/virtio_net.c | 78 +++++++++++++++++++++++++++++++++++++++- > 1 file changed, 77 insertions(+), 1 deletion(-) > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c > index f52a25091322..8242a9e9f17d 100644 > --- a/drivers/net/virtio_net.c > +++ b/drivers/net/virtio_net.c > @@ -22,6 +22,7 @@ > #include > #include > #include > +#include > > static int napi_weight = NAPI_POLL_WEIGHT; > module_param(napi_weight, int, 0444); > @@ -133,6 +134,11 @@ struct send_queue { > struct virtnet_sq_stats stats; > > struct napi_struct napi; > + > + struct { > + /* xsk pool */ This comment is unnecessary since the code explains itself. > + struct xsk_buff_pool __rcu *pool; > + } xsk; > }; > > /* Internal representation of a receive virtqueue */ > @@ -2249,8 +2255,19 @@ static int virtnet_set_coalesce(struct net_device *dev, > if (napi_weight ^ vi->sq[0].napi.weight) { > if (dev->flags & IFF_UP) > return -EBUSY; > - for (i = 0; i < vi->max_queue_pairs; i++) > + for (i = 0; i < vi->max_queue_pairs; i++) { > + /* xsk xmit depend on the tx napi. So if xsk is active, > + * prevent modifications to tx napi. > + */ > + rcu_read_lock(); > + if (rcu_dereference(vi->sq[i].xsk.pool)) { Let's use rtnl_derefernece() then the rcu_read_lock()/unlock() is not needed. > + rcu_read_unlock(); > + continue; > + } > + rcu_read_unlock(); > + > vi->sq[i].napi.weight = napi_weight; > + } > } > > return 0; > @@ -2518,11 +2535,70 @@ static int virtnet_xdp_set(struct net_device *dev, struct bpf_prog *prog, > return err; > } > > +static int virtnet_xsk_pool_enable(struct net_device *dev, > + struct xsk_buff_pool *pool, > + u16 qid) > +{ > + struct virtnet_info *vi = netdev_priv(dev); > + struct send_queue *sq; > + > + if (qid >= vi->curr_queue_pairs) > + return -EINVAL; > + > + sq = &vi->sq[qid]; > + > + /* xsk zerocopy depend on the tx napi. > + * > + * xsk zerocopy xmit is driven by the tx interrupt. When the device is > + * not busy, napi will be called continuously to send data. When the > + * device is busy, wait for the notification interrupt after the > + * hardware has finished processing the data, and continue to send data > + * in napi. > + */ > + if (!sq->napi.weight) > + return -EPERM; > + > + rcu_read_lock(); > + /* Here is already protected by rtnl_lock, so rcu_assign_pointer is > + * safe. > + */ > + rcu_assign_pointer(sq->xsk.pool, pool); > + rcu_read_unlock(); Any reason for the rcu lock here? And don't we need to synchronize rcu here? > + > + return 0; > +} > + > +static int virtnet_xsk_pool_disable(struct net_device *dev, u16 qid) > +{ > + struct virtnet_info *vi = netdev_priv(dev); > + struct send_queue *sq; > + > + if (qid >= vi->curr_queue_pairs) > + return -EINVAL; > + > + sq = &vi->sq[qid]; > + > + /* Here is already protected by rtnl_lock, so rcu_assign_pointer is > + * safe. > + */ > + rcu_assign_pointer(sq->xsk.pool, NULL); > + > + synchronize_net(); /* Sync with the XSK wakeup and with NAPI. */ Let's move the comment above the code. Thanks > + > + return 0; > +} > + > static int virtnet_xdp(struct net_device *dev, struct netdev_bpf *xdp) > { > switch (xdp->command) { > case XDP_SETUP_PROG: > return virtnet_xdp_set(dev, xdp->prog, xdp->extack); > + case XDP_SETUP_XSK_POOL: > + if (xdp->xsk.pool) > + return virtnet_xsk_pool_enable(dev, xdp->xsk.pool, > + xdp->xsk.queue_id); > + else > + return virtnet_xsk_pool_disable(dev, xdp->xsk.queue_id); > default: > return -EINVAL; > }