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 lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id DF65EC54EAA for ; Mon, 30 Jan 2023 03:54:15 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1pMLEg-0004AT-SM; Sun, 29 Jan 2023 22:53:38 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1pMLEf-0004AC-BF for qemu-devel@nongnu.org; Sun, 29 Jan 2023 22:53:37 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1pMLEd-0006Z4-Dv for qemu-devel@nongnu.org; Sun, 29 Jan 2023 22:53:37 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1675050812; 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: in-reply-to:in-reply-to:references:references; bh=8hZPauyqVYtO/kuB19FlaBHHi216A/07JqGTaIDA+JU=; b=OQt8wcw2Efvdvk5L41EQzJDsUgkiEBJyooDHt3B6XOmGEA7W/7tEGB+fPgB4TMW5KivUpF 4HiJvZXzZ3NE3Le2dLDYFjsRDQlTNzLsTz1C28eEArLHuWCJKCErzuf3PpFyOYm5RS/6jd vKai2kUFesq1Y2O9MiYydYf8NkpGtVU= Received: from mail-ot1-f69.google.com (mail-ot1-f69.google.com [209.85.210.69]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_128_GCM_SHA256) id us-mta-278-MbFXhypdM-248wf7ziIBJw-1; Sun, 29 Jan 2023 22:53:30 -0500 X-MC-Unique: MbFXhypdM-248wf7ziIBJw-1 Received: by mail-ot1-f69.google.com with SMTP id m47-20020a05683026ef00b0068bbc172013so2237693otu.12 for ; Sun, 29 Jan 2023 19:53:30 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=8hZPauyqVYtO/kuB19FlaBHHi216A/07JqGTaIDA+JU=; b=cGE/g+xNvSgbG7fgMwsOxwIHXv7V0I4Dsa5ZkWNEOqSoogbz2WgUog+FMlD4PVk+tF BoQALlWDkhHY2bvqG/IzLFhGTW9RRMq14Dkz8zbj7k2K9iIgnxhkouJ0Vt3G6tykOXY8 92yXmkDvaLUdGzFPTMmp14ejNe34+wN1pGu5J2+XVHDdugM4PxU4YP3QNZ3/Mdp7DFE2 cYR7JEqy9FJCPUDh8PAgDZD3OTn1VIH46aZUP5QT8uKikl3Fl2eRHNJm9cYnx6REIKMz F8PX/f4TF6EMyeV53H4MwLJFRZGL2KgSjw2WcFc6dFbx1ufNDba3bsswLC5cfe03dBhd kNbw== X-Gm-Message-State: AFqh2ko0qoecj+k2pfATMPkhoRdiaiiHcVlhGIuRnzOlrXIFEuPdWxhR lu1K92w2+WI4cxleAojK7cDIe6l013iT673aEtlcHK2Kqfwc1jzXk3AZN147HFk9Kflyz07ckKQ 5Pwua2zHCMUN2ztddQ5JH1EQTPZuxFpU= X-Received: by 2002:a05:6808:b2f:b0:363:a978:6d41 with SMTP id t15-20020a0568080b2f00b00363a9786d41mr2715343oij.280.1675050809994; Sun, 29 Jan 2023 19:53:29 -0800 (PST) X-Google-Smtp-Source: AMrXdXtXbuy85xNxlmpJp58kfkT8zNWuiXHubZ2bQ786hGLf5AWwcOYH1DKd5KopJM9gWqFCFVH2WRdthIoXEOOOKbo= X-Received: by 2002:a05:6808:b2f:b0:363:a978:6d41 with SMTP id t15-20020a0568080b2f00b00363a9786d41mr2715341oij.280.1675050809701; Sun, 29 Jan 2023 19:53:29 -0800 (PST) MIME-Version: 1.0 References: <20230129025150.119972-1-xuanzhuo@linux.alibaba.com> <20230129025150.119972-3-xuanzhuo@linux.alibaba.com> <1674978207.8889825-4-xuanzhuo@linux.alibaba.com> <1675049912.7650461-1-xuanzhuo@linux.alibaba.com> In-Reply-To: <1675049912.7650461-1-xuanzhuo@linux.alibaba.com> From: Jason Wang Date: Mon, 30 Jan 2023 11:53:18 +0800 Message-ID: Subject: Re: [PATCH v1 2/2] virtio-net: virtio_net_flush_tx() check for per-queue reset To: Xuan Zhuo Cc: qemu-devel@nongnu.org, "Michael S. Tsirkin" , Alexander Bulekov Content-Type: text/plain; charset="UTF-8" Received-SPF: pass client-ip=170.10.133.124; envelope-from=jasowang@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Mon, Jan 30, 2023 at 11:42 AM Xuan Zhuo wrote: > > On Mon, 30 Jan 2023 11:01:40 +0800, Jason Wang wrote: > > On Sun, Jan 29, 2023 at 3:44 PM Xuan Zhuo wrote: > > > > > > On Sun, 29 Jan 2023 14:23:21 +0800, Jason Wang wrote: > > > > On Sun, Jan 29, 2023 at 10:52 AM Xuan Zhuo wrote: > > > > > > > > > > Check whether it is per-queue reset state in virtio_net_flush_tx(). > > > > > > > > > > Before per-queue reset, we need to recover async tx resources. At this > > > > > time, virtio_net_flush_tx() is called, but we should not try to send > > > > > new packets, so virtio_net_flush_tx() should check the current > > > > > per-queue reset state. > > > > > > > > > > Fixes: 7dc6be52 ("virtio-net: support queue reset") > > > > > Fixes: https://gitlab.com/qemu-project/qemu/-/issues/1451 > > > > > Reported-by: Alexander Bulekov > > > > > Signed-off-by: Xuan Zhuo > > > > > --- > > > > > hw/net/virtio-net.c | 3 ++- > > > > > 1 file changed, 2 insertions(+), 1 deletion(-) > > > > > > > > > > diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c > > > > > index 3ae909041a..fba6451a50 100644 > > > > > --- a/hw/net/virtio-net.c > > > > > +++ b/hw/net/virtio-net.c > > > > > @@ -2627,7 +2627,8 @@ static int32_t virtio_net_flush_tx(VirtIONetQueue *q) > > > > > VirtQueueElement *elem; > > > > > int32_t num_packets = 0; > > > > > int queue_index = vq2q(virtio_get_queue_index(q->tx_vq)); > > > > > - if (!(vdev->status & VIRTIO_CONFIG_S_DRIVER_OK)) { > > > > > + if (!(vdev->status & VIRTIO_CONFIG_S_DRIVER_OK) || > > > > > + virtio_queue_reset_state(q->tx_vq)) { > > > > > > > > We have other places that check DRIVER_OK do we need to check queue > > > > reset as well? > > > > > > I checked it again. I still think that the location of other checking DRIVER_OK > > > does not need to check the queue reset. > > > > For example, if we don't disable can_receive() when the queue is > > reset, it means rx may go for virtio_net_receive_rcu(). It means the > > Qemu is still trying to process the traffic from the network backend > > like tap which may waste cpu cycles. > > > > I think the correct way is to return false when the queue is reset in > > can_receive(), then the backend poll will be disabled (e.g TAP). When > > the queue is enabled again, qemu_flush_queued_packets() will wake up > > the backend polling. > > > > Having had time to check other places but it would be better to > > mention why it doesn't need a check in the changelog. > > > static bool virtio_net_can_receive(NetClientState *nc) > { > VirtIONet *n = qemu_get_nic_opaque(nc); > VirtIODevice *vdev = VIRTIO_DEVICE(n); > VirtIONetQueue *q = virtio_net_get_subqueue(nc); > > if (!vdev->vm_running) { > return false; > } > > if (nc->queue_index >= n->curr_queue_pairs) { > return false; > } > > if (!virtio_queue_ready(q->rx_vq) || > !(vdev->status & VIRTIO_CONFIG_S_DRIVER_OK)) { > return false; > } > > return true; > } > > int virtio_queue_ready(VirtQueue *vq) > { > return vq->vring.avail != 0; > } > > > static void __virtio_queue_reset(VirtIODevice *vdev, uint32_t i) > { > vdev->vq[i].vring.desc = 0; > vdev->vq[i].vring.avail = 0; > vdev->vq[i].vring.used = 0; > vdev->vq[i].last_avail_idx = 0; > vdev->vq[i].shadow_avail_idx = 0; > vdev->vq[i].used_idx = 0; > vdev->vq[i].last_avail_wrap_counter = true; > vdev->vq[i].shadow_avail_wrap_counter = true; > vdev->vq[i].used_wrap_counter = true; > virtio_queue_set_vector(vdev, i, VIRTIO_NO_VECTOR); > vdev->vq[i].signalled_used = 0; > vdev->vq[i].signalled_used_valid = false; > vdev->vq[i].notification = true; > vdev->vq[i].vring.num = vdev->vq[i].vring.num_default; > vdev->vq[i].inuse = 0; > virtio_virtqueue_reset_region_cache(&vdev->vq[i]); > } > > In the implementation of Per-Queue Reset, for RX, we stop RX by setting vdev->vq[i].vring.avail to 0. Ok, but this is kind of fragile (especially when vIOMMU is enabled). I'd add an explicit check for reset there. (probably on top). Thanks > Then callback can_receive will return False. > > > Thanks. > > > > > > Thanks > > > > > > > > Thanks. > > > > > > > > > > > > > > E.g: > > > > virtio_net_can_receive() > > > > virtio_net_tx_{timer|bh}() > > > > > > > > Thanks > > > > > > > > > return num_packets; > > > > > } > > > > > > > > > > -- > > > > > 2.32.0.3.g01195cf9f > > > > > > > > > > > > > > >