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 52AAEC54EAA for ; Mon, 30 Jan 2023 03:43:07 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1pML3e-0002VN-1i; Sun, 29 Jan 2023 22:42:14 -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 1pML3b-0002VB-VR for qemu-devel@nongnu.org; Sun, 29 Jan 2023 22:42:11 -0500 Received: from out199-14.us.a.mail.aliyun.com ([47.90.199.14]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1pML3Y-0004xa-DB for qemu-devel@nongnu.org; Sun, 29 Jan 2023 22:42:11 -0500 X-Alimail-AntiSpam: AC=PASS; BC=-1|-1; BR=01201311R191e4; CH=green; DM=||false|; DS=||; FP=0|-1|-1|-1|0|-1|-1|-1; HT=ay29a033018045176; MF=xuanzhuo@linux.alibaba.com; NM=1; PH=DS; RN=4; SR=0; TI=SMTPD_---0VaMQ9T9_1675050116; Received: from localhost(mailfrom:xuanzhuo@linux.alibaba.com fp:SMTPD_---0VaMQ9T9_1675050116) by smtp.aliyun-inc.com; Mon, 30 Jan 2023 11:41:57 +0800 Message-ID: <1675049912.7650461-1-xuanzhuo@linux.alibaba.com> Subject: Re: [PATCH v1 2/2] virtio-net: virtio_net_flush_tx() check for per-queue reset Date: Mon, 30 Jan 2023 11:38:32 +0800 From: Xuan Zhuo To: Jason Wang Cc: qemu-devel@nongnu.org, "Michael S. Tsirkin" , Alexander Bulekov References: <20230129025150.119972-1-xuanzhuo@linux.alibaba.com> <20230129025150.119972-3-xuanzhuo@linux.alibaba.com> <1674978207.8889825-4-xuanzhuo@linux.alibaba.com> In-Reply-To: Received-SPF: pass client-ip=47.90.199.14; envelope-from=xuanzhuo@linux.alibaba.com; helo=out199-14.us.a.mail.aliyun.com X-Spam_score_int: -98 X-Spam_score: -9.9 X-Spam_bar: --------- X-Spam_report: (-9.9 / 5.0 requ) BAYES_00=-1.9, ENV_AND_HDR_SPF_MATCH=-0.5, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, UNPARSEABLE_RELAY=0.001, USER_IN_DEF_SPF_WL=-7.5 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, 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. 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 > > > > > > > > > >