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 10E19C54EED for ; Mon, 30 Jan 2023 08:41:04 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1pMPiK-0005Kg-II; Mon, 30 Jan 2023 03:40:32 -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 1pMPiI-0005Jl-Ty for qemu-devel@nongnu.org; Mon, 30 Jan 2023 03:40:30 -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 1pMPiG-0006s9-Um for qemu-devel@nongnu.org; Mon, 30 Jan 2023 03:40:30 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1675068028; 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=bUgClvTxqsc+38Dy7M7xof7bqX2TBAARRzetlANt3QA=; b=Yk0AAVoO8d3bH8+FjAz5XBHpD/k4Z+Y0OfGqMQhAnt/MMLrtFywgP/2rVIgjCnjDUEh1fM v+SRIt4x/FjI3+v3NmqE48+UKgZxNNNQM4ou1aE/5hltNAu9ZMuUzjt8w407TWxGMhf3uI TPmXpDzi4s15A9mjHD+fo/GA4lgfao4= Received: from mail-oi1-f197.google.com (mail-oi1-f197.google.com [209.85.167.197]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_128_GCM_SHA256) id us-mta-284-AEzzRhW1NISCQRskMORuSQ-1; Mon, 30 Jan 2023 03:40:21 -0500 X-MC-Unique: AEzzRhW1NISCQRskMORuSQ-1 Received: by mail-oi1-f197.google.com with SMTP id ex11-20020a056808298b00b003612dac2af8so4952197oib.5 for ; Mon, 30 Jan 2023 00:40:21 -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=bUgClvTxqsc+38Dy7M7xof7bqX2TBAARRzetlANt3QA=; b=7BKkk9cwoqlPdb5X7Z3aQJzCAkvtvgb9ReeYtAVUKhrkUCwNFed/b7clXtQuz0qiXe nXE/fC1e4RO5r+l2R5iMOOLFJAvcLbr3/P/MU0ETtAFqQCogkNPmSCZ0sWSE4VLe1nTS +WEwUvG0mh6iS0fPWPX9XNruFul3Dg6dseEMRY/GYBWPp5FsufseaGe9P9gfG3mc3Wgt QVpMHrLYwkYX4vvEhUixGE/TJL06XUkUjDm5fwgg788PfKn6OKuPOCgBLvGC+g3loYHO sfXH0JcishQDTHqNbdPg/1QkcwCbFDWuAW+oJcYZCdbEiZfUb5AvOtW7YEB7n0diJmvs GQow== X-Gm-Message-State: AFqh2kpliNjKMAIZGqg7lV6qrS8feHCL9SK4U6YonJaNZV1NCzPCz3cQ zN5q9pcI5UGSslnO8ULudHuCdwZpayEqoYMvz+vLOvKxk3yQYsExiRZFN5GXL7RIzoCBqY+2iw4 YzLtmd/iB6oWDhvcwxRs1ytSgTp4p1vM= X-Received: by 2002:a05:6808:b2f:b0:363:a978:6d41 with SMTP id t15-20020a0568080b2f00b00363a9786d41mr2756105oij.280.1675068020348; Mon, 30 Jan 2023 00:40:20 -0800 (PST) X-Google-Smtp-Source: AMrXdXvFsJnWW7Fr095eW73fToH1UXrBmop9ckLEzfEBe/Q3Ay7KGwD4td22e85ge1+9niui2Nea4oHaMPtQEcrS8N8= X-Received: by 2002:a05:6808:b2f:b0:363:a978:6d41 with SMTP id t15-20020a0568080b2f00b00363a9786d41mr2756102oij.280.1675068020057; Mon, 30 Jan 2023 00:40:20 -0800 (PST) MIME-Version: 1.0 References: <20230129025150.119972-1-xuanzhuo@linux.alibaba.com> <20230129025150.119972-3-xuanzhuo@linux.alibaba.com> <20230129021402-mutt-send-email-mst@kernel.org> <1674977308.9335406-2-xuanzhuo@linux.alibaba.com> <20230129025950-mutt-send-email-mst@kernel.org> <1674980588.489446-5-xuanzhuo@linux.alibaba.com> <20230129065705-mutt-send-email-mst@kernel.org> <1674993822.7782302-1-xuanzhuo@linux.alibaba.com> <20230129071154-mutt-send-email-mst@kernel.org> <1675044912.9269125-1-xuanzhuo@linux.alibaba.com> <20230130003158-mutt-send-email-mst@kernel.org> <1675065225.6382265-1-xuanzhuo@linux.alibaba.com> In-Reply-To: <1675065225.6382265-1-xuanzhuo@linux.alibaba.com> From: Jason Wang Date: Mon, 30 Jan 2023 16:40:08 +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, Alexander Bulekov , "Michael S. Tsirkin" 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 4:03 PM Xuan Zhuo wrote: > > On Mon, 30 Jan 2023 15:49:36 +0800, Jason Wang wrote: > > On Mon, Jan 30, 2023 at 1:32 PM Michael S. Tsirkin wrote: > > > > > > On Mon, Jan 30, 2023 at 10:15:12AM +0800, Xuan Zhuo wrote: > > > > On Sun, 29 Jan 2023 07:15:47 -0500, "Michael S. Tsirkin" wrote: > > > > > On Sun, Jan 29, 2023 at 08:03:42PM +0800, Xuan Zhuo wrote: > > > > > > On Sun, 29 Jan 2023 06:57:29 -0500, "Michael S. Tsirkin" wrote: > > > > > > > On Sun, Jan 29, 2023 at 04:23:08PM +0800, Xuan Zhuo wrote: > > > > > > > > On Sun, 29 Jan 2023 03:12:12 -0500, "Michael S. Tsirkin" wrote: > > > > > > > > > On Sun, Jan 29, 2023 at 03:28:28PM +0800, Xuan Zhuo wrote: > > > > > > > > > > On Sun, 29 Jan 2023 02:25:43 -0500, "Michael S. Tsirkin" wrote: > > > > > > > > > > > On Sun, Jan 29, 2023 at 10:51:50AM +0800, 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. > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > What does "at this time" mean here? > > > > > > > > > > > Do you in fact mean it's called from flush_or_purge_queued_packets? > > > > > > > > > > > > > > > > > > > > Yes > > > > > > > > > > > > > > > > > > > > virtio_queue_reset > > > > > > > > > > k->queue_reset > > > > > > > > > > virtio_net_queue_reset > > > > > > > > > > flush_or_purge_queued_packets > > > > > > > > > > qemu_flush_or_purge_queued_packets > > > > > > > > > > ..... > > > > > > > > > > (callback) virtio_net_tx_complete > > > > > > > > > > virtio_net_flush_tx <-- here send new packet. We need stop it. > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > Because it is inside the callback, I can't pass information through the stack. I > > > > > > > > > > originally thought it was a general situation, so I wanted to put it in > > > > > > > > > > struct VirtQueue. > > > > > > > > > > > > > > > > > > > > If it is not very suitable, it may be better to put it in VirtIONetQueue. > > > > > > > > > > > > > > > > > > > > Thanks. > > > > > > > > > > > > > > > > > > Hmm maybe. Another idea: isn't virtio_net_tx_complete called > > > > > > > > > with length 0 here? Are there other cases where length is 0? > > > > > > > > > > > > > > > > > > > > > > > > > > > > > What does the call stack look like? > > > > > > > > > > > > > > > > > > > > > > If yes introducing a vq state just so virtio_net_flush_tx > > > > > > > > > > > knows we are in the process of reset would be a bad idea. > > > > > > > > > > > We want something much more local, ideally on stack even ... > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > 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)) { > > > > > > > > > > > > > > > > > > btw this sounds like you are asking it to reset some state. > > > > > > > > > > > > > > > > > > > > > return num_packets; > > > > > > > > > > > > > > > > > > and then > > > > > > > > > > > > > > > > > > ret = virtio_net_flush_tx(q); > > > > > > > > > if (ret >= n->tx_burst) > > > > > > > > > > > > > > > > > > > > > > > > > > > will reschedule automatically won't it? > > > > > > > > > > > > > > > > > > also why check in virtio_net_flush_tx and not virtio_net_tx_complete? > > > > > > > > > > > > > > > > virtio_net_flush_tx may been called by timer. > > > > We stop timer/bh during device reset, do we need to do the same with vq reset? > > > > > > > > > > > > > > > > > > Thanks. > > > > > > > > > > > > > > timer won't run while flush_or_purge_queued_packets is in progress. > > > > > > > > > > > > Is timer not executed during the VMEXIT process? Otherwise, we still have to > > > > > > consider that after the flush_or_purge_queued_packets, this process before the > > > > > > structure is cleared. > > > > > > > > > > > > > > > > > > > > void virtio_queue_reset(VirtIODevice *vdev, uint32_t queue_index) > > > > > { > > > > > VirtioDeviceClass *k = VIRTIO_DEVICE_GET_CLASS(vdev); > > > > > > > > > > if (k->queue_reset) { > > > > > k->queue_reset(vdev, queue_index); > > > > > } > > > > > > > > > > __virtio_queue_reset(vdev, queue_index); > > > > > } > > > > > > > > > > > > > > > No timers do not run between k->queue_reset and __virtio_queue_reset. > > > > > > > > > > > > > > > > Even if it can be processed in virtio_net_tx_complete, is there any good way? > > > > > > This is a callback, it is not convenient to pass the parameters. > > > > > > > > > > > > Thanks > > > > > > > > > > > > > > > How about checking that length is 0? > > > > > > > > > > > > I think that check length is not a good way. This modifys the semantics of 0. > > > > 0 seems to mean "purge" and > > > > > It is > > > > not friendly to the future maintenance. On the other hand, qemu_net_queue_purge() > > > > will pass 0, and this function is called by many places. > > > > That's exactly what we want actually, when do purge we don't need a flush? > > Yes, but I'm not sure. If we stop flush, there will be any other effects. So we did: virtio_net_queue_reset(): nc = qemu_get_subqueue(n->nic, vq2q(queue_index); flush_or_purge_queued_packets(nc); qemu_flush_or_purge_queued_packets(nc->peer, true); // [1] if (qemu_net_queue_flush(nc->incoming_queue)) { .... } else if (purge) { qemu_net_queue_purge(nc->incoming_queue, nc->peer); packet->send_cb() virtio_net_tx_complete() virtio_net_flush_tx() qemu_sendv_packet_async() // [2] } We try to flush the tap's incoming queue and if we fail we will purge in [1]. But the sent_cb() tries to send more packets which could be queued to the tap incoming queue [2]. This breaks the semantic of qemu_flush_or_purge_queued_packets(). > > On the other hand, if we use "0" as a judgment condition, do you mean only the > implementation of the purge in the flush_or_purge_queued_packets()? It should be all the users of qemu_net_queue_purge(). The rest users seems all fine: virtio_net_vhost_status(), if we do flush, it may end up with touching vring during vhost is running. filters: all do a flush before. > > > > > > > > > > > How about we add an api in queue.c to replace the sent_cb callback on queue? > > > > > > > > Thanks. > > > > > OK I guess. Jason? > > > > Not sure, anything different from adding a check in > > virtio_net_tx_complete()? (assuming bh and timer is cancelled or > > deleted). > > We replaced the sent_cb with a function without flush. I meant it won't be different from adding a if (virtio_queue_is_rest()) somewhere in virtio_net_tx_complete()? Thanks > > Thanks. > > > > > > Thanks > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > } > > > > > > > > > > > > > > > > > > > > > > > > -- > > > > > > > > > > > > 2.32.0.3.g01195cf9f > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > >