From patchwork Thu Oct 20 09:58:45 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Laurent Vivier X-Patchwork-Id: 13013005 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 813C1C4332F for ; Thu, 20 Oct 2022 10:29:23 +0000 (UTC) Received: from localhost ([::1]:49676 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1olSni-0002WB-4O for qemu-devel@archiver.kernel.org; Thu, 20 Oct 2022 06:29:22 -0400 Received: from [::1] (helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1olSb9-00085W-TF for qemu-devel@archiver.kernel.org; Thu, 20 Oct 2022 06:16:24 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:59876) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1olSKM-00024z-2P for qemu-devel@nongnu.org; Thu, 20 Oct 2022 05:59:04 -0400 Received: from mout.kundenserver.de ([212.227.126.133]:39193) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1olSKF-000098-Mb for qemu-devel@nongnu.org; Thu, 20 Oct 2022 05:58:58 -0400 Received: from lenovo-t14s.redhat.com ([82.142.8.70]) by mrelayeu.kundenserver.de (mreue009 [212.227.15.167]) with ESMTPSA (Nemesis) id 1M5Q6n-1omHfj2K7J-001R3M; Thu, 20 Oct 2022 11:58:50 +0200 From: Laurent Vivier To: qemu-devel@nongnu.org Cc: Jason Wang , David Gibson , "Michael S. Tsirkin" , Stefano Brivio , Laurent Vivier , alex.williamson@redhat.com Subject: [PATCH v3 1/2] virtio-net: fix bottom-half packet TX on asynchronous completion Date: Thu, 20 Oct 2022 11:58:45 +0200 Message-Id: <20221020095846.63831-2-lvivier@redhat.com> X-Mailer: git-send-email 2.37.3 In-Reply-To: <20221020095846.63831-1-lvivier@redhat.com> References: <20221020095846.63831-1-lvivier@redhat.com> MIME-Version: 1.0 X-Provags-ID: V03:K1:oMFlOkoONldzjUS74jD2fpic0+3Lf6ct3UCOMqPiAI+iLhYYBoe auzXbOsRbiMRhWVOFEMb0Xin/UIcrno34KePgATO+3d2RMfReUCm1vl2kfjA3+d0I+/QL4z Ugo/KP9zMR94Msg9TF/WBtl/QLaIoeKSlHvadbUmq3MUwtyM94C6zxtj+AoDNeog6uDcN// fezhv1S7lH7P4WU1G+zVg== X-UI-Out-Filterresults: notjunk:1;V03:K0:kNZ1u7iKMU4=:D21cWwA3U3yoGm+RdDECAi VarEHgXYAVMNEseoZj4u6r09vPAusEu8ya2Xzy61cL8WBOR/1EiCj/XlvqqMKM7DlnZUxL5qw AtnRjk5hUe+bbNBGKvQdd7Kw8Zstw//NShi8IFz4NzqfaNt5aAbCniC0/fUX1njfT77wVqTBT sdCex1QbzCW9HLJbVD/msMTyr1wr2OmLprmWQmsYFMoPqDgpms9ogl43rrcoqqZX1xDlvYmLW OjpvCBb/UasA+OrvpivlPSKhCHrvNLMHg2qSaTtahI7kl9Fq2SyumM3Lz0liedfsTPHb64xlH ccuItmDTTUVMf+7rBnWNMHeEpNJatJ3JB9I/DSSkzXzwLs778z5KCLBbcAXrHCu+GM48EO6SD KZHgq5pPwfrjnvz5DQb1s5uhTaopcJPwmPZePs9tb8j5Dfy8Kgn2f4Dq7DkawWcOJ6wBchsaj m92Z7WgIqePVkS3wdI9a6AVYWFpy0JELpOnf6afGqmpPZOOq2WNqCAe4F1cUV/vo8YBxV6rrO seLgEkkGqcHXMF5cw3UbG/EBQ9610WIptUqBoXHPxdsTjefiH/Ahp/VQBEduDTEMq+Z8inE13 5lwFSzz9O8rl3CLUSl8QUoeeRcv5w+BznnflGN0gAnUHUFU5+9jyUqokf6UbwDyP0rlFCJWuu 2PoC5cdAuPEtFSkzw/K+aesd9GtHkcQ3V0klz+qMJ+15hLjyvjr/QoElOt3vAB7F9caFFoZjt uh6wHRMhbtdZExjUfMpUXkhvnW20Iiev4uYgndXFncsMK4OPLm/zKqp47QvhiOsOGOvtUaG+h RFNNjP4 Received-SPF: permerror client-ip=212.227.126.133; envelope-from=lvivier@redhat.com; helo=mout.kundenserver.de X-Spam_score_int: -18 X-Spam_score: -1.9 X-Spam_bar: - X-Spam_report: (-1.9 / 5.0 requ) BAYES_00=-1.9, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-0.001, SPF_FAIL=0.001, SPF_HELO_NONE=0.001 autolearn=no 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" When virtio-net is used with the socket netdev backend, the backend can be busy and not able to collect new packets. In this case, net_socket_receive() returns 0 and registers a poll function to detect when the socket is ready again. In virtio_net_tx_bh(), virtio_net_flush_tx() forwards the 0, the virtio notifications are disabled and the function is not re-scheduled, waiting for the backend to be ready. When the socket netdev backend is again able to send packets, the poll function re-starts to flush remaining packets. This is done by calling virtio_net_tx_complete(). It re-enables notifications and calls again virtio_net_flush_tx(). But it seems if virtio_net_flush_tx() reaches the tx_burst value all the queue is not flushed and no new notification is sent to re-schedule virtio_net_tx_bh(). Nothing re-start to flush the queue and remaining packets are stuck in the queue. To fix that, detect in virtio_net_tx_complete() if virtio_net_flush_tx() has been stopped by tx_burst and if yes re-schedule the bottom half function virtio_net_tx_bh() to flush the remaining packets. This is what is done in virtio_net_tx_bh() when the virtio_net_flush_tx() is synchronous, and completly by-passed when the operation needs to be asynchronous. Fixes: a697a334b3c4 ("virtio-net: Introduce a new bottom half packet TX") Cc: alex.williamson@redhat.com Signed-off-by: Laurent Vivier Acked-by: Michael S. Tsirkin --- hw/net/virtio-net.c | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-) diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c index e9f696b4cfeb..1fbf2f3e19a7 100644 --- a/hw/net/virtio-net.c +++ b/hw/net/virtio-net.c @@ -2526,6 +2526,7 @@ static void virtio_net_tx_complete(NetClientState *nc, ssize_t len) VirtIONet *n = qemu_get_nic_opaque(nc); VirtIONetQueue *q = virtio_net_get_subqueue(nc); VirtIODevice *vdev = VIRTIO_DEVICE(n); + int ret; virtqueue_push(q->tx_vq, q->async_tx.elem, 0); virtio_notify(vdev, q->tx_vq); @@ -2534,7 +2535,17 @@ static void virtio_net_tx_complete(NetClientState *nc, ssize_t len) q->async_tx.elem = NULL; virtio_queue_set_notification(q->tx_vq, 1); - virtio_net_flush_tx(q); + ret = virtio_net_flush_tx(q); + if (q->tx_bh && ret >= n->tx_burst) { + /* + * the flush has been stopped by tx_burst + * we will not receive notification for the + * remainining part, so re-schedule + */ + virtio_queue_set_notification(q->tx_vq, 0); + qemu_bh_schedule(q->tx_bh); + q->tx_waiting = 1; + } } /* TX */