From patchwork Fri Oct 14 13:20:03 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Laurent Vivier X-Patchwork-Id: 13007006 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 CFE98C43219 for ; Fri, 14 Oct 2022 13:22:45 +0000 (UTC) Received: from localhost ([::1]:51624 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1ojKeC-0006hZ-P9 for qemu-devel@archiver.kernel.org; Fri, 14 Oct 2022 09:22:44 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:52750) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1ojKbr-0004Ng-9f for qemu-devel@nongnu.org; Fri, 14 Oct 2022 09:20:21 -0400 Received: from mout.kundenserver.de ([217.72.192.75]:40753) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1ojKbo-0005Rh-LI for qemu-devel@nongnu.org; Fri, 14 Oct 2022 09:20:18 -0400 Received: from lenovo-t14s.redhat.com ([82.142.8.70]) by mrelayeu.kundenserver.de (mreue106 [212.227.15.183]) with ESMTPSA (Nemesis) id 1N6bwO-1pDduZ0Cqs-01868F; Fri, 14 Oct 2022 15:20:09 +0200 From: Laurent Vivier To: qemu-devel@nongnu.org Cc: Stefano Brivio , "Michael S. Tsirkin" , David Gibson , Jason Wang , Laurent Vivier , alex.williamson@redhat.com Subject: [PATCH v2 1/2] virtio-net: fix bottom-half packet TX on asynchronous completion Date: Fri, 14 Oct 2022 15:20:03 +0200 Message-Id: <20221014132004.114602-2-lvivier@redhat.com> X-Mailer: git-send-email 2.37.3 In-Reply-To: <20221014132004.114602-1-lvivier@redhat.com> References: <20221014132004.114602-1-lvivier@redhat.com> MIME-Version: 1.0 X-Provags-ID: V03:K1:LbT5j+d0cwRRc2EwgnTEbeb/8JFseST9qWis5zeywmRpvzMPDDy hzi6WpFX/LB0VXJuWfRyPgFLZu1djVdU52HHgynbti3sKT71ltY5lauEjS00yGI2IMTbcne NWW/NQiucx2WmKYlNIA0yDJUOiKkSJd1kRhjOZlcMaAGPXkUCAIqckdiHqBZ1O80XzXbb/b AYKJ3HiuYZ1aYP+pPkVpw== X-UI-Out-Filterresults: notjunk:1;V03:K0:8xJgM/Pg0NQ=:1mvMx7cmh9LPtdtVX6rRVd lgY5hvmgvgtfAFpQzrgOjvsgNnloVM93g+/6yRDpZnwNVgmnbYnutM852vhy2rCpddACslV/w lenvoWGQNK8Qb+B2eSon+eZ+iXN7PoXFdWVSu9YnZv9hTbo4sIXUkHacPDvhmEG5e2KYI+8Rs c1HVxwuVH8XaiSUZ5223E+GT7gIiuan3rQpDjpmAuXJYh779n4HXIuHN88hMH6ZLhtetqCbUv 2lmkZH6ZeAPRy6B7bwifdd48tRGPZjwoK4olEEMPkKWzAweBGIoAfVjxZtXLeTHwcX4WWtFRK bp97jd5l468BMI9JgI7lZWxvf20vc5+6snira0HrTEEsNF5PYw6VNePmAfN9ka3d85hitdsju ElkEWtgyWj6wQPrAGP1mAGWwOaLYm5savZekD+XZau95Von5aaYKHQD3KVR9D5PYJ7+hVwm/y Uusxf0nyMS3ZmM4pcIb/VnKjNs3qauHFwqAErQCTWWcgcESNaWCRPskOYLTi2+UhON2xDz2Oj 7Hvr6o0kHT5D1p+aDX9Tza3PrafA306G3hNJejAp4Gx81OputBYXTHwzGaIRZaICDvSh8O9Kv +fKf+QUQAm1gN6191oA4Xeg4pn5XKhKOG1C4q4IUZybYiAIN0EZM0AW1TKcn7V3w8UE3OdLvh DO4k2CfMqzKidFxlOOqOL1UudyeRoLH05ktLRtmFKPpkwDcLQ6BeA4CD0/6IeXWRttOPznTTr C1Jeg7EZ2lpJ7qfRhhgqwWgk2jjAMaZNerUdnDQn2R4zkhwVp5pvwaEKc3B0AIHW/wImCE3MN s+PE7T0 Received-SPF: permerror client-ip=217.72.192.75; 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, 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 */