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 X-Spam-Level: X-Spam-Status: No, score=-13.0 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,UNPARSEABLE_RELAY,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 10E02C433E0 for ; Sun, 2 Aug 2020 05:57:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E41212075A for ; Sun, 2 Aug 2020 05:57:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726023AbgHBF4s (ORCPT ); Sun, 2 Aug 2020 01:56:48 -0400 Received: from out30-57.freemail.mail.aliyun.com ([115.124.30.57]:56764 "EHLO out30-57.freemail.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725798AbgHBF4r (ORCPT ); Sun, 2 Aug 2020 01:56:47 -0400 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R611e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e07425;MF=wenan.mao@linux.alibaba.com;NM=1;PH=DS;RN=6;SR=0;TI=SMTPD_---0U4S29OA_1596347795; Received: from VM20200710-3.tbsite.net(mailfrom:wenan.mao@linux.alibaba.com fp:SMTPD_---0U4S29OA_1596347795) by smtp.aliyun-inc.com(127.0.0.1); Sun, 02 Aug 2020 13:56:44 +0800 From: Mao Wenan To: mst@redhat.com, jasowang@redhat.com Cc: virtualization@lists.linux-foundation.org, linux-kernel@vger.kernel.org, kernel-janitors@vger.kernel.org, Mao Wenan Subject: [PATCH -next v2] virtio_net: Avoid loop in virtnet_poll Date: Sun, 2 Aug 2020 13:56:33 +0800 Message-Id: <1596347793-55894-1-git-send-email-wenan.mao@linux.alibaba.com> X-Mailer: git-send-email 1.8.3.1 In-Reply-To: <20200802003818-mutt-send-email-mst@kernel.org> References: <20200802003818-mutt-send-email-mst@kernel.org> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The loop may exist if vq->broken is true, virtqueue_get_buf_ctx_packed or virtqueue_get_buf_ctx_split will return NULL, so virtnet_poll will reschedule napi to receive packet, it will lead cpu usage(si) to 100%. call trace as below: virtnet_poll virtnet_receive virtqueue_get_buf_ctx virtqueue_get_buf_ctx_packed virtqueue_get_buf_ctx_split virtqueue_napi_complete virtqueue_poll //return true virtqueue_napi_schedule //it will reschedule napi To fix this, return false if vq is broken in virtqueue_poll. Signed-off-by: Mao Wenan --- v1->v2: fix it in virtqueue_poll suggested by Michael S. Tsirkin drivers/virtio/virtio_ring.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c index 58b96ba..4f7c73e 100644 --- a/drivers/virtio/virtio_ring.c +++ b/drivers/virtio/virtio_ring.c @@ -1960,6 +1960,9 @@ bool virtqueue_poll(struct virtqueue *_vq, unsigned last_used_idx) { struct vring_virtqueue *vq = to_vvq(_vq); + if (unlikely(vq->broken)) + return false; + virtio_mb(vq->weak_barriers); return vq->packed_ring ? virtqueue_poll_packed(_vq, last_used_idx) : virtqueue_poll_split(_vq, last_used_idx); -- 1.8.3.1