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=-13.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,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 AFC1AC433DF for ; Thu, 20 Aug 2020 00:05:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 88E61208C7 for ; Thu, 20 Aug 2020 00:05:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1597881947; bh=MGpCxETfVBdJUi9yLlAn0NS7XSW2oCvWtdSw+Yn9XmU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=Mivu9DtnF5AoOxhrlczR+h3Lpr14jbHCOq1VZ4AwjTrENUQ02vqv97JFBemBXTrXu Ejz8TaBTsSgRY998ImHhiEsB/ER05Hcq6QodywIDdTyhuspR3Du1E17ioTtowoMsGx bxu+u6S6e+aMBrzpzBvsfPkD6DioYNe6M/ibfJw0= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728549AbgHTAFf (ORCPT ); Wed, 19 Aug 2020 20:05:35 -0400 Received: from mail.kernel.org ([198.145.29.99]:34164 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728400AbgHTAEC (ORCPT ); Wed, 19 Aug 2020 20:04:02 -0400 Received: from sasha-vm.mshome.net (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 7DEF9208E4; Thu, 20 Aug 2020 00:04:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1597881842; bh=MGpCxETfVBdJUi9yLlAn0NS7XSW2oCvWtdSw+Yn9XmU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=uzYYOSYy/en7jhJ4KcCNCWsaP3UdpPLRISTmWiRcsQnN/PZkySSq0vhCe/M02vWBm ElNDzwsjb8/1fC/a6gPK8aQN+1IcefbSnCEdz5qrVbmLNe6YlWfGcAwk4lNTQjvz0Z I8n3dV2OIkLi4c4eDpUxyahOZVoet1s8BvgMksBo= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Mao Wenan , "Michael S . Tsirkin" , Jason Wang , Sasha Levin , virtualization@lists.linux-foundation.org Subject: [PATCH AUTOSEL 4.9 09/11] virtio_ring: Avoid loop when vq is broken in virtqueue_poll Date: Wed, 19 Aug 2020 20:03:46 -0400 Message-Id: <20200820000348.215911-9-sashal@kernel.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20200820000348.215911-1-sashal@kernel.org> References: <20200820000348.215911-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Mao Wenan [ Upstream commit 481a0d7422db26fb63e2d64f0652667a5c6d0f3e ] 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 Acked-by: Michael S. Tsirkin Link: https://lore.kernel.org/r/1596354249-96204-1-git-send-email-wenan.mao@linux.alibaba.com Signed-off-by: Michael S. Tsirkin Acked-by: Jason Wang Signed-off-by: Sasha Levin --- 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 e459cd7302e27..5cad9f41c238b 100644 --- a/drivers/virtio/virtio_ring.c +++ b/drivers/virtio/virtio_ring.c @@ -785,6 +785,9 @@ 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 (u16)last_used_idx != virtio16_to_cpu(_vq->vdev, vq->vring.used->idx); } -- 2.25.1