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=unavailable 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 DC160C433E3 for ; Thu, 20 Aug 2020 00:12:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A19122075E for ; Thu, 20 Aug 2020 00:12:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1597882356; bh=iXmAtY7BG2mwDIC/wHHpkcNbC6q/kDidRTK1GVKOgL8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=UKGdsk3F5j/EL+wkWjthWmNdAWNfzM5VVzGURsmGIK6Jg3MWBifk2gj7VH6iMZ9Vu eIETcLsp8b2I4ktpTFQkqT2GVnGU28cpyD7mBumuHkRiooNhodRQ/TiRgK4d5LWYbW uCORmYglkj62DG0UUMd9iOtk1p8jn37mGr7VS0cE= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728749AbgHTAM3 (ORCPT ); Wed, 19 Aug 2020 20:12:29 -0400 Received: from mail.kernel.org ([198.145.29.99]:57956 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726985AbgHTABp (ORCPT ); Wed, 19 Aug 2020 20:01:45 -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 8AA29208E4; Thu, 20 Aug 2020 00:01:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1597881705; bh=iXmAtY7BG2mwDIC/wHHpkcNbC6q/kDidRTK1GVKOgL8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=0zWo7fq0cLrHlElAtTb9Mim3elpKxPdzj7sstxaldL62Tf98esOKMPiX/hsY25XPU tg3voCtEG+HzE35Ia07OebvxiX5lg3ufkuOF56W+pYzX65II3KNbVcwAefR8mEmvHf a7ezah4k4u3aRLYoKEGTnBihjHeBkujXaEamoVbI= 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 5.8 21/27] virtio_ring: Avoid loop when vq is broken in virtqueue_poll Date: Wed, 19 Aug 2020 20:01:10 -0400 Message-Id: <20200820000116.214821-21-sashal@kernel.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20200820000116.214821-1-sashal@kernel.org> References: <20200820000116.214821-1-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 58b96baa8d488..4f7c73e6052f6 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); -- 2.25.1