From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753773AbeASGyz (ORCPT ); Fri, 19 Jan 2018 01:54:55 -0500 Received: from aserp2130.oracle.com ([141.146.126.79]:45202 "EHLO aserp2130.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750722AbeASGyq (ORCPT ); Fri, 19 Jan 2018 01:54:46 -0500 Subject: Re: [PATCH V5 2/2] nvme-pci: fixup the timeout case when reset is ongoing To: Keith Busch Cc: sagi@grimberg.me, james.smart@broadcom.com, linux-nvme@lists.infradead.org, linux-kernel@vger.kernel.org, axboe@fb.com, maxg@mellanox.com, hch@lst.de References: <1516270202-8051-1-git-send-email-jianchao.w.wang@oracle.com> <1516270202-8051-3-git-send-email-jianchao.w.wang@oracle.com> <20180119045944.GC12043@localhost.localdomain> <0b74b36d-ecb5-e9e2-2900-6dc9c9699658@oracle.com> <20180119060521.GD12043@localhost.localdomain> From: "jianchao.wang" Message-ID: <23b3ea15-aed0-3b2f-e02f-124fe6fdf618@oracle.com> Date: Fri, 19 Jan 2018 14:53:37 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.5.0 MIME-Version: 1.0 In-Reply-To: <20180119060521.GD12043@localhost.localdomain> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Proofpoint-Virus-Version: vendor=nai engine=5900 definitions=8778 signatures=668654 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=2 malwarescore=0 phishscore=0 bulkscore=0 spamscore=0 mlxscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1711220000 definitions=main-1801190087 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Keith Thanks for your kindly reminding. On 01/19/2018 02:05 PM, Keith Busch wrote: >>> The driver may be giving up on the command here, but that doesn't mean >>> the controller has. We can't just end the request like this because that >>> will release the memory the controller still owns. We must wait until >>> after nvme_dev_disable clears bus master because we can't say for sure >>> the controller isn't going to write to that address right after we end >>> the request. >>> >> Yes, but the controller is going to be reseted or shutdown at the moment, >> even if the controller accesses a bad address and goes wrong, everything will >> be ok after reset or shutdown. :) > Hm, I don't follow. DMA access after free is never okay. Yes, this may cause unexpected memory corruption. Thanks Jianchao