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Mon, 9 Nov 2026 12:38:44 +0000 (GMT) Received: from [9.68.16.159] (unknown [9.68.16.159]) by smtpav03.fra02v.mail.ibm.com (Postfix) with ESMTP; Mon, 9 Nov 2026 12:38:44 +0000 (GMT) Message-ID: <4cb58287-4273-4518-8cac-aa3056dc28e2@linux.ibm.com> Date: Mon, 9 Nov 2026 13:38:44 +0100 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] vfio/ccw: Flush notoper_work before returning from reset To: Yuho Choi , Eric Farman , Matthew Rosato Cc: Halil Pasic , Heiko Carstens , Vasily Gorbik , Alexander Gordeev , Sven Schnelle , Vineeth Vijayan , Peter Oberparleiter , Alex Williamson , Jason Gunthorpe , linux-s390@vger.kernel.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org References: <20261106191029.469837-2-oss.patchbox@gmail.com> Content-Language: en-US From: Christian Borntraeger In-Reply-To: <20261106191029.469837-2-oss.patchbox@gmail.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-Reinject: loops=2 maxloops=12 X-Authority-Analysis: v=2.4 cv=J+M/fwnS c=1 sm=1 tr=0 ts=6af1bed9 cx=c_pps a=GFwsV6G8L6GxiO2Y/PsHdQ==:117 a=GFwsV6G8L6GxiO2Y/PsHdQ==:17 a=IkcTkHD0fZMA:10 a=zJRp6_cAMcgA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=V8glGbnc2Ofi9Qvn3v5h:22 a=pGLkceISAAAA:8 a=MGMQWwHRxuE3iItJiNIA:9 a=QEXdDO2ut3YA:10 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYxMTA5MDA0OCBTYWx0ZWRfX5BjHtSlLwIWk VEjOYNO5uMgmvrdxkyVrvQJ7aDCRSOhbiN5CA5oKC0bpU2O+siO2aHy8hjsopmTEbCnLMPD5Otr kgoqfPcm+e1QUg0yIpFTHInOIAjsDQOD6x9FfJcqkSl0bZI2IJAk2f3mEBissh2wt9uLcfZJHna JvFja5C0UB8km5PZRREj0txU9M8rydZTrUi5zpvYVBD8dSTiZxeMNfzwX+jYmzXcoJKGCVYdKyt tUrjcmzfSxO9pb25o8u28vMorw0olY/sqeUf2Y/U4tX8o2T3PCosxnIW2ZE/OTrAvoUIGX6o8Ur 370uNunIftqRYkMxyq7PUliptwIFu3aJhbGUGQ/HA4lpPlAi9Z4tw/stDO0ekmZrZ87zXSWHZT+ yh37/rdRtZKyiCh0UWjDAKQRU9WPE/XAlUaWWDfFwaO0Vnx399LNiXkpHWMocQvvGuWKwgik3hf VNUmYG4hpFaOkk1UAJQ== X-Proofpoint-Spam-Info: AW1haW4tMjYxMTA5MDA0OCBTYWx0ZWRfX9wRkrOhZw+yU yD5VzBkW+s70LodyExEuv6RNKfHbNcBjgCjzOmsrLl9DYmeR609ZR/S9fuCclc95sMNrQJLwgVx Eq4AWIrD2iMOW8yoC/6UDZfnNmvYey8= X-Proofpoint-GUID: 7PHhsw1CXkWbchPBwpBLaSAEodvwuPfj X-Proofpoint-ORIG-GUID: HbA3pKVglMtZK2G6Mk2_WubN5R9GxW8m X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1176,Hydra:6.1.138,FMLib:17.12.100.49 definitions=2026-11-09_04,2026-11-06_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 lowpriorityscore=0 phishscore=0 bulkscore=0 adultscore=0 suspectscore=0 malwarescore=0 clxscore=1015 priorityscore=1501 impostorscore=0 spamscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2611040001 definitions=main-2611090048 Am 06.11.26 um 20:10 schrieb Yuho Choi: > vfio_ccw_dma_unmap() is the DMA invalidation callback, which must unpin > the pages covering the range before it returns. It calls > vfio_ccw_mdev_reset(), which raises a CLOSE event. > > On the normal path fsm_close() calls cp_free() itself, so the pages are > unpinned synchronously. But if the subchannel cannot be disabled or > quiesced, fsm_close() falls through to a NOT_OPER event. Since commit > 0c11f61a876e ("s390/vfio_ccw: Move cp cleanup out of not operational"), > fsm_notoper() only queues notoper_work, which is where cp_free() then > runs. That commit flushes the work in vfio_ccw_mdev_close_device() and > vfio_ccw_mdev_release_dev(), but nothing waits for it on the reset > path, so the callback returns with the pages still pinned. > > Because notoper_work runs asynchronously, vfio_dma_do_unmap() can exhaust > its 10 retries before cp_free() completes, hitting BUG_ON(++retries > 10) > and taking the host down. A further CLOSE cannot help either, as both > CLOSE and OPEN are fsm_nop in the NOT_OPER state. Does the the iommufd backend have the same problem? iopt_unmap_iova_range() keeps calling the unmap callback and gives up with WARN_ON(tries > 100) and -EDEADLOCK. So that path is also fixed, I guess. [..] > Fixes: 0c11f61a876e ("s390/vfio_ccw: Move cp cleanup out of not operational") cc stable ? > Signed-off-by: Yuho Choi Eric, Matt, can you have a look? [..]