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Tue, 11 Aug 2026 18:20:52 +0000 (GMT) Received: from [9.61.146.44] (unknown [9.61.146.44]) by smtpav03.dal12v.mail.ibm.com (Postfix) with ESMTP; Tue, 11 Aug 2026 18:20:52 +0000 (GMT) Message-ID: Date: Tue, 11 Aug 2026 14:20:52 -0400 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 7/8] s390/vfio-ap: Fix required lock not held during display of sysfs status attribute From: Matthew Rosato To: Anthony Krowiak , linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org Cc: jjherne@linux.ibm.com, borntraeger@de.ibm.com, pasic@linux.ibm.com, alex@shazbot.org, kwankhede@nvidia.com, fiuczy@linux.ibm.com, pbonzini@redhat.com, frankja@linux.ibm.com, imbrenda@linux.ibm.com, agordeev@linux.ibm.com, hca@linux.ibm.com, gor@linux.ibm.com, stable@vger.kernel.org References: <20260810192257.1208410-1-akrowiak@linux.ibm.com> <20260810192257.1208410-8-akrowiak@linux.ibm.com> <5d755e25-be9d-4227-b06c-63563fcce0b5@linux.ibm.com> Content-Language: en-US In-Reply-To: <5d755e25-be9d-4227-b06c-63563fcce0b5@linux.ibm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Authority-Analysis: v=2.4 cv=AMtp2X5w c=1 sm=1 tr=0 ts=6a7b6808 cx=c_pps a=AfN7/Ok6k8XGzOShvHwTGQ==:117 a=AfN7/Ok6k8XGzOShvHwTGQ==:17 a=IkcTkHD0fZMA:10 a=Sv0fKeRqtYgA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=Y2IxJ9c9Rs8Kov3niI8_:22 a=VwQbUJbxAAAA:8 a=VnNF1IyMAAAA:8 a=8gt7DvUvnbPXcpqzDXYA:9 a=QEXdDO2ut3YA:10 X-Proofpoint-GUID: QXkwCKTxdmHT9EodZW_CLTOpkyMSeqES X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwODExMDE1MSBTYWx0ZWRfXzkphd+Oi70b8 iHk+3rbzpGMcmzIUqXHzHRnX3m0Lx6wKlOyHY80b6Ymy3eRl6qgazeE/WtZWFahGeqq7PKDz/34 r+RuC68cfQWgC/RSYt3WSbeS1qFl3eW3aP1/iHrDs0DYb9Xq4UUZ/n4Qcj8q++zrOQe5g7D4Uwe 2SP6L3ihhPaQ+tkEzZqmq+yA5V9EoZTAyWz4zUpJ3DDm5QmI1cxrzAL2PI2GDrCQiylAe/dAhJe bGqqJxfRbyWLBxYxc4tsL3HshBqAwopOFxy9FVca2xVStTt0F4RkCKifnuXckZIotxd+WPfNqLK ibRdfIL5W8FVg8BFeRE/ecSbtwWGJhnAnBm5FYa41RorAb20h/IGaAMZwFFPYsRJ3fzgrk/g2rh 203LxYB9IyClu3YyWbn7eEr0Da9diQdOON3M5p6LXMwF1agWwr+uK6LwISC3Kvd1e+OR5AVfIsz +cZrulK8Yl3hfOvxNEw== X-Proofpoint-ORIG-GUID: QXkwCKTxdmHT9EodZW_CLTOpkyMSeqES X-Proofpoint-Spam-Info: AW1haW4tMjYwODExMDE1MSBTYWx0ZWRfX/1xuGVnaCNcZ eiqV9Hx2Y0twcYr0VeaY0QB+C3QqNYBklia7pchhjM4SCBIhxvwuyjDdg+wc7uuOdKzdlfcM7A6 0Z8M3pvacAoWM9NmEgczgLsnwmWnZXw= X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1176,Hydra:6.1.134,FMLib:17.12.100.49 definitions=2026-08-11_04,2026-08-10_03,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 suspectscore=0 adultscore=0 lowpriorityscore=0 clxscore=1015 priorityscore=1501 impostorscore=0 phishscore=0 spamscore=0 bulkscore=0 malwarescore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2608110151 On 8/11/26 2:03 PM, Matthew Rosato wrote: > On 8/10/26 3:22 PM, Anthony Krowiak wrote: >> The status_show function that supports display of the status attribute of >> the devices in /sys/bus/ap/devices calls the vfio_ap_mdev_for_queue >> function which iterates the matrix_dev->mdev_list to find the object >> representing the queue device whose status is to be displayed. In order to >> traverse this list, the matrix_dev->guests_lock mutex must be held which is >> not the case. >> >> To fix this, the guests_lock mutex is taken prior to taking the >> matrix_dev->mdevs_lock mutex in the status_show function. It is taken >> there rather than the vfio_ap_mdev_for_queue function - where it is >> needed - because it must be taken prior to the mdevs_lock mutex in order to >> adhere to the proper locking order and prevent a lockdep splat; also >> because the mdevs_lock is needed there to access fields within >> the matrix_mdev object in that function. >> >> Fixes: f139862b92cf ("s390/vfio-ap: add status attribute to AP queue device's sysfs dir") >> Cc: stable@vger.kernel.org >> Signed-off-by: Anthony Krowiak > Please see my comment on patch 3. Also same idea here, I don't believe the pre-existing finding from Sashiko against this patch is resolved by this series, so have a look and consider a follow-on patch if it's a valid report.