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Wed, 10 Dec 2025 17:35:21 +0000 (GMT) Message-ID: Subject: Re: [PATCH v2 1/2] Revert "PCI/IOV: Add PCI rescan-remove locking when enabling/disabling SR-IOV" From: Gerd Bayer To: Niklas Schnelle , Bjorn Helgaas Cc: Lukas Wunner , Keith Busch , Matthew Rosato , Benjamin Block , Halil Pasic , Farhan Ali , Julian Ruess , Heiko Carstens , Vasily Gorbik , Alexander Gordeev , linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org Date: Wed, 10 Dec 2025 18:35:21 +0100 In-Reply-To: <20251119-revert_sriov_lock-v2-1-ea50eb1e8f96@linux.ibm.com> References: <20251119-revert_sriov_lock-v2-0-ea50eb1e8f96@linux.ibm.com> <20251119-revert_sriov_lock-v2-1-ea50eb1e8f96@linux.ibm.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.58.2 (3.58.2-1.fc43) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-TM-AS-GCONF: 00 X-Proofpoint-GUID: SYQ97Xw60bEokNZQoxYYXdoMg9G9vn-r X-Proofpoint-ORIG-GUID: SYQ97Xw60bEokNZQoxYYXdoMg9G9vn-r X-Authority-Analysis: v=2.4 cv=aY9sXBot c=1 sm=1 tr=0 ts=6939af5f cx=c_pps a=AfN7/Ok6k8XGzOShvHwTGQ==:117 a=AfN7/Ok6k8XGzOShvHwTGQ==:17 a=IkcTkHD0fZMA:10 a=wP3pNCr1ah4A:10 a=VkNPw1HP01LnGYTKEx00:22 a=VwQbUJbxAAAA:8 a=VnNF1IyMAAAA:8 a=MQOrj0ii5XhWA5c1uIUA:9 a=QEXdDO2ut3YA:10 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUxMjA2MDAwNyBTYWx0ZWRfX19Nv77mEtEVA yzNJzuqfmnFo2/N05qAPZgA+/62b0y0TeUeIutO5JTV7aqTxZAMgUVlks5V1BFnR2aysmvqXPZG XyBe+/4Z8333ge2eQ1SXU6MZSqy3V7RA77wHuqqLru4Ks/0J7ENvAp2s1mxwKKiE38cwqw2Me7m O1VCYR3jKeAWgmVhSTv7KAjOJwWNyQRWcPT4+8BOeVSJFbe8GJvmki0kjVJ8kC6phEgiezJmvCL oeTcWc0gT0Nc/Asrr2DSoiqtqQFBX6jczeuMDdUbWmiDRMV61XNF6EH49fgbnNoNdtabdDkTmfy QK1iUZMcEFNePtglYQG3ahjMaks/8LX4K6bHP+WWD9hHZ6Ywtr7QhM6m6vuTWRv+gHWLEMs6WBT ie/7W+y7TflIkUhy/CqiwAOrx8Oa/A== X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1121,Hydra:6.1.9,FMLib:17.12.100.49 definitions=2025-12-10_02,2025-12-09_03,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 suspectscore=0 clxscore=1015 phishscore=0 lowpriorityscore=0 bulkscore=0 adultscore=0 impostorscore=0 malwarescore=0 priorityscore=1501 spamscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2510240000 definitions=main-2512060007 On Wed, 2025-11-19 at 13:34 +0100, Niklas Schnelle wrote: > This reverts commit 05703271c3cd ("PCI/IOV: Add PCI rescan-remove > locking when enabling/disabling SR-IOV") which causes a deadlock by > recursively taking pci_rescan_remove_lock when sriov_del_vfs() is called > as part of pci_stop_and_remove_bus_device(). For example with the > following sequence of commands: >=20 > $ echo > /sys/bus/pci/devices//sriov_numvfs > $ echo 1 > /sys/bus/pci/devices//remove >=20 > A trimmed trace of the deadlock on a mlx5 device is as below: >=20 > mutex_lock_nested+0x3c/0x50 > sriov_disable+0x34/0x140 > mlx5_sriov_disable+0x50/0x80 [mlx5_core] > remove_one+0x5e/0xf0 [mlx5_core] > pci_device_remove+0x3c/0xa0 > device_release_driver_internal+0x18e/0x280 > pci_stop_bus_device+0x82/0xa0 > pci_stop_and_remove_bus_device_locked+0x5e/0x80 > remove_store+0x72/0x90 I just hit this recursive lock issue when running "reset" instead of "remove" $ echo > /sys/bus/pci/devices//sriov_numvfs $ echo 1 > /sys/bus/pci/devices//reset =20 > This is not a complete fix as it restores the issue the cited commit > tried to solve. >=20 > Cc: stable@vger.kernel.org > Fixes: 05703271c3cd ("PCI/IOV: Add PCI rescan-remove locking when enablin= g/disabling SR-IOV") > Reported-by: Benjamin Block > Reviewed-by: Benjamin Block > Signed-off-by: Niklas Schnelle > --- > drivers/pci/iov.c | 5 ----- > 1 file changed, 5 deletions(-) >=20 > diff --git a/drivers/pci/iov.c b/drivers/pci/iov.c > index 77dee43b785838d215b58db2d22088e9346e0583..ac4375954c9479b5f4a0e666b= 5215094fdaeefc2 100644 > --- a/drivers/pci/iov.c > +++ b/drivers/pci/iov.c > @@ -629,18 +629,15 @@ static int sriov_add_vfs(struct pci_dev *dev, u16 n= um_vfs) > if (dev->no_vf_scan) > return 0; > =20 > - pci_lock_rescan_remove(); > for (i =3D 0; i < num_vfs; i++) { > rc =3D pci_iov_add_virtfn(dev, i); > if (rc) > goto failed; > } > - pci_unlock_rescan_remove(); > return 0; > failed: > while (i--) > pci_iov_remove_virtfn(dev, i); > - pci_unlock_rescan_remove(); > =20 > return rc; > } > @@ -765,10 +762,8 @@ static void sriov_del_vfs(struct pci_dev *dev) > struct pci_sriov *iov =3D dev->sriov; > int i; > =20 > - pci_lock_rescan_remove(); > for (i =3D 0; i < iov->num_VFs; i++) > pci_iov_remove_virtfn(dev, i); > - pci_unlock_rescan_remove(); > } > =20 > static void sriov_disable(struct pci_dev *dev) Feel free to add my Acked-by: Gerd Bayer