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Thu, 14 May 2026 18:01:02 +0000 (GMT) Received: from IBM-D32RQW3.ibm.com (unknown [9.61.254.43]) by smtpav04.wdc07v.mail.ibm.com (Postfix) with ESMTP; Thu, 14 May 2026 18:01:01 +0000 (GMT) From: Farhan Ali To: linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org Cc: helgaas@kernel.org, alex@shazbot.org, alifm@linux.ibm.com, schnelle@linux.ibm.com, mjrosato@linux.ibm.com Subject: [PATCH v16 0/7] Error recovery for vfio-pci devices on s390x Date: Thu, 14 May 2026 11:00:52 -0700 Message-ID: <20260514180059.1553-1-alifm@linux.ibm.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: linux-s390@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Authority-Analysis: v=2.4 cv=Y/XIdBeN c=1 sm=1 tr=0 ts=6a060de1 cx=c_pps a=bLidbwmWQ0KltjZqbj+ezA==:117 a=bLidbwmWQ0KltjZqbj+ezA==:17 a=NGcC8JguVDcA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=U7nrCbtTmkRpXpFmAIza:22 a=VwQbUJbxAAAA:8 a=VnNF1IyMAAAA:8 a=4zu8aI-QVnT60ftJUTQA:9 a=O8hF6Hzn-FEA:10 X-Proofpoint-GUID: MyZoSdsHOM3aHuYUnl0yeILCUyuYDzPI X-Proofpoint-ORIG-GUID: MyZoSdsHOM3aHuYUnl0yeILCUyuYDzPI X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNTE0MDE3NiBTYWx0ZWRfX7iC1DPAAUOzm z7iyuqvzKhFRpib8a61XuuQ44DdHj2FCURTSGdejKHjz9PNFDtthFdEEnIU5VOhVkl6IL0ynm/V qHeB0QuDTdUvUMkguK454Ke87xK6RgsfUAyeN9+Nf86FZnzCEmjiNo1WV0irovWoDQyL0V196Jz Mlcj8B4Vwb9iFFTDi46WhJjlU7Z4k4EFzU5bLLD8oAwOu2zALsv5DdTyH+M+mVI6QW9FNINBVlk JPa+Uzb6EkAVAqkwiY1Qf44W7j2bAGYQwLOgrLh7qM7m6Ju4UfLFTDnAinESNPJDfgFXvWtCa1u 487wb7GYL3wy/iQ8wETI6K9n/q/ReAo0bqFMv5znl6kPYdHFXNtKrY+bajH5EdVxI2tjHANDlH3 AUi70xANd57mLjOC0KYOyAM08pTB3e9xUx+FlankQ28VYvBwxbdiXcsX1f3UMIsjSt8JJcmzZgm gCkOA2KmYa/AzsTIm/A== X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.51,FMLib:17.12.100.49 definitions=2026-05-14_04,2026-05-13_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 clxscore=1015 priorityscore=1501 lowpriorityscore=0 phishscore=0 malwarescore=0 suspectscore=0 bulkscore=0 spamscore=0 adultscore=0 impostorscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2605050000 definitions=main-2605140176 Hi, This Linux kernel patch series introduces support for error recovery for passthrough PCI devices on System Z (s390x). Background ---------- For PCI devices on s390x an operating system receives platform specific error events from firmware rather than through AER.Today for passthrough/userspace devices, we don't attempt any error recovery and ignore any error events for the devices. The passthrough/userspace devices are managed by the vfio-pci driver. The driver does register error handling callbacks (error_detected), and on an error trigger an eventfd to userspace. But we need a mechanism to notify userspace (QEMU/guest/userspace drivers) about the error event. Proposal -------- We can expose this error information (currently only the PCI Error Code) via a device feature. Userspace can then obtain the error information via VFIO_DEVICE_FEATURE ioctl and take appropriate actions such as driving a device reset. This is how a typical flow for passthrough devices to a VM would work: For passthrough devices to a VM, the driver bound to the device on the host is vfio-pci. vfio-pci driver does support the error_detected() callback (vfio_pci_core_aer_err_detected()), and on an PCI error s390x recovery code on the host will call the vfio-pci error_detected() callback. The vfio-pci error_detected() callback will notify userspace/QEMU via an eventfd, and return PCI_ERS_RESULT_CAN_RECOVER. At this point the s390x error recovery on the host will skip any further action(see patch 4) and let userspace drive the error recovery. Once userspace/QEMU is notified, it then injects this error into the VM so device drivers in the VM can take recovery actions. For example for a passthrough NVMe device, the VM's OS NVMe driver will access the device. At this point the VM's NVMe driver's error_detected() will drive the recovery by returning PCI_ERS_RESULT_NEED_RESET, and the s390x error recovery in the VM's OS will try to do a reset. Resets are privileged operations and so the VM will need intervention from QEMU to perform the reset. QEMU will invoke the VFIO_DEVICE_RESET ioctl to now notify the host that the VM is requesting a reset of the device. The vfio-pci driver on the host will then perform the reset on the device to recover it. Thanks Farhan ChangeLog --------- This only includes change log from last 5 revision. Older change log is available in previous version cover letter. v15 https://lore.kernel.org/all/20260505200510.2954-1-alifm@linux.ibm.com/ v15 -> v16 - Implement error recovery to be handled in user space mode or host mode based on checking mediated_recovery only once (suggested by Niklas). - Rebase on 7.1-rc3 v14 https://lore.kernel.org/all/20260421163031.704-1-alifm@linux.ibm.com/ v14 -> v15 - Fix issues identified by Sashiko (patch 4). - Address Niklas feedback (patch 4 and patch 5). - Rebase on 7.1-rc2. v13 series https://lore.kernel.org/all/20260413210608.2912-1-alifm@linux.ibm.com/ v13 -> v14 - Remove version from vfio uAPI struct. Instead reserve additional space and add a flags field. The flags will be used to indicate any usage of the reserved space (patch 5). - Remove pending_errors from vfio uAPI struct and instead return an error to indicate no more pending error for userspace to handle (patch 5). - Rebase on recent linux master v12 series https://lore.kernel.org/all/20260330174011.1161-1-alifm@linux.ibm.com/ v12 -> v13 - Add the mediated_recovery flag as part of struct zpci_ccdf_pending and protect the struct with pending_errs_lock (patch 4). - Move dequeing pending error logic to a helper function (patch 5). - Update device feature number for VFIO_DEVICE_FEATURE_ZPCI_ERROR (patch 5). - Rebase on linux-next with tag next-20260410 v11 series https://lore.kernel.org/all/20260316191544.2279-1-alifm@linux.ibm.com/ - Address Bjorn's comments from v11 (patches 1-3). - Create a common function to check config space accessibility (patch 2). - Address Alex's comments from v11 (patches 4, 5, 7). - Protect the mediated_recovery flag with the pending_errs_lock. Doing that it made sense to squash patches 5 and 6 from v11 (current patch 4). Even though the code didn't change significantly I have dropped R-b tags for it. Would appreciate another look at the patch (current patch 4). - Dropped arch specific pcibios_resource_to_bus and pcibios_bus_to_resource as its not needed for this series. Will address the issue as a standalone patch separate from this series. - Rebased on pci/next, with head at f8a1c947ccc6 ("Merge branch 'pci/misc'") Farhan Ali (7): PCI: Allow per function PCI slots to fix slot reset on s390 PCI: Avoid saving config space state if inaccessible PCI: Fail FLR when config space is inaccessible s390/pci: Store PCI error information for passthrough devices vfio-pci/zdev: Add a device feature for error information vfio/pci: Add a reset_done callback for vfio-pci driver vfio/pci: Remove the pcie check for VFIO_PCI_ERR_IRQ_INDEX arch/s390/include/asm/pci.h | 32 +++++++ arch/s390/pci/pci.c | 1 + arch/s390/pci/pci_event.c | 133 ++++++++++++++++++------------ drivers/pci/hotplug/rpaphp_slot.c | 2 +- drivers/pci/pci.c | 32 ++++++- drivers/pci/slot.c | 33 ++++++-- drivers/vfio/pci/vfio_pci_core.c | 22 +++-- drivers/vfio/pci/vfio_pci_intrs.c | 3 +- drivers/vfio/pci/vfio_pci_priv.h | 9 ++ drivers/vfio/pci/vfio_pci_zdev.c | 57 ++++++++++++- include/linux/pci.h | 8 +- include/uapi/linux/vfio.h | 30 +++++++ 12 files changed, 287 insertions(+), 75 deletions(-) -- 2.43.0