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Mon, 6 Apr 2026 17:23:47 +0000 (GMT) Message-ID: <8c2a8b6b-f4a9-4a4e-baf4-7de73b11b468@linux.ibm.com> Date: Mon, 6 Apr 2026 10:23:47 -0700 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 v12 0/7] Error recovery for vfio-pci devices on s390x To: linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org, Bjorn Helgaas , Alex Williamson Cc: lukas@wunner.de, clg@redhat.com, kbusch@kernel.org, schnelle@linux.ibm.com, mjrosato@linux.ibm.com References: <20260330174011.1161-1-alifm@linux.ibm.com> Content-Language: en-US From: Farhan Ali In-Reply-To: <20260330174011.1161-1-alifm@linux.ibm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-GUID: KsBcYtJCJhMYG3F-l2laWhv4dbW5enro X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNDA2MDE3MCBTYWx0ZWRfX1LAdjt7kLyu1 rGK5ak5UWX5ZvWowLmvUn81hcBqxzcI71sRkJIkBV8iRmt7NyWXckmaHgJ85ZLDpO83YcYIzGHk VNyn1aaTKqz21FyeF0iGIcJZ8YpDvrh1psSpcqc3GFL9PyznN1ajTipmUGmYs5iEdpqhc8aPISb aBZkDOJpi9CVZE9TopFYnCwDONJBklgqFZB7BwIWuNNWVLjuF/u62U0nrVpV2y9mwlGAUYJNicF 90FLqOh9xBtDfw04nqAMXnll2EfNWmxs0oD2otKyLocrk8BZCOo54/oDAVwVUmJ9Jf5qF7kWP+K vmJySfEJahnODfAoihsLFdMDLPaGSELd18PNpE3XWX0jSDkn4Zd0baDKM8N3qzqI3u3PzPXhxjO vo4wop17aqRuJgl7n/vymyHoLTrLdt7F9+wdi08qpZawwztUeyjL8GuQDThJBoUr+jjEOZY7zmz Xo/526XAeQuhWzAnqwg== X-Authority-Analysis: v=2.4 cv=b+u/I9Gx c=1 sm=1 tr=0 ts=69d3ec26 cx=c_pps a=AfN7/Ok6k8XGzOShvHwTGQ==:117 a=AfN7/Ok6k8XGzOShvHwTGQ==:17 a=IkcTkHD0fZMA:10 a=A5OVakUREuEA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=Y2IxJ9c9Rs8Kov3niI8_:22 a=VwQbUJbxAAAA:8 a=VnNF1IyMAAAA:8 a=LeXJYMSVX8EPm9N_UQ0A:9 a=QEXdDO2ut3YA:10 X-Proofpoint-ORIG-GUID: KsBcYtJCJhMYG3F-l2laWhv4dbW5enro 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=2026-04-06_03,2026-04-03_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 suspectscore=0 phishscore=0 bulkscore=0 adultscore=0 lowpriorityscore=0 impostorscore=0 malwarescore=0 spamscore=0 priorityscore=1501 clxscore=1015 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2603050001 definitions=main-2604060170 Gentle ping on this series. Hope I have been able address the concerns from last revision. Thanks Farhan On 3/30/2026 10:40 AM, Farhan Ali wrote: > 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 > --------- > 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'") > > > v10 series https://lore.kernel.org/all/20260302203325.3826-1-alifm@linux.ibm.com/ > v10 -> v11 > - Rebase on pci/next to handle merge conflicts with patch 1. > > - Typo fixup in commit message (patch 4) and use guard() for mutex > (patch 6). > > v9 series https://lore.kernel.org/all/20260217182257.1582-1-alifm@linux.ibm.com/ > v9 -> v10 > - Change pci_slot number to u16 (patch 1). > > - Avoid saving invalid config space state if config space is > inaccessible in the device reset path. It uses the same patch as in v8 > with R-b from Niklas. > > - Rebase on 7.0.0-rc2 > > > v8 series https://lore.kernel.org/all/20260122194437.1903-1-alifm@linux.ibm.com/ > v8 -> v9 > - Avoid saving PCI config space state in reset path (patch 3) (suggested by Bjorn) > > - Add explicit version to struct vfio_device_feature_zpci_err (patch 7). > > - Rebase on 6.19 > > > v7 series https://lore.kernel.org/all/20260107183217.1365-1-alifm@linux.ibm.com/ > v7 -> v8 > - Rebase on 6.19-rc4 > > - Address feedback from Niklas and Julien. > > > v6 series https://lore.kernel.org/all/2c609e61-1861-4bf3-b019-a11c137d26a5@linux.ibm.com/ > v6 -> v7 > - Rebase on 6.19-rc4 > > - Update commit message based on Niklas's suggestion (patch 3). > > v5 series https://lore.kernel.org/all/20251113183502.2388-1-alifm@linux.ibm.com/ > v5 -> v6 > - Rebase on 6.18 + Lukas's PCI: Universal error recoverability of > devices series (https://lore.kernel.org/all/cover.1763483367.git.lukas@wunner.de/) > > - Re-work config space accessibility check to pci_dev_save_and_disable() (patch 3). > This avoids saving the config space, in the reset path, if the device's config space is > corrupted or inaccessible. > > v4 series https://lore.kernel.org/all/20250924171628.826-1-alifm@linux.ibm.com/ > v4 -> v5 > - Rebase on 6.18-rc5 > > - Move bug fixes to the beginning of the series (patch 1 and 2). These patches > were posted as a separate fixes series > https://lore.kernel.org/all/a14936ac-47d6-461b-816f-0fd66f869b0f@linux.ibm.com/ > > - Add matching pci_put_dev() for pci_get_slot() (patch 6). > > v3 series https://lore.kernel.org/all/20250911183307.1910-1-alifm@linux.ibm.com/ > v3 -> v4 > - Remove warn messages for each PCI capability not restored (patch 1) > > - Check PCI_COMMAND and PCI_STATUS register for error value instead of device id > (patch 1) > > - Fix kernel crash in patch 3 > > - Added reviewed by tags > > - Address comments from Niklas's (patches 4, 5, 7) > > - Fix compilation error non s390x system (patch 8) > > - Explicitly align struct vfio_device_feature_zpci_err (patch 8) > > > v2 series https://lore.kernel.org/all/20250825171226.1602-1-alifm@linux.ibm.com/ > v2 -> v3 > - Patch 1 avoids saving any config space state if the device is in error > (suggested by Alex) > > - Patch 2 adds additional check only for FLR reset to try other function > reset method (suggested by Alex). > > - Patch 3 fixes a bug in s390 for resetting PCI devices with multiple > functions. Creates a new flag pci_slot to allow per function slot. > > - Patch 4 fixes a bug in s390 for resource to bus address translation. > > - Rebase on 6.17-rc5 > > > v1 series https://lore.kernel.org/all/20250813170821.1115-1-alifm@linux.ibm.com/ > v1 - > v2 > - Patches 1 and 2 adds some additional checks for FLR/PM reset to > try other function reset method (suggested by Alex). > > - Patch 3 fixes a bug in s390 for resetting PCI devices with multiple > functions. > > - Patch 7 adds a new device feature for zPCI devices for the VFIO_DEVICE_FEATURE > ioctl. The ioctl is used by userspace to retriece any PCI error > information for the device (suggested by Alex). > > - Patch 8 adds a reset_done() callback for the vfio-pci driver, to > restore the state of the device after a reset. > > - Patch 9 removes the pcie check for triggering VFIO_PCI_ERR_IRQ_INDEX. > > > 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 | 30 ++++++++ > arch/s390/pci/pci.c | 1 + > arch/s390/pci/pci_event.c | 113 +++++++++++++++++------------- > 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 | 45 +++++++++++- > include/linux/pci.h | 8 ++- > include/uapi/linux/vfio.h | 18 +++++ > 12 files changed, 247 insertions(+), 69 deletions(-) >