linux-kernel - [PATCH v2 0/9] Error recovery for vfio-pci devices on s390x

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Message-ID: <20250825171226.1602-1-alifm@linux.ibm.com>
Date: Mon, 25 Aug 2025 10:12:17 -0700
From: Farhan Ali <alifm@...ux.ibm.com>
To: linux-s390@...r.kernel.org, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc: alex.williamson@...hat.com, helgaas@...nel.org, alifm@...ux.ibm.com,
        schnelle@...ux.ibm.com, mjrosato@...ux.ibm.com
Subject: [PATCH v2 0/9] Error recovery for vfio-pci devices on s390x

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.

I would appreciate some feedback on this series.

Thanks
Farhan

ChangeLog
---------
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 (9):
  PCI: Avoid restoring error values in config space
  PCI: Add additional checks for flr and pm reset
  PCI: Allow per function PCI slots for hypervisor isolated functions
  s390/pci: Restore airq unconditionally for the zPCI device
  s390/pci: Update the logic for detecting passthrough device
  s390/pci: Store PCI error information for passthrough devices
  vfio-pci/zdev: Add a device feature for error information
  vfio: Add a reset_done callback for vfio-pci driver
  vfio: 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         | 107 +++++++++++++++++-------------
 arch/s390/pci/pci_irq.c           |   9 +--
 drivers/pci/pci.c                 |  10 +++
 drivers/pci/slot.c                |  19 +++++-
 drivers/vfio/pci/vfio_pci_core.c  |  20 ++++--
 drivers/vfio/pci/vfio_pci_intrs.c |   3 +-
 drivers/vfio/pci/vfio_pci_priv.h  |   8 +++
 drivers/vfio/pci/vfio_pci_zdev.c  |  45 ++++++++++++-
 include/uapi/linux/vfio.h         |  14 ++++
 11 files changed, 200 insertions(+), 66 deletions(-)

-- 
2.43.0