vfio/pci: Base Live Update support for VFIO device files

This series can be found on GitHub:

  https://github.com/dmatlack/linux/tree/liveupdate/vfio/cd...

This series adds the base support to preserve a VFIO device file across
a Live Update. "Base support" means that this allows userspace to
safely preserve a VFIO device file with LIVEUPDATE_SESSION_PRESERVE_FD
and retrieve it with  LIVEUPDATE_SESSION_RETRIEVE_FD, but the device
itself is not preserved in a fully running state across Live Update.

This series aims to provide a foundation on which to build the rest of
the device preservation infrastructure, including:

 - Preservation of iommufd files [1]
 - Preservation of IOMMU driver state
 - Preservation of PCI state (BAR resources, device state, bridge state, ...)
 - Preservation of vfio-pci driver state

Testing
-------

The patches at the end of this series provide comprehensive selftests
for the new code added by this series. The selftests have been validated
in both a VM environment using a virtio-net PCIe device, and in a
baremetal environment on an Intel EMR server with an Intel DSA PCIe
device.

Here is an example of how to run the new selftests:

vfio_pci_liveupdate_uapi_test:

  $ tools/testing/selftests/vfio/scripts/setup.sh 0000:00:04.0
  $ tools/testing/selftests/vfio/vfio_pci_liveupdate_uapi_test 0000:00:04.0
  $ tools/testing/selftests/vfio/scripts/cleanup.sh

vfio_pci_liveupdate_kexec_test:

  $ tools/testing/selftests/vfio/scripts/setup.sh 0000:00:04.0
  $ tools/testing/selftests/vfio/vfio_pci_liveupdate_kexec_test --stage 1 0000:00:04.0
  $ kexec ...

  $ tools/testing/selftests/vfio/scripts/setup.sh 0000:00:04.0
  $ tools/testing/selftests/vfio/vfio_pci_liveupdate_kexec_test --stage 2 0000:00:04.0
  $ tools/testing/selftests/vfio/scripts/cleanup.sh

It is also possible to run vfio_pci_liveupdate_kexec_test multiple times
to preserve multiple devices simultaneously across a Live Update. This
series has been tested with up to 8 devices concurrently preserved.

Changelog
---------

v2:
 - Rebase on top of linux-next (tag: next-20260115)
 - Add missing EXPORT_SYMBOL_GPLs in LUO (Zhu)
 - Add Missing EXPORT_SYMBOL_GPLs for vfio_device_fops (Zhu)
 - Fix circular dependency between vfio-pci-core and vfio-pci (Zhu)
 - Handle pci=assign-busses (Lukas)
 - Drop driver_override patch (Jason)
 - Use kho_alloc_preserve(), kho_unpreserve_free(), kho_restore_free() (Pasha)
 - Don't access PCI FLB after device initialization (Jason)
 - Fix folio leak in vfio_pci_liveupdate_retrieve() (Alex)
 - Add Documentation (Pasha)

v1: https://lore.kernel.org/kvm/20251126193608.2678510-1-dmat...

rfc: https://lore.kernel.org/kvm/20251018000713.677779-1-vipin...

Cc: Saeed Mahameed <saeedm@nvidia.com>
Cc: Adithya Jayachandran <ajayachandra@nvidia.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: Parav Pandit <parav@nvidia.com>
Cc: Leon Romanovsky <leonro@nvidia.com>
Cc: William Tu <witu@nvidia.com>
Cc: Jacob Pan <jacob.pan@linux.microsoft.com>
Cc: Lukas Wunner <lukas@wunner.de>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Pratyush Yadav <pratyush@kernel.org>
Cc: Samiullah Khawaja <skhawaja@google.com>
Cc: Chris Li <chrisl@kernel.org>
Cc: Josh Hilke <jrhilke@google.com>
Cc: David Rientjes <rientjes@google.com>

[1] https://lore.kernel.org/linux-iommu/20251202230303.101751...

David Matlack (13):
  liveupdate: Export symbols needed by modules
  PCI: Add API to track PCI devices preserved across Live Update
  PCI: Inherit bus numbers from previous kernel during Live Update
  vfio/pci: Notify PCI subsystem about devices preserved across Live
    Update
  vfio: Enforce preserved devices are retrieved via
    LIVEUPDATE_SESSION_RETRIEVE_FD
  vfio/pci: Store incoming Live Update state in struct
    vfio_pci_core_device
  docs: liveupdate: Document VFIO device file preservation
  vfio: selftests: Add Makefile support for TEST_GEN_PROGS_EXTENDED
  vfio: selftests: Add vfio_pci_liveupdate_uapi_test
  vfio: selftests: Expose iommu_modes to tests
  vfio: selftests: Expose low-level helper routines for setting up
    struct vfio_pci_device
  vfio: selftests: Verify that opening VFIO device fails during Live
    Update
  vfio: selftests: Add continuous DMA to vfio_pci_liveupdate_kexec_test

Vipin Sharma (9):
  vfio/pci: Register a file handler with Live Update Orchestrator
  vfio/pci: Preserve vfio-pci device files across Live Update
  vfio/pci: Retrieve preserved device files after Live Update
  vfio/pci: Skip reset of preserved device after Live Update
  selftests/liveupdate: Move luo_test_utils.* into a reusable library
  selftests/liveupdate: Add helpers to preserve/retrieve FDs
  vfio: selftests: Build liveupdate library in VFIO selftests
  vfio: selftests: Initialize vfio_pci_device using a VFIO cdev FD
  vfio: selftests: Add vfio_pci_liveupdate_kexec_test

 Documentation/userspace-api/liveupdate.rst    | 144 ++++++++++
 MAINTAINERS                                   |   1 +
 drivers/pci/Makefile                          |   1 +
 drivers/pci/liveupdate.c                      | 212 +++++++++++++++
 drivers/pci/probe.c                           |  23 +-
 drivers/vfio/device_cdev.c                    |  25 +-
 drivers/vfio/group.c                          |   9 +
 drivers/vfio/pci/Makefile                     |   1 +
 drivers/vfio/pci/vfio_pci.c                   |  11 +-
 drivers/vfio/pci/vfio_pci_core.c              |  24 +-
 drivers/vfio/pci/vfio_pci_liveupdate.c        | 246 +++++++++++++++++
 drivers/vfio/pci/vfio_pci_priv.h              |  16 ++
 drivers/vfio/vfio.h                           |  13 -
 drivers/vfio/vfio_main.c                      |  23 +-
 include/linux/kho/abi/pci.h                   |  55 ++++
 include/linux/kho/abi/vfio_pci.h              |  45 +++
 include/linux/pci.h                           |  47 ++++
 include/linux/vfio.h                          |  58 ++++
 include/linux/vfio_pci_core.h                 |   2 +
 kernel/liveupdate/luo_core.c                  |   1 +
 kernel/liveupdate/luo_file.c                  |   2 +
 tools/testing/selftests/liveupdate/.gitignore |   1 +
 tools/testing/selftests/liveupdate/Makefile   |  14 +-
 .../include/libliveupdate.h}                  |  11 +-
 .../selftests/liveupdate/lib/libliveupdate.mk |  20 ++
 .../{luo_test_utils.c => lib/liveupdate.c}    |  43 ++-
 .../selftests/liveupdate/luo_kexec_simple.c   |   2 +-
 .../selftests/liveupdate/luo_multi_session.c  |   2 +-
 tools/testing/selftests/vfio/Makefile         |  23 +-
 .../vfio/lib/include/libvfio/iommu.h          |   2 +
 .../lib/include/libvfio/vfio_pci_device.h     |   8 +
 tools/testing/selftests/vfio/lib/iommu.c      |   4 +-
 .../selftests/vfio/lib/vfio_pci_device.c      |  60 ++--
 .../vfio/vfio_pci_liveupdate_kexec_test.c     | 256 ++++++++++++++++++
 .../vfio/vfio_pci_liveupdate_uapi_test.c      |  93 +++++++
 35 files changed, 1410 insertions(+), 88 deletions(-)
 create mode 100644 drivers/pci/liveupdate.c
 create mode 100644 drivers/vfio/pci/vfio_pci_liveupdate.c
 create mode 100644 include/linux/kho/abi/pci.h
 create mode 100644 include/linux/kho/abi/vfio_pci.h
 rename tools/testing/selftests/liveupdate/{luo_test_utils.h => lib/include/libliveupdate.h} (80%)
 create mode 100644 tools/testing/selftests/liveupdate/lib/libliveupdate.mk
 rename tools/testing/selftests/liveupdate/{luo_test_utils.c => lib/liveupdate.c} (89%)
 create mode 100644 tools/testing/selftests/vfio/vfio_pci_liveupdate_kexec_test.c
 create mode 100644 tools/testing/selftests/vfio/vfio_pci_liveupdate_uapi_test.c


base-commit: 9b7977f9e39b7768c70c2aa497f04e7569fd3e00
-- 
2.53.0.rc1.225.gd81095ad13-goog