[PATCH v3 00/24] vfio/pci: Base Live Update support for VFIO device files

[David Matlack <dmatlack@google.com>]

This series can be found on GitHub:

  https://github.com/dmatlack/linux/tree/liveupdate/vfio/cdev/v3

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:

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

Steps 1 and 2 are already in-progress on the mailing list. We are
working on a detailed roadmap for steps 3 and 4.

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.

Dependencies
------------

This series is built on top of v7.0-rc4 plus a series from Pasha
Tatashin to fix the module refcounting in FLB:

  https://lore.kernel.org/lkml/20260318141637.1870220-10-pasha.tatashin@soleen.com/

Changelog
---------

v3:
 - Add logging & documentation for pci=assign-busses overrides (Pranjal)
 - Use 2026 in drivers/pci/liveupdate.c (Pranjal)
 - Use 2026 in drivers/vfio/pci/vfio_pci_liveupdate.c (Pranjal)
 - Drop incoming/outgoing from PCI APIs (Sami)
 - Eliminate duplicate extern declarations for vfio_device_fops
   (Pranjal)
 - Keep struct vfio_device_file private (Pranjal)
 - Add comment about not supporting hot-plug (Pranjal)
 - Add comment about not supporting VFs (Sami)
 - Better error handling for liveupdate_flb_get_incoming() (Pranjal)
 - Remove liveupdate_enabled() checks (Zhu)
 - Remove liveupdate_enabled() checks in vfio_pci_liveupdate_init() (Pranjal)
 - Drop IOMMU reference from bus number commit message (Bjorn)
 - Add fabric rationale to commit message (Jason)
 - Swap incoming ... outgoing ordering in commit message (Bjorn)
 - Use vfio_device_cdev_opened() instead of df->group (Alex)
 - Add comments for CONFIG_VFIO_PCI_ZDEV_KVM (Alex)
 - Add comments for vfio_pci_is_intel_display() (Alex)
 - Use pci_dev_try_lock() in freeze (Alex)
 - Fix device reset locking in freeze() (me)
 - Use u32 for domain in PCI (Bjorn)
 - Use u32 for domain in VFIO (Bjorn)
 - Make pci_liveupdate_incoming_nr_devices() private to drivers/pci/ (Bjorn)
 - Fix dev->liveupdate_incoming readability (Bjorn)
 - Take pci_ser_delete() out of WARN_ON_ONCE() (Bjorn)
 - Drop reference to userspace & files from PCI commit message (Bjorn)
 - Rename __vfio_device_fops_cdev_open() to vfio_device_cdev_open_file() (Alex)
 - Fix NULL pointer dereference in release() (Alex)
 - Handle return value of pci_liveupdate_outgoing_preserve() (Alex)
 - Make pci_liveupdate_unregister_fh() unabe to fail. (Alex)
 - Move vfio_liveupdate_incoming_is_preserved() to drivers/vfio/vfio.h (Alex)
 - Add vfio_pci_core_probe_reset() (Alex)
 - Forward declare ser struct in include/linux/vfio_pci_core.h (Alex)
 - Bump compatibility string when adding reset_works (Alex)
 - How will userspace detect partial preservation? (Alex)
 - Require single device per iommu_group (Jason)
 - Rename pci_liveupdate_register_fh() to pci_liveupdate_register_flb() (Vipin)
 - Use ksft_exit_skip() and SKIP() (Vipin)
 - Move documentation to code (Vipin)
 - Use __u64 instead of int for token in Live Update selftest helpers (Gemini)
 - Add documentation for drivers/pci/liveupdate.c (me)

v2: https://lore.kernel.org/kvm/20260129212510.967611-1-dmatlack@google.com/

v1: https://lore.kernel.org/kvm/20251126193608.2678510-1-dmatlack@google.com/

rfc: https://lore.kernel.org/kvm/20251018000713.677779-1-vipinsh@google.com/

Cc: Pranjal Shrivastava <praan@google.com>
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/20251202230303.1017519-1-skhawaja@google.com/

David Matlack (15):
  liveupdate: Export symbols needed by modules
  PCI: Add API to track PCI devices preserved across Live Update
  PCI: Require Live Update preserved devices are in singleton
    iommu_groups
  PCI: Inherit bus numbers from previous kernel during Live Update
  docs: liveupdate: Add documentation for PCI
  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: Add documentation for VFIO PCI
  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/PCI/liveupdate.rst              |  23 +
 .../admin-guide/kernel-parameters.txt         |   6 +-
 Documentation/core-api/liveupdate.rst         |   2 +
 .../driver-api/vfio_pci_liveupdate.rst        |  23 +
 MAINTAINERS                                   |   2 +
 drivers/pci/Kconfig                           |  11 +
 drivers/pci/Makefile                          |   1 +
 drivers/pci/liveupdate.c                      | 415 ++++++++++++++++++
 drivers/pci/pci.h                             |  14 +
 drivers/pci/probe.c                           |  37 +-
 drivers/vfio/device_cdev.c                    |  63 ++-
 drivers/vfio/group.c                          |   9 +
 drivers/vfio/pci/Kconfig                      |  11 +
 drivers/vfio/pci/Makefile                     |   1 +
 drivers/vfio/pci/vfio_pci.c                   |  14 +-
 drivers/vfio/pci/vfio_pci_core.c              |  90 ++--
 drivers/vfio/pci/vfio_pci_liveupdate.c        | 328 ++++++++++++++
 drivers/vfio/pci/vfio_pci_priv.h              |  18 +
 drivers/vfio/vfio.h                           |  18 +
 drivers/vfio/vfio_main.c                      |  16 +-
 include/linux/kho/abi/pci.h                   |  62 +++
 include/linux/kho/abi/vfio_pci.h              |  45 ++
 include/linux/pci.h                           |  41 ++
 include/linux/vfio.h                          |  13 +
 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 ++++
 41 files changed, 1715 insertions(+), 92 deletions(-)
 create mode 100644 Documentation/PCI/liveupdate.rst
 create mode 100644 Documentation/driver-api/vfio_pci_liveupdate.rst
 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: 3251ac3df4374e4e94e4fbecf49ad1573933018a
prerequisite-patch-id: 37ebd38e2247ccb02e6a6c7543a378534d69a038
prerequisite-patch-id: 19c8469a9ae5cd13618481dd75012444330f80f9
prerequisite-patch-id: 2ba04f598993e2c2d941c4cd3f2dc1e98905d68b
prerequisite-patch-id: fcab928f6ee32a145667822ceca5e4f1f567d530
prerequisite-patch-id: 6d11347278609426baa9eacc1726b32b48d09a25
prerequisite-patch-id: 94a9e8a8cb6004e12de90fcc0068e8a8b12652de
prerequisite-patch-id: d658019a7ac7c82ebe4a6c6086457e27460174d3
prerequisite-patch-id: 41e68c9fc8e8c5e493497e87ca13577b3167cf80
-- 
2.53.0.983.g0bb29b3bc5-goog