[RFC PATCH v4 00/11] Introduce vfio-pci-core subsystem

[Max Gurtovoy <mgurtovoy@nvidia.com>]

Hi Alex, Cornelia, Jason and Co,

This series split the vfio_pci driver into 2 parts: pci drivers and a
subsystem driver that will also be library of code. The main pci driver,
vfio_pci.ko will be used as before and it will bind to the subsystem
driver vfio_pci_core.ko to register to the VFIO subsystem.

This series is coming to solve some of the issues that were raised in
the previous attempts for extending vfio-pci for vendor specific
functionality:
1. https://lkml.org/lkml/2020/5/17/376 by Yan Zhao.
2. https://www.spinics.net/lists/kernel/msg3903996.html by Longfang Liu

This subsystem framework will also ease on adding new vendor specific
functionality to VFIO devices in the future by allowing another module
to provide the pci_driver that can setup number of details before
registering to VFIO subsystem (such as inject its own operations).

This series also extends the "driver_override" mechanism. We added a flag
for pci drivers that will declare themselves as "driver_override" capable
and only declared drivers can use this mechanism in the PCI subsystem.
Other drivers will not be able to bind to devices that use "driver_override".
Also, the PCI driver matching will always look for ID table and will never
generate dummy "match_all" ID table in the PCI subsystem layer. In this
way, we ensure deterministic behaviour with no races with the original
pci drivers. In order to get the best match for "driver_override" drivers,
one can create a userspace program (example can be found at
https://github.com/maxgurtovoy/linux_tools/blob/main/vfio/bind_vfio_pci_driver.py)
that find the 'best match' according to simple algorithm: "the driver
with the fewest '*' matches wins."
For example, the vfio-pci driver will match to any pci device. So it
will have the maximal '*' matches (for all matching IDs: vendor, device,
subvendor, ...).
In case we are looking for a match to mlx5 based device, we'll have a
match to vfio-pci.ko and mlx5-vfio-pci.ko. We'll prefer mlx5-vfio-pci.ko
since it will have less '*' matches (probably vendor and device IDs will
match). This will work in the future for NVMe/Virtio devices that can
match according to a class code or other criteria.

The main goal of this series is to agree on the vfio_pci module split and the
"driver_override" extensions. The follow-up version will include an extended
mlx5_vfio_pci driver that will support VF suspend/resume as well.

This series applied cleanly on top of vfio reflck re-design (still haven't sent
for review) and can be found at:
https://github.com/Mellanox/NVMEoF-P2P/tree/vfio-v4-external.

Max Gurtovoy (11):
  vfio-pci: rename vfio_pci.c to vfio_pci_core.c
  vfio-pci: rename vfio_pci_private.h to vfio_pci_core.h
  vfio-pci: rename vfio_pci_device to vfio_pci_core_device
  vfio-pci: rename ops functions to fit core namings
  vfio-pci: include vfio header in vfio_pci_core.h
  vfio-pci: introduce vfio_pci.c
  vfio-pci: move igd initialization to vfio_pci.c
  PCI: add flags field to pci_device_id structure
  PCI: add matching checks for driver_override binding
  vfio-pci: introduce vfio_pci_core subsystem driver
  mlx5-vfio-pci: add new vfio_pci driver for mlx5 devices

 Documentation/ABI/testing/sysfs-bus-pci       |    6 +-
 Documentation/PCI/pci.rst                     |    1 +
 drivers/pci/pci-driver.c                      |   22 +-
 drivers/vfio/pci/Kconfig                      |   27 +-
 drivers/vfio/pci/Makefile                     |   12 +-
 drivers/vfio/pci/mlx5_vfio_pci.c              |  130 +
 drivers/vfio/pci/vfio_pci.c                   | 2329 +----------------
 drivers/vfio/pci/vfio_pci_config.c            |   70 +-
 drivers/vfio/pci/vfio_pci_core.c              | 2239 ++++++++++++++++
 drivers/vfio/pci/vfio_pci_igd.c               |   16 +-
 drivers/vfio/pci/vfio_pci_intrs.c             |   42 +-
 drivers/vfio/pci/vfio_pci_rdwr.c              |   18 +-
 drivers/vfio/pci/vfio_pci_zdev.c              |    4 +-
 include/linux/mod_devicetable.h               |    9 +
 include/linux/pci.h                           |   27 +
 .../linux/vfio_pci_core.h                     |   93 +-
 scripts/mod/devicetable-offsets.c             |    1 +
 scripts/mod/file2alias.c                      |    8 +-
 18 files changed, 2695 insertions(+), 2359 deletions(-)
 create mode 100644 drivers/vfio/pci/mlx5_vfio_pci.c
 create mode 100644 drivers/vfio/pci/vfio_pci_core.c
 rename drivers/vfio/pci/vfio_pci_private.h => include/linux/vfio_pci_core.h (56%)

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2.21.0