Re: [PATCH 00/12] Introduce vfio_pci_core subsystem

On Wed, 4 Aug 2021 16:41:34 +0300
Yishai Hadas [off-list ref] wrote:

On 7/21/2021 7:15 PM, Yishai Hadas wrote:

quoted

Prologue:

This is the second series of three to send the "mlx5_vfio_pci" driver
that has been discussed on the list for a while now. It comes on top of
the first series (i.e. Reorganize reflck to support splitting vfio_pci)
that was sent already and pending merge [1].

  - Split vfio_pci into vfio_pci/vfio_pci_core and provide infrastructure
    for non-generic VFIO PCI drivers.
  - The new driver mlx5_vfio_pci that is a full implementation of
    suspend/resume functionality for mlx5 devices.

A preview of all the patches can be seen here:
https://github.com/jgunthorpe/linux/commits/mlx5_vfio_pci

[1] https://lore.kernel.org/dri-devel/0-v2-b6a5582525c9+ff96-vfio_reflck_jgg@nvidia.com/T/#t (local)
=====================

 From Max Gurtovoy:
====================
This series splits the vfio_pci driver into two parts, a PCI driver and
a subsystem driver that will also be library of code. The main PCI
driver, vfio_pci.ko, will remain as before and it will use the library
module vfio_pci_core.ko to help create the vfio_device.

This series is intended to solve the issues that were raised in the
previous attempts for extending vfio-pci for device specific
functionality:

1. https://lore.kernel.org/kvm/20200518024202.13996-1-yan.y.zhao@intel.com (local)
    by Yan Zhao
2. https://lore.kernel.org/kvm/20210702095849.1610-1-shameerali.kolothum.thodi@huawei.com (local)
    by Longfang Liu

Also to support proposed future changes to virtio and other common
protocols to support migration:

https://lists.oasis-open.org/archives/virtio-comment/202106/msg00044.html

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

This series also extends the "driver_override" mechanism. A flag is
added for PCI drivers that will declare themselves as "driver_override"
capable which sends their match table to the modules.alias file but
otherwise leaves them outside of the normal driver core auto-binding
world, like vfio_pci.

In order to get the best match for "driver_override" drivers, one can
create a userspace program to inspect the modules.alias, an example can
be found at:

https://github.com/maxgurtovoy/linux_tools/blob/main/vfio/bind_vfio_pci_driver.py

Which finds the 'best match' according to a 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.

In case we are looking for a match to a 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.

Yishai


Jason Gunthorpe (2):
   vfio: Use select for eventfd
   vfio: Use kconfig if XX/endif blocks instead of repeating 'depends on'

Max Gurtovoy (9):
   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: Split the pci_driver code out of vfio_pci_core.c
   vfio/pci: Move igd initialization to vfio_pci.c
   PCI: Add a PCI_ID_F_VFIO_DRIVER_OVERRIDE flag to struct pci_device_id
   vfio/pci: Introduce vfio_pci_core.ko

Yishai Hadas (1):
   vfio/pci: Move module parameters to vfio_pci.c

  Documentation/PCI/pci.rst                     |    1 +
  drivers/pci/pci-driver.c                      |   25 +-
  drivers/vfio/Kconfig                          |   29 +-
  drivers/vfio/fsl-mc/Kconfig                   |    3 +-
  drivers/vfio/mdev/Kconfig                     |    1 -
  drivers/vfio/pci/Kconfig                      |   39 +-
  drivers/vfio/pci/Makefile                     |    8 +-
  drivers/vfio/pci/vfio_pci.c                   | 2238 +----------------
  drivers/vfio/pci/vfio_pci_config.c            |   70 +-
  drivers/vfio/pci/vfio_pci_core.c              | 2138 ++++++++++++++++
  drivers/vfio/pci/vfio_pci_igd.c               |   19 +-
  drivers/vfio/pci/vfio_pci_intrs.c             |   42 +-
  drivers/vfio/pci/vfio_pci_rdwr.c              |   18 +-
  drivers/vfio/pci/vfio_pci_zdev.c              |    4 +-
  drivers/vfio/platform/Kconfig                 |    6 +-
  drivers/vfio/platform/reset/Kconfig           |    4 +-
  include/linux/mod_devicetable.h               |    7 +
  include/linux/pci.h                           |   27 +
  .../linux/vfio_pci_core.h                     |   89 +-
  scripts/mod/devicetable-offsets.c             |    1 +
  scripts/mod/file2alias.c                      |    8 +-
  21 files changed, 2496 insertions(+), 2281 deletions(-)
  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%)
 

Hi Alex,

Based on the feedback that we got so far on this series, no functional 
changes are expected in V2.

It may include the below minor changes:

- Drop DRIVER_VERSION as it's useless and not required any more. 
(Patches #6, #12).

- Add the sequence of commands/algorithm that is required by userspace 
to discover the matching driver to the commit message of patch #9.

Do we need to wait for more feedback or that we are fine to send V2 ?

 - Resolve Kconfig compatibility in patch 12

Patch 9 also depends on an ack from Bjorn, so whether you want to try
to get his buy-in before or after that patch gets updated to clarify
what it's trying to do and why, is up to you.  Thanks,

Alex