Re: [PATCH 00/22] vfio: Give VFIO_DEVICE_GET_REGION_INFO its own op

[Mostafa Saleh <smostafa@google.com>]

On Thu, Oct 23, 2025 at 08:09:14PM -0300, Jason Gunthorpe wrote:
> There is alot of duplicated code in the drivers for processing
> VFIO_DEVICE_GET_REGION_INFO. Introduce a new op get_region_info_caps()
> which provides a struct vfio_info_cap and handles the cap chain logic
> to write the caps back to userspace and remove all of this duplication
> from drivers.
> 
> This is done in two steps, the first is a largely mechanical introduction
> of the get_region_info(). These patches are best viewed with the diff
> option to ignore whitespace (-b) as most of the lines are re-indending
> things.
> 
> Then drivers are updated to remove the duplicate cap related code. Some
> drivers are converted to use vfio_info_add_capability() instead of open
> coding a version of it.

The series as a whole looks good.
However, I got confused walking through it as almost all non-PCI drivers
had to transition to get_region_info then get_region_info_caps then
removing get_region_info completely from core code after introducing
it in this series.

IMO, the series should start with just consolidating PCI based implementation
and then add get_region_info_caps for all drivers at the end.
Anyway, no really strong opinion as the final outcome makes sense.

Thanks,
Mostafa

> 
> This is on github: https://github.com/jgunthorpe/linux/commits/vfio_get_region_info_op
> 
> Jason Gunthorpe (22):
>   vfio: Provide a get_region_info op
>   vfio/hisi: Convert to the get_region_info op
>   vfio/virtio: Convert to the get_region_info op
>   vfio/nvgrace: Convert to the get_region_info op
>   vfio/pci: Fill in the missing get_region_info ops
>   vfio/mtty: Provide a get_region_info op
>   vfio/mdpy: Provide a get_region_info op
>   vfio/mbochs: Provide a get_region_info op
>   vfio/platform: Provide a get_region_info op
>   vfio/fsl: Provide a get_region_info op
>   vfio/cdx: Provide a get_region_info op
>   vfio/ccw: Provide a get_region_info op
>   vfio/gvt: Provide a get_region_info op
>   vfio: Require drivers to implement get_region_info
>   vfio: Add get_region_info_caps op
>   vfio/mbochs: Convert mbochs to use vfio_info_add_capability()
>   vfio/gvt: Convert to get_region_info_caps
>   vfio/ccw: Convert to get_region_info_caps
>   vfio/pci: Convert all PCI drivers to get_region_info_caps
>   vfio/platform: Convert to get_region_info_caps
>   vfio: Move the remaining drivers to get_region_info_caps
>   vfio: Remove the get_region_info op
> 
>  drivers/gpu/drm/i915/gvt/kvmgt.c              | 272 ++++++++----------
>  drivers/s390/cio/vfio_ccw_ops.c               |  45 +--
>  drivers/vfio/cdx/main.c                       |  29 +-
>  drivers/vfio/fsl-mc/vfio_fsl_mc.c             |  43 ++-
>  .../vfio/pci/hisilicon/hisi_acc_vfio_pci.c    |  54 ++--
>  drivers/vfio/pci/mlx5/main.c                  |   1 +
>  drivers/vfio/pci/nvgrace-gpu/main.c           |  53 +---
>  drivers/vfio/pci/pds/vfio_dev.c               |   1 +
>  drivers/vfio/pci/qat/main.c                   |   1 +
>  drivers/vfio/pci/vfio_pci.c                   |   1 +
>  drivers/vfio/pci/vfio_pci_core.c              | 110 +++----
>  drivers/vfio/pci/virtio/common.h              |   5 +-
>  drivers/vfio/pci/virtio/legacy_io.c           |  38 +--
>  drivers/vfio/pci/virtio/main.c                |   5 +-
>  drivers/vfio/platform/vfio_amba.c             |   1 +
>  drivers/vfio/platform/vfio_platform.c         |   1 +
>  drivers/vfio/platform/vfio_platform_common.c  |  40 ++-
>  drivers/vfio/platform/vfio_platform_private.h |   3 +
>  drivers/vfio/vfio_main.c                      |  45 +++
>  include/linux/vfio.h                          |   4 +
>  include/linux/vfio_pci_core.h                 |   3 +
>  samples/vfio-mdev/mbochs.c                    |  71 ++---
>  samples/vfio-mdev/mdpy.c                      |  34 +--
>  samples/vfio-mdev/mtty.c                      |  33 +--
>  24 files changed, 363 insertions(+), 530 deletions(-)
> 
> 
> base-commit: 211ddde0823f1442e4ad052a2f30f050145ccada
> -- 
> 2.43.0
>