Re: [PATCH v2 03/14] vfio: Split creation of a vfio_device into init and register ops

[Max Gurtovoy <mgurtovoy@nvidia.com>]

On 3/13/2021 2:55 AM, Jason Gunthorpe wrote:
> This makes the struct vfio_pci_device part of the public interface so it
> can be used with container_of and so forth, as is typical for a Linux
> subystem.
>
> This is the first step to bring some type-safety to the vfio interface by
> allowing the replacement of 'void *' and 'struct device *' inputs with a
> simple and clear 'struct vfio_pci_device *'
>
> For now the self-allocating vfio_add_group_dev() interface is kept so each
> user can be updated as a separate patch.
>
> The expected usage pattern is
>
>    driver core probe() function:
>       my_device = kzalloc(sizeof(*mydevice));
>       vfio_init_group_dev(&my_device->vdev, dev, ops, mydevice);
>       /* other driver specific prep */
>       vfio_register_group_dev(&my_device->vdev);
>       dev_set_drvdata(my_device);
>
>    driver core remove() function:
>       my_device = dev_get_drvdata(dev);
>       vfio_unregister_group_dev(&my_device->vdev);
>       /* other driver specific tear down */
>       kfree(my_device);
>
> Allowing the driver to be able to use the drvdata and vifo_device to go
> to/from its own data.
>
> The pattern also makes it clear that vfio_register_group_dev() must be
> last in the sequence, as once it is called the core code can immediately
> start calling ops. The init/register gap is provided to allow for the
> driver to do setup before ops can be called and thus avoid races.
>
> Reviewed-by: Christoph Hellwig <hch@lst.de>
> Reviewed-by: Liu Yi L <yi.l.liu@intel.com>
> Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
> ---
>   Documentation/driver-api/vfio.rst |  31 ++++----
>   drivers/vfio/vfio.c               | 123 ++++++++++++++++--------------
>   include/linux/vfio.h              |  16 ++++
>   3 files changed, 98 insertions(+), 72 deletions(-)

With comments from Cornelia and Kevin, looks good.

Reviewed-by: Max Gurtovoy <mgurtovoy@nvidia.com>