vfio: Split creation of a vfio_device into init and register ops

[ Upstream commit 0bfc6a4ea63c2adac71a824397ef48f28dbc5e47 ]

This makes the struct vfio_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_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(dev, 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 vfio_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>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Reviewed-by: Max Gurtovoy <mgurtovoy@nvidia.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Message-Id: <3-v3-225de1400dfc+4e074-vfio1_jgg@nvidia.com>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

1 files changed, 16 insertions, 0 deletions

diff --git a/include/linux/vfio.h b/include/linux/vfio.h
index 38d3c6a8dc7e..f479c5d7f2c3 100644
--- a/include/linux/vfio.h
+++ b/include/linux/vfio.h
@@ -15,6 +15,18 @@
 #include <linux/poll.h>
 #include <uapi/linux/vfio.h>
 
+struct vfio_device {
+	struct device *dev;
+	const struct vfio_device_ops *ops;
+	struct vfio_group *group;
+
+	/* Members below here are private, not for driver use */
+	refcount_t refcount;
+	struct completion comp;
+	struct list_head group_next;
+	void *device_data;
+};
+
 /**
  * struct vfio_device_ops - VFIO bus driver device callbacks
  *
@@ -48,11 +60,15 @@ struct vfio_device_ops {
 extern struct iommu_group *vfio_iommu_group_get(struct device *dev);
 extern void vfio_iommu_group_put(struct iommu_group *group, struct device *dev);
 
+void vfio_init_group_dev(struct vfio_device *device, struct device *dev,
+			 const struct vfio_device_ops *ops, void *device_data);
+int vfio_register_group_dev(struct vfio_device *device);
 extern int vfio_add_group_dev(struct device *dev,
 			      const struct vfio_device_ops *ops,
 			      void *device_data);
 
 extern void *vfio_del_group_dev(struct device *dev);
+void vfio_unregister_group_dev(struct vfio_device *device);
 extern struct vfio_device *vfio_device_get_from_dev(struct device *dev);
 extern void vfio_device_put(struct vfio_device *device);
 extern void *vfio_device_data(struct vfio_device *device);