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

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[ 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>
This commit is contained in:
Jason Gunthorpe
2021-03-30 09:53:05 -06:00
committed by Greg Kroah-Hartman
parent f54fa910e6
commit a2fbf4acd2
3 changed files with 97 additions and 71 deletions
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27
Documentation/driver-api/vfio.rst
View File

@@ -249,18 +249,23 @@ VFIO bus driver API
VFIO bus drivers, such as vfio-pci make use of only a few interfaces
into VFIO core. When devices are bound and unbound to the driver,
the driver should call vfio_add_group_dev() and vfio_del_group_dev()
respectively::
the driver should call vfio_register_group_dev() and
vfio_unregister_group_dev() respectively::
extern int vfio_add_group_dev(struct device *dev,
const struct vfio_device_ops *ops,
void *device_data);
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);
void vfio_unregister_group_dev(struct vfio_device *device);
extern void *vfio_del_group_dev(struct device *dev);
vfio_add_group_dev() indicates to the core to begin tracking the
iommu_group of the specified dev and register the dev as owned by
a VFIO bus driver. The driver provides an ops structure for callbacks
The driver should embed the vfio_device in its own structure and call
vfio_init_group_dev() to pre-configure it before going to registration.
vfio_register_group_dev() indicates to the core to begin tracking the
iommu_group of the specified dev and register the dev as owned by a VFIO bus
driver. Once vfio_register_group_dev() returns it is possible for userspace to
start accessing the driver, thus the driver should ensure it is completely
ready before calling it. The driver provides an ops structure for callbacks
similar to a file operations structure::
struct vfio_device_ops {
@@ -276,7 +281,7 @@ similar to a file operations structure::
};
Each function is passed the device_data that was originally registered
in the vfio_add_group_dev() call above. This allows the bus driver
in the vfio_register_group_dev() call above. This allows the bus driver
an easy place to store its opaque, private data. The open/release
callbacks are issued when a new file descriptor is created for a
device (via VFIO_GROUP_GET_DEVICE_FD). The ioctl interface provides