Re: [PATCH v2 03/14] vfio: Split creation of a vfio_device into init and register ops
From: Cornelia Huck <cohuck@redhat.com>
Date: 2021-03-16 12:26:58
Also in:
kvm
On Fri, 12 Mar 2021 20:55:55 -0400 Jason Gunthorpe [off-list ref] 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 gos/vifo_device/vfio_device/
quoted hunk ↗ jump to hunk
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 <redacted> 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(-)diff --git a/Documentation/driver-api/vfio.rst b/Documentation/driver-api/vfio.rst index f1a4d3c3ba0bb1..d3a02300913a7f 100644 --- a/Documentation/driver-api/vfio.rst +++ b/Documentation/driver-api/vfio.rst@@ -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:: - - 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); - -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 call vfio_register_group_dev() and +vfio_unregister_group_dev() respectively:: + + 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); + +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.
s/it/that structure/ (I guess?)
+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 {Reviewed-by: Cornelia Huck <cohuck@redhat.com>