On Tue, 9 Mar 2021 17:38:42 -0400 Jason Gunthorpe <jgg@xxxxxxxxxx> wrote: > This series: > > The main focus of this series is to make VFIO follow the normal kernel > convention of structure embedding for structure inheritance instead of > linking using a 'void *opaque'. Here we focus on moving the vfio_device to > be a member of every struct vfio_XX_device that is linked by a > vfio_add_group_dev(). > > In turn this allows 'struct vfio_device *' to be used everwhere, and the > public API out of vfio.c can be cleaned to remove places using 'struct > device *' and 'void *' as surrogates to refer to the device. > > While this has the minor trade off of moving 'struct vfio_device' the > clarity of the design is worth it. I can speak directly to this idea, as > I've invested a fair amount of time carefully working backwards what all > the type-erased APIs are supposed to be and it is certainly not trivial or > intuitive. > > When we get into mdev land things become even more inscrutable, and while > I now have a pretty clear picture, it was hard to obtain. I think this > agrees with the kernel style ideal of being explicit in typing and not > sacrificing clarity to create opaque structs. > > After this series the general rules are: > - Any vfio_XX_device * can be obtained at no cost from a vfio_device * > using container_of(), and the reverse is possible by &XXdev->vdev > > This is similar to how 'struct pci_device' and 'struct device' are > interrelated. > > This allows 'device_data' to be completely removed from the vfio.c API. > > - The drvdata for a struct device points at the vfio_XX_device that > belongs to the driver that was probed. drvdata is removed from the core > code, and only used as part of the implementation of the struct > device_driver. > > - The lifetime of vfio_XX_device and vfio_device are identical, they are > the same memory. > > This follows the existing model where vfio_del_group_dev() blocks until > all vfio_device_put()'s are completed. This in turn means the struct > device_driver remove() blocks, and thus under the driver_lock() a bound > driver must have a valid drvdata pointing at both vfio device > structs. A following series exploits this further. > > Most vfio_XX_device structs have data that duplicates the 'struct > device *dev' member of vfio_device, a following series removes that > duplication too. > > Jason > > Jason Gunthorpe (10): > vfio: Simplify the lifetime logic for vfio_device > vfio: Split creation of a vfio_device into init and register ops > vfio/platform: Use vfio_init/register/unregister_group_dev > vfio/fsl-mc: Use vfio_init/register/unregister_group_dev > vfio/pci: Use vfio_init/register/unregister_group_dev > vfio/mdev: Use vfio_init/register/unregister_group_dev > vfio/mdev: Make to_mdev_device() into a static inline > vfio: Make vfio_device_ops pass a 'struct vfio_device *' instead of > 'void *' > vfio/pci: Replace uses of vfio_device_data() with container_of > vfio: Remove device_data from the vfio bus driver API > > Documentation/driver-api/vfio.rst | 48 ++-- > drivers/vfio/fsl-mc/vfio_fsl_mc.c | 69 +++--- > drivers/vfio/fsl-mc/vfio_fsl_mc_private.h | 1 + > drivers/vfio/mdev/mdev_private.h | 5 +- > drivers/vfio/mdev/vfio_mdev.c | 57 +++-- > drivers/vfio/pci/vfio_pci.c | 109 +++++---- > drivers/vfio/pci/vfio_pci_private.h | 1 + > drivers/vfio/platform/vfio_amba.c | 8 +- > drivers/vfio/platform/vfio_platform.c | 21 +- > drivers/vfio/platform/vfio_platform_common.c | 56 ++--- > drivers/vfio/platform/vfio_platform_private.h | 5 +- > drivers/vfio/vfio.c | 210 ++++++------------ > include/linux/vfio.h | 37 +-- > 13 files changed, 299 insertions(+), 328 deletions(-) > This looks great. As Christoph noted, addressing those init vs register races in the bus drivers don't seem too difficult or out of scope for this series. Thanks, Alex
