This addresses Cornelia's remark on the earlier patch that ccw has a confusing lifecycle. While it doesn't seem like the original attempt was functionally wrong, the result can be made better with a lot of further work.
Reorganize the driver so that the mdev owns the private memory and controls the lifecycle, not the css_driver. The memory associated with the css_driver lifecycle is only the mdev_parent/mdev_type registration.
Along the way we change when the sch is quiescent or not to be linked to the open/close_device lifetime of the vfio_device, which is sort of what it was tring to do already, just not completely.
The troublesome racey lifecycle of the css_driver callbacks is made clear with simple vfio_device refcounting so a callback is only delivered into a registered vfio_device and has obvious correctness.
Move the only per-css_driver state, the "available instance" counter, into the core code and share that logic with many of the other drivers. The value is kept in the mdev_type memory.
This is on github: https://github.com/jgunthorpe/linux/commits/vfio_ccw
v3: - Rebase to Christoph's group work & rc3; use vfio_register_emulated_iommu_dev() - Remove GFP_DMA - Order mdev_unregister_driver() symmetrically with init - Rework what is considered a BROKEN event in fsm_close() - NOP both CCW_EVENT_OPEN/CLOSE - Documentation updates - Remane goto label to err_init vfio_ccw_mdev_probe() - Fix NULL pointer deref in mdev_device_create() v2: https://lore.kernel.org/r/0-v2-7d3a384024cf+2060-ccw_mdev_jgg@nvidia.com - Clean up the lifecycle in ccw with 7 new patches - Rebase v1: https://lore.kernel.org/all/7-v2-7667f42c9bad+935-vfio3_jgg@nvidia.com
Jason Gunthorpe (10): vfio/ccw: Remove unneeded GFP_DMA vfio/ccw: Use functions for alloc/free of the vfio_ccw_private vfio/ccw: Pass vfio_ccw_private not mdev_device to various functions vfio/ccw: Convert to use vfio_register_emulated_iommu_dev() vfio/ccw: Make the FSM complete and synchronize it to the mdev vfio/mdev: Consolidate all the device_api sysfs into the core code vfio/mdev: Add mdev available instance checking to the core vfio/ccw: Remove private->mdev vfio: Export vfio_device_try_get() vfio/ccw: Move the lifecycle of the struct vfio_ccw_private to the mdev
.../driver-api/vfio-mediated-device.rst | 8 +- drivers/gpu/drm/i915/gvt/kvmgt.c | 9 +- drivers/s390/cio/vfio_ccw_drv.c | 282 ++++++++---------- drivers/s390/cio/vfio_ccw_fsm.c | 158 +++++++--- drivers/s390/cio/vfio_ccw_ops.c | 240 +++++++-------- drivers/s390/cio/vfio_ccw_private.h | 42 ++- drivers/s390/crypto/vfio_ap_ops.c | 41 +-- drivers/s390/crypto/vfio_ap_private.h | 2 - drivers/vfio/mdev/mdev_core.c | 13 +- drivers/vfio/mdev/mdev_private.h | 2 + drivers/vfio/mdev/mdev_sysfs.c | 64 +++- drivers/vfio/vfio.c | 3 +- include/linux/mdev.h | 13 +- include/linux/vfio.h | 1 + samples/vfio-mdev/mbochs.c | 9 +- samples/vfio-mdev/mdpy.c | 31 +- samples/vfio-mdev/mtty.c | 10 +- 17 files changed, 482 insertions(+), 446 deletions(-)
base-commit: d9a0cd510c3383b61db6f70a84e0c3487f836a63