On Fri, Oct 01, 2021 at 02:52:41PM -0300, Jason Gunthorpe wrote:

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 (local)
 - 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 (local)

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()

IBM folks, what do you want to do with this? I would like to go ahead
with these patches so we can get closer to unblocking some of the VFIO
core work.

These patches:

  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

Where made to show how to structure this more cleanly as Cornelia
asked but are not essential and IBMers could test and fix to get this
cleanup when time permits..

Thoughts?

Thanks,
Jason