[PATCH 13/13] vfio/mdev: add mdev available instance checking to the core

[Tian, Kevin]

> From: Christoph Hellwig
> Sent: Tuesday, June 28, 2022 1:15 PM
> 
> Many of the mdev drivers use a simple counter for keeping track of the
> available instances. Move this code to the core code and store the counter
> in the mdev_parent. Implement it using correct locking, fixing mdpy.
> 
> Drivers just provide the value in the mdev_driver at registration time
> and the core code takes care of maintaining it and exposing the value in
> sysfs.
> 
> Signed-off-by: Jason Gunthorpe <jgg at nvidia.com>
> [count instances per-parent instead of per-type]
> Signed-off-by: Christoph Hellwig <hch at lst.de>

Reviewed-by: Kevin Tian <kevin.tian at intel.com>