On Thu, Jul 8, 2021 at 6:44 PM Andi Kleen [off-list ref] wrote:

quoted

One allocation for the life of the driver that can have its direct map
permissions changed rather than an allocation per-file descriptor and
fragmenting the direct map.

The vmap() approach discussed in another mail will solve that.

Ok, not my first choice for how to handle the allocation side of that,
but not broken.

I'd still feel better if there was an actual data structure assigned
to file->private_data rather than using that 'void *' pointer directly
and casting throughout the driver.