[PATCH v2 1/7] drm/i915: Drop user contexts on driver remove

[Chris Wilson]

Quoting Janusz Krzysztofik (2020-07-06 07:29:05)
> Contexts associated with open device file descriptors together with
> their assigned address spaces are now closed on device file close.
> On address space closure its underlying DMA mappings are revoked.
> When the device is removed while being open, DMA API may then issue
> a warning on device associated DMA mappings still active.  Moreover,
> subsequent attempts to revoke those mappings while late closing the
> device file descriptor may be judged by intel-iommu code as bugs and
> result in kernel panic.

As I said originally, you are tackling this at the wrong layer, as
evidenced imo by that you need multiple patches to do the same thing and
you still haven't found all the places that hold dma/iommu mappings --
because they are not tracked on behalf of a user.
-Chris