Excerpts from Ian Munsie's message of 2014-12-08 19:18:01 +1100:

From: Ian Munsie <redacted>

If we need to force detach a context (e.g. due to EEH or simply force
unbinding the driver) we should prevent the userspace contexts from
being able to access the Problem State Area MMIO region further, which
they may have mapped with mmap().

This patch unmaps any mapped MMIO regions when detaching a userspace
context.

Might want to drop this one for now - Philippe found that it sometimes
causes an issue when multiple contexts are using the afu. Seems that
unmap_mapping_range() unmapped a bit more than I expected.

Cheers,
-Ian