Bug#990279: 9a89a721b41b (" drm/amdgpu: check alignment on CPU page for bo map") breaks amdgpu on ppc64 machines?

[Nathaniel Filardo <nwfilardo@gmail.com>]

It occurs to me, quite belatedly, that it may be worth asking the
author, reviewers, and signers of the change in question their
thoughts on this bug report:
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=990279

In particular, on ppc64 systems, Linux typically is configured to use
a 64KiB page (i.e., shift 16) rather than 4KiB (shift 12) page.  It
looks, however, that AMDGPU_GPU_PAGE_SIZE is always 4096, and so
something (perhaps in userspace, even, eek?) is requesting
4KiB-but-not-64KiB alignment of this buffer.

Any insight you could offer would be deeply appreciated.
Thanks,
--nwf;