iommu/amd: Enforce 4k mapping for certain IOMMU data structures

iommu/amd: Enforce 4k mapping for certain IOMMU data structures

AMD IOMMU requires 4k-aligned pages for the event log, the PPR log,
and the completion wait write-back regions. However, when allocating
the pages, they could be part of large mapping (e.g. 2M) page.
This causes #PF due to the SNP RMP hardware enforces the check based
on the page level for these data structures.

So, fix by calling set_memory_4k() on the allocated pages.

Fixes: cb8ae7aef532 ("iommu/amd: Use 4K page for completion wait write-back semaphore")
Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
Cc: Brijesh Singh <brijesh.singh@amd.com>
Link: https://lore.kernel.org/r/20201105145832.3065-1-suravee.suthikulpanit@amd.com
Signed-off-by: Will Deacon <will@kernel.org>