tree 486a0a42f1d0468a7e640c4e8517d5226d5a5306
parent 2ea659a9ef488125eb46da6eb571de5eae5c43f6
author Robin Murphy <robin.murphy@arm.com> 1494934008 +0100
committer Joerg Roedel <jroedel@suse.de> 1495028055 +0200

iommu/iova: Sort out rbtree limit_pfn handling

When walking the rbtree, the fact that iovad->start_pfn and limit_pfn
are both inclusive limits creates an ambiguity once limit_pfn reaches
the bottom of the address space and they overlap. Commit 5016bdb796b3
("iommu/iova: Fix underflow bug in __alloc_and_insert_iova_range") fixed
the worst side-effect of this, that of underflow wraparound leading to
bogus allocations, but the remaining fallout is that any attempt to
allocate start_pfn itself erroneously fails.

The cleanest way to resolve the ambiguity is to simply make limit_pfn an
exclusive limit when inside the guts of the rbtree. Since we're working
with PFNs, representing one past the top of the address space is always
possible without fear of overflow, and elsewhere it just makes life a
little more straightforward.

Reported-by: Aaron Sierra <asierra@xes-inc.com>
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>