intel-iommu: Document iova_tree
It seems not super clear on when iova_tree is used, and why. Add a rich
comment above iova_tree to track why we needed the iova_tree, and when we
need it.
Also comment for the map/unmap messages, on how they're used and
implications (e.g. unmap can be larger than the mapped ranges).
Suggested-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
Message-Id: <
20230109193727.
1360190-1-peterx@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>