+ /*
+ * vfio-iommu-type1 (v1) - User mappings were coalesced together to
+ * avoid tracking individual mappings. This means that the granularity
+ * of the original mapping was lost and the user was allowed to attempt
+ * to unmap any range. Depending on the contiguousness of physical
+ * memory and page sizes supported by the IOMMU, arbitrary unmaps may
+ * or may not have worked. We only guaranteed unmap granularity
+ * matching the original mapping; even though it was untracked here,
+ * the original mappings are reflected in IOMMU mappings. This
+ * resulted in a couple unusual behaviors. First, if a range is not
+ * able to be unmapped, ex. a set of 4k pages that was mapped as a
+ * 2M hugepage into the IOMMU, the unmap ioctl returns success but with
+ * a zero sized unmap. Also, if an unmap request overlaps the first
+ * address of a hugepage, the IOMMU will unmap the entire hugepage.
+ * This also returns success and the returned unmap size reflects the
+ * actual size unmapped.
+ *
+ * We attempt to maintain compatibility with this "v1" interface, but
+ * we take control out of the hands of the IOMMU. Therefore, an unmap
+ * request offset from the beginning of the original mapping will
+ * return success with zero sized unmap. And an unmap request covering
+ * the first iova of mapping will unmap the entire range.
+ *
+ * The v2 version of this interface intends to be more deterministic.
+ * Unmap requests must fully cover previous mappings. Multiple
+ * mappings may still be unmaped by specifying large ranges, but there
+ * must not be any previous mappings bisected by the range. An error
+ * will be returned if these conditions are not met. The v2 interface
+ * will only return success and a size of zero if there were no
+ * mappings within the range.
+ */
+ if (iommu->v2) {
+ dma = vfio_find_dma(iommu, unmap->iova, 0);
+ if (dma && dma->iova != unmap->iova) {
+ ret = -EINVAL;
+ goto unlock;
+ }
+ dma = vfio_find_dma(iommu, unmap->iova + unmap->size - 1, 0);
+ if (dma && dma->iova + dma->size != unmap->iova + unmap->size) {
+ ret = -EINVAL;
+ goto unlock;
+ }
+ }
+