iommufd/selftest: Do not record head iova to better match iommu drivers

Do not set a hugepage-aligned IOVA for incrementing an IOVA, to better
match current IOMMU driver implementations. Keep the logic of clearing all
IOPTE dirty bits for a whole hugepage, even if the range being dirtied
starts from part of the hugepage. This is also similar to AMD driver (iommu
v1 format) where IOMMU uses various subpage PTE data for dirty tracking
(for non-standard page sizes).

Link: https://lore.kernel.org/r/20240627110105.62325-6-joao.m.martins@oracle.com
Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Tested-by: Matt Ochs <mochs@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

drivers/iommu/iommufd/selftest.c

@@ -266,8 +266,8 @@ static int mock_domain_read_and_clear_dirty(struct iommu_domain *domain,
 
 		/* Clear dirty */
 		if (mock_test_and_clear_dirty(mock, head, pgsize, flags))
-			iommu_dirty_bitmap_record(dirty, head, pgsize);
-		iova = head + pgsize;
+			iommu_dirty_bitmap_record(dirty, iova, pgsize);
+		iova += pgsize;
 	} while (iova < end);
 
 	return 0;