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

JIRA: https://issues.redhat.com/browse/RHEL-40162
Upstream Status: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git

commit dceb530
Author: Joao Martins <joao.m.martins@oracle.com>
Date:   Thu Jun 27 12:00:59 2024 +0100

    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>

(cherry picked from commit dceb530)
Signed-off-by: Jerry Snitselaar <jsnitsel@redhat.com>

Author: snits

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;