iommufd/selftest: Add tests for <= u8 bitmap sizes

Add more tests for bitmaps smaller than or equal to an u8, though skip the
tests if the IOVA buffer size is smaller than the mock page size.

Link: https://lore.kernel.org/r/20240627110105.62325-4-joao.m.martins@oracle.comSigned-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>

tools/testing/selftests/iommu/iommufd.c

@@ -1727,6 +1727,12 @@ FIXTURE_SETUP(iommufd_dirty_tracking)
 	void *vrc;
 	int rc;
 
+	if (variant->buffer_size < MOCK_PAGE_SIZE) {
+		SKIP(return,
+		     "Skipping buffer_size=%lu, less than MOCK_PAGE_SIZE=%lu",
+		     variant->buffer_size, MOCK_PAGE_SIZE);
+	}
+
 	self->fd = open("/dev/iommu", O_RDWR);
 	ASSERT_NE(-1, self->fd);
 
@@ -1779,6 +1785,18 @@ FIXTURE_TEARDOWN(iommufd_dirty_tracking)
 	teardown_iommufd(self->fd, _metadata);
 }
 
+FIXTURE_VARIANT_ADD(iommufd_dirty_tracking, domain_dirty8k)
+{
+	/* half of an u8 index bitmap */
+	.buffer_size = 8UL * 1024UL,
+};
+
+FIXTURE_VARIANT_ADD(iommufd_dirty_tracking, domain_dirty16k)
+{
+	/* one u8 index bitmap */
+	.buffer_size = 16UL * 1024UL,
+};
+
 FIXTURE_VARIANT_ADD(iommufd_dirty_tracking, domain_dirty128k)
 {
 	/* one u32 index bitmap */