s390/pci: ensure to not cross a dma segment boundary

When we use the iommu_area_alloc helper to get dma addresses
we specify the boundary_size parameter but not the offset (called
shift in this context).

As long as the offset (start_dma) is a multiple of the boundary
we're ok (on current machines start_dma always seems to be 4GB).

Don't leave this to chance and specify the offset for iommu_area_alloc.
Signed-off-by: Sebastian Ott <sebott@linux.vnet.ibm.com>
Reviewed-by: Gerald Schaefer <gerald.schaefer@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/pci/pci_dma.c

@@ -226,7 +226,8 @@ static unsigned long __dma_alloc_iommu(struct device *dev,
 	boundary_size = ALIGN(dma_get_seg_boundary(dev) + 1,
 			      PAGE_SIZE) >> PAGE_SHIFT;
 	return iommu_area_alloc(zdev->iommu_bitmap, zdev->iommu_pages,
-				start, size, 0, boundary_size, 0);
+				start, size, zdev->start_dma >> PAGE_SHIFT,
+				boundary_size, 0);
 }
 
 static unsigned long dma_alloc_iommu(struct device *dev, int size)