diff -Naur linux-4.16.2/lib/swiotlb.c linux-4.16.2-p/lib/swiotlb.c
--- linux-4.16.2/lib/swiotlb.c	2018-04-12 12:30:01.000000000 +0200
+++ linux-4.16.2-p/lib/swiotlb.c	2018-04-12 18:01:27.122073379 +0200
@@ -732,7 +732,7 @@
 		goto out_warn;
 
 	*dma_handle = swiotlb_phys_to_dma(dev, phys_addr);
-	if (dma_coherent_ok(dev, *dma_handle, size))
+	if (!dma_coherent_ok(dev, *dma_handle, size))
 		goto out_unmap;
 
 	memset(phys_to_virt(phys_addr), 0, size);