On Wed, Jan 23, 2019 at 05:30:46PM +0100, Joerg Roedel wrote:

+bool is_swiotlb_active(void)
+{
+	return !no_iotlb_memory;
+}

As I've just introduced and fixed a bug in this area in the current
cycle - I don't think no_iotlb_memory is what your want (and maybe
not useful at all): if the arch valls swiotlb_exit after previously
initializing a buffer it won't be set.  You probably want to check
for non-zero io_tlb_start and/or io_tlb_end.