Index: qemu/hw/dma/i8257.c
@@ -344,9 +344,11 @@ static void channel_run (int ncont, int 
     }
 #endif
 
-    n = r->transfer_handler (r->opaque, ichan + (ncont << 2),
-                             r->now[COUNT], (r->base[COUNT] + 1) << ncont);
-    r->now[COUNT] = n;
+    if (r->transfer_handler) {
+        n = r->transfer_handler (r->opaque, ichan + (ncont << 2),
+                                 r->now[COUNT], (r->base[COUNT] + 1) << ncont);
+        r->now[COUNT] = n;
+    }
     ldebug ("dma_pos %d size %d\n", n, (r->base[COUNT] + 1) << ncont);
 }
 
Index: qemu-0.8.2/hw/audio/sb16.c
@@ -1235,8 +1235,10 @@ static int SB_read_DMA (void *opaque, in
             s->block_size);
 #endif
 
-    while (s->left_till_irq <= 0) {
-        s->left_till_irq = s->block_size + s->left_till_irq;
+    if (s->block_size) {
+        while (s->left_till_irq <= 0) {
+            s->left_till_irq = s->block_size + s->left_till_irq;
+        }
     }
 
     return dma_pos;