Re: [PATCH v3 5/9] xen/gntdev: Allow mappings for DMA buffers

From: Oleksandr Andrushchenko
Date: Thu Jun 14 2018 - 03:00:37 EST

@@ -548,6 +632,17 @@ static int gntdev_open(struct inode *inode, struct file *flip)
flip->private_data = priv;
+ priv->dma_dev = gntdev_miscdev.this_device;
+ /*
+ * The device is not spawn from a device tree, so arch_setup_dma_ops
+ * is not called, thus leaving the device with dummy DMA ops.
+ * Fix this call of_dma_configure() with a NULL node to set
+ * default DMA ops.
+ */
+ of_dma_configure(priv->dma_dev, NULL);
Please note, that the code above will need a change while
applying to the mainline kernel because of API changes [1].
Unfortunately, current Xen tip kernel tree is v4.17-rc5 based,
so I cannot make the change in this patch now.

The change is trivial and requires:
-of_dma_configure(priv->dma_dev, NULL);
+of_dma_configure(priv->dma_dev, NULL, true);
pr_debug("priv %p\n", priv);
return 0;