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

[Oleksandr Andrushchenko]

@@ -548,6 +632,17 @@ static int gntdev_open(struct inode *inode, struct 
file *flip)
>   	}
>   
>   	flip->private_data = priv;
> +#ifdef CONFIG_XEN_GRANT_DMA_ALLOC
> +	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);
> +#endif
>   	pr_debug("priv %p\n", priv);
>   
>   	return 0;
[1] 
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=3d6ce86ee79465e1b1b6e287f8ea26b553fc768e