arm/xen: Assign xen-grant DMA ops for xen-grant DMA devices

By assigning xen-grant DMA ops we will restrict memory access for
passed device using Xen grant mappings. This is needed for using any
virtualized device (e.g. virtio) in Xen guests in a safe manner.

Please note, for the virtio devices the XEN_VIRTIO config should
be enabled (it forces ARCH_HAS_RESTRICTED_VIRTIO_MEMORY_ACCESS).

Signed-off-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
Link: https://lore.kernel.org/r/1654197833-25362-9-git-send-email-olekstysh@gmail.com
Signed-off-by: Juergen Gross <jgross@suse.com>

Author: Oleksandr Tyshchenko

include/xen/arm/xen-ops.h

@@ -3,11 +3,14 @@
 #define _ASM_ARM_XEN_OPS_H
 
 #include <xen/swiotlb-xen.h>
+#include <xen/xen-ops.h>
 
 static inline void xen_setup_dma_ops(struct device *dev)
 {
 #ifdef CONFIG_XEN
-	if (xen_swiotlb_detect())
+	if (xen_is_grant_dma_device(dev))
+		xen_grant_setup_dma_ops(dev);
+	else if (xen_swiotlb_detect())
 		dev->dma_ops = &xen_swiotlb_dma_ops;
 #endif
 }