xen-gntalloc: Userspace grant allocation driver

This allows a userspace application to allocate a shared page for
implementing inter-domain communication or device drivers. These
shared pages can be mapped using the gntdev device or by the kernel
in another domain.

Signed-off-by: Daniel De Graaf <dgdegra@tycho.nsa.gov>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
diff --git a/drivers/xen/Kconfig b/drivers/xen/Kconfig
index 07bec09..a3d7afb 100644
--- a/drivers/xen/Kconfig
+++ b/drivers/xen/Kconfig
@@ -80,6 +80,14 @@
 	help
 	  Allows userspace processes to use grants.
 
+config XEN_GRANT_DEV_ALLOC
+	tristate "User-space grant reference allocator driver"
+	depends on XEN
+	help
+	  Allows userspace processes to create pages with access granted
+	  to other domains. This can be used to implement frontend drivers
+	  or as part of an inter-domain shared memory channel.
+
 config XEN_PLATFORM_PCI
 	tristate "xen platform pci device driver"
 	depends on XEN_PVHVM && PCI