xen/arm: initialize grant_table on ARM

Initialize the grant table mapping at the address specified at index 0
in the DT under the /xen node.
After the grant table is initialized, call xenbus_probe (if not dom0).

Changes in v2:

- introduce GRANT_TABLE_PHYSADDR;
- remove unneeded initialization of boot_max_nr_grant_frames.
Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>

arch/arm/xen/enlighten.c

 #include <xen/xen.h>
+#include <xen/grant_table.h>
+#include <xen/hvm.h>
 #include <xen/interface/xen.h>
 #include <xen/interface/memory.h>
+#include <xen/interface/hvm/params.h>
 #include <xen/features.h>
 #include <xen/platform_pci.h>
+#include <xen/xenbus.h>
 #include <asm/xen/hypervisor.h>
 #include <asm/xen/hypercall.h>
 #include <linux/module.h>
@@ -42,6 +46,7 @@ EXPORT_SYMBOL_GPL(xen_remap_domain_mfn_range);
  * see Documentation/devicetree/bindings/arm/xen.txt for the
  * documentation of the Xen Device Tree format.
  */
+#define GRANT_TABLE_PHYSADDR 0
 static int __init xen_guest_init(void)
 {
 	struct xen_add_to_physmap xatp;
@@ -51,6 +56,7 @@ static int __init xen_guest_init(void)
 	const char *s = NULL;
 	const char *version = NULL;
 	const char *xen_prefix = "xen,xen-";
+	struct resource res;
 
 	node = of_find_compatible_node(NULL, NULL, "xen,xen");
 	if (!node) {
@@ -65,6 +71,9 @@ static int __init xen_guest_init(void)
 		pr_debug("Xen version not found\n");
 		return 0;
 	}
+	if (of_address_to_resource(node, GRANT_TABLE_PHYSADDR, &res))
+		return 0;
+	xen_hvm_resume_frames = res.start >> PAGE_SHIFT;
 	xen_domain_type = XEN_HVM_DOMAIN;
 
 	xen_setup_features();
@@ -98,6 +107,11 @@ static int __init xen_guest_init(void)
 	 * is required to use VCPUOP_register_vcpu_info to place vcpu info
 	 * for secondary CPUs as they are brought up. */
 	per_cpu(xen_vcpu, 0) = &HYPERVISOR_shared_info->vcpu_info[0];
+
+	gnttab_init();
+	if (!xen_initial_domain())
+		xenbus_probe(NULL);
+
 	return 0;
 }
 core_initcall(xen_guest_init);