arch/x86/xen: Silence compiler warnings

Compiler complains in the following way when x86 32-bit kernel
with Xen support is build:

  CC      arch/x86/xen/enlighten.o
arch/x86/xen/enlighten.c: In function ‘xen_start_kernel’:
arch/x86/xen/enlighten.c:1726:3: warning: right shift count >= width of type [enabled by default]

Such line contains following EFI initialization code:

boot_params.efi_info.efi_systab_hi = (__u32)(__pa(efi_systab_xen) >> 32);

There is no issue if x86 64-bit kernel is build. However, 32-bit case
generate warning (even if that code will not be executed because Xen
does not work on 32-bit EFI platforms) due to __pa() returning unsigned long
type which has 32-bits width. So move whole EFI initialization stuff
to separate function and build it conditionally to avoid above mentioned
warning on x86 32-bit architecture.

Signed-off-by: Daniel Kiper <daniel.kiper@oracle.com>
Reviewed-by: Konrad Rzeszutek Wilk <Konrad.wilk@oracle.com>
Signed-off-by: Matt Fleming <matt.fleming@intel.com>

arch/x86/xen/Makefile

@@ -22,3 +22,4 @@ obj-$(CONFIG_PARAVIRT_SPINLOCKS)+= spinlock.o
 obj-$(CONFIG_XEN_DEBUG_FS)	+= debugfs.o
 obj-$(CONFIG_XEN_DOM0)		+= apic.o vga.o
 obj-$(CONFIG_SWIOTLB_XEN)	+= pci-swiotlb-xen.o
+obj-$(CONFIG_XEN_EFI)		+= efi.o

arch/x86/xen/efi.c

@@ -0,0 +1,43 @@
+/*
+ * Copyright (c) 2014 Oracle Co., Daniel Kiper
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <linux/efi.h>
+#include <linux/init.h>
+#include <linux/string.h>
+
+#include <xen/xen-ops.h>
+
+#include <asm/setup.h>
+
+void __init xen_efi_init(void)
+{
+	efi_system_table_t *efi_systab_xen;
+
+	efi_systab_xen = xen_efi_probe();
+
+	if (efi_systab_xen == NULL)
+		return;
+
+	strncpy((char *)&boot_params.efi_info.efi_loader_signature, "Xen",
+			sizeof(boot_params.efi_info.efi_loader_signature));
+	boot_params.efi_info.efi_systab = (__u32)__pa(efi_systab_xen);
+	boot_params.efi_info.efi_systab_hi = (__u32)(__pa(efi_systab_xen) >> 32);
+
+	set_bit(EFI_BOOT, &efi.flags);
+	set_bit(EFI_PARAVIRT, &efi.flags);
+	set_bit(EFI_64BIT, &efi.flags);
+}

arch/x86/xen/enlighten.c

@@ -32,7 +32,6 @@
 #include <linux/gfp.h>
 #include <linux/memblock.h>
 #include <linux/edd.h>
-#include <linux/efi.h>
 
 #include <xen/xen.h>
 #include <xen/events.h>
@@ -1521,7 +1520,6 @@ asmlinkage __visible void __init xen_start_kernel(void)
 {
 	struct physdev_set_iopl set_iopl;
 	int rc;
-	efi_system_table_t *efi_systab_xen;
 
 	if (!xen_start_info)
 		return;
@@ -1717,18 +1715,7 @@ asmlinkage __visible void __init xen_start_kernel(void)
 
 	xen_setup_runstate_info(0);
 
-	efi_systab_xen = xen_efi_probe();
+	xen_efi_init();
-
-	if (efi_systab_xen) {
-		strncpy((char *)&boot_params.efi_info.efi_loader_signature, "Xen",
-				sizeof(boot_params.efi_info.efi_loader_signature));
-		boot_params.efi_info.efi_systab = (__u32)__pa(efi_systab_xen);
-		boot_params.efi_info.efi_systab_hi = (__u32)(__pa(efi_systab_xen) >> 32);
-
-		set_bit(EFI_BOOT, &efi.flags);
-		set_bit(EFI_PARAVIRT, &efi.flags);
-		set_bit(EFI_64BIT, &efi.flags);
-	}
 
 	/* Start the world */
 #ifdef CONFIG_X86_32

arch/x86/xen/xen-ops.h

@@ -104,6 +104,14 @@ static inline void __init xen_init_apic(void)
 }
 #endif
 
+#ifdef CONFIG_XEN_EFI
+extern void xen_efi_init(void);
+#else
+static inline void __init xen_efi_init(void)
+{
+}
+#endif
+
 /* Declare an asm function, along with symbols needed to make it
    inlineable */
 #define DECL_ASM(ret, name, ...)		\