x86/efi: Implement a __efi_call_virt macro

For i386, all the EFI system runtime services functions return efi_status_t
except efi_reset_system_system. Therefore, not all functions can be covered
by the same macro in case the macro needs to do more than calling the function
(i.e., return a value). The purpose of the __efi_call_virt macro is to be used
when no return value is expected.

For x86_64, this macro would not be needed as all the runtime services return
u64. However, the same code is used for both x86_64 and i386. Thus, the macro
__efi_call_virt is also defined to not break compilation.
Signed-off-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
Cc: Borislav Petkov <bp@suse.de>
Signed-off-by: Matt Fleming <matt.fleming@intel.com>

arch/x86/include/asm/efi.h

@@ -31,9 +31,13 @@ extern unsigned long asmlinkage efi_call_phys(void *, ...);
  * Wrap all the virtual calls in a way that forces the parameters on the stack.
  */
 
+/* Use this macro if your virtual returns a non-void value */
 #define efi_call_virt(f, args...) \
 	((efi_##f##_t __attribute__((regparm(0)))*)efi.systab->runtime->f)(args)
 
+/* Use this macro if your virtual call does not return any value */
+#define __efi_call_virt(f, args...) efi_call_virt(f, args)
+
 #define efi_ioremap(addr, size, type, attr)	ioremap_cache(addr, size)
 
 #else /* !CONFIG_X86_32 */
@@ -55,6 +59,12 @@ extern u64 asmlinkage efi_call(void *fp, ...);
 	__s;								\
 })
 
+/*
+ * All X86_64 virt calls return non-void values. Thus, use non-void call for
+ * virt calls that would be void on X86_32.
+ */
+#define __efi_call_virt(f, args...) efi_call_virt(f, args)
+
 extern void __iomem *efi_ioremap(unsigned long addr, unsigned long size,
 				 u32 type, u64 attribute);
 

arch/x86/platform/efi/efi.c

@@ -202,8 +202,8 @@ static void virt_efi_reset_system(int reset_type,
 				  unsigned long data_size,
 				  efi_char16_t *data)
 {
-	efi_call_virt(reset_system, reset_type, status,
-		      data_size, data);
+	__efi_call_virt(reset_system, reset_type, status,
+			data_size, data);
 }
 
 static efi_status_t virt_efi_update_capsule(efi_capsule_header_t **capsules,