x86, xen: short-circuit tests for dom0

When testing for a dom0/initial/privileged domain, make sure the
predicate evaluates to a compile-time 0 if CONFIG_XEN_DOM0 isn't
enabled.  This will make most of the dom0 code evaporate without
much more effort.
Signed-off-by: NJeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

arch/x86/include/asm/xen/hypervisor.h

@@ -38,22 +38,30 @@ extern struct shared_info *HYPERVISOR_shared_info;
 extern struct start_info *xen_start_info;
 
 enum xen_domain_type {
-	XEN_NATIVE,
-	XEN_PV_DOMAIN,
-	XEN_HVM_DOMAIN,
+	XEN_NATIVE,		/* running on bare hardware    */
+	XEN_PV_DOMAIN,		/* running in a PV domain      */
+	XEN_HVM_DOMAIN,		/* running in a Xen hvm domain */
 };
 
-extern enum xen_domain_type xen_domain_type;
-
 #ifdef CONFIG_XEN
-#define xen_domain()		(xen_domain_type != XEN_NATIVE)
+extern enum xen_domain_type xen_domain_type;
 #else
-#define xen_domain()		(0)
+#define xen_domain_type		XEN_NATIVE
 #endif
 
-#define xen_pv_domain()		(xen_domain() && xen_domain_type == XEN_PV_DOMAIN)
-#define xen_hvm_domain()	(xen_domain() && xen_domain_type == XEN_HVM_DOMAIN)
+#define xen_domain()		(xen_domain_type != XEN_NATIVE)
+#define xen_pv_domain()		(xen_domain() &&			\
+				 xen_domain_type == XEN_PV_DOMAIN)
+#define xen_hvm_domain()	(xen_domain() &&			\
+				 xen_domain_type == XEN_HVM_DOMAIN)
+
+#ifdef CONFIG_XEN_DOM0
+#include <xen/interface/xen.h>
 
-#define xen_initial_domain()	(xen_pv_domain() && xen_start_info->flags & SIF_INITDOMAIN)
+#define xen_initial_domain()	(xen_pv_domain() && \
+				 xen_start_info->flags & SIF_INITDOMAIN)
+#else  /* !CONFIG_XEN_DOM0 */
+#define xen_initial_domain()	(0)
+#endif	/* CONFIG_XEN_DOM0 */
 
 #endif /* _ASM_X86_XEN_HYPERVISOR_H */