Index: /trunk/src/VBox/VMM/PGMPhys.cpp
===================================================================
--- /trunk/src/VBox/VMM/PGMPhys.cpp	(revision 29318)
+++ /trunk/src/VBox/VMM/PGMPhys.cpp	(revision 29319)
@@ -767,4 +767,5 @@
 }
 
+#if HC_ARCH_BITS == 64 && (defined(RT_OS_WINDOWS) || defined(RT_OS_SOLARIS) || defined(RT_OS_LINUX) || defined(RT_OS_FREEBSD))
 /**
  * Rendezvous callback used by PGMR3ChangeMemBalloon that changes the memory balloon size
@@ -908,4 +909,5 @@
     RTMemFree(paPhysPage);
 }
+#endif
 
 /**
@@ -920,4 +922,6 @@
 VMMR3DECL(int) PGMR3PhysChangeMemBalloon(PVM pVM, bool fInflate, unsigned cPages, RTGCPHYS *paPhysPage)
 {
+    /* This must match GMMR0Init; currently we only support memory ballooning on all 64-bit hosts except Mac OS X */
+#if HC_ARCH_BITS == 64 && (defined(RT_OS_WINDOWS) || defined(RT_OS_SOLARIS) || defined(RT_OS_LINUX) || defined(RT_OS_FREEBSD))
     int rc;
 
@@ -950,4 +954,7 @@
     }
     return rc;
+#else
+    return VERR_NOT_IMPLEMENTED;
+#endif
 }