References: bnc#470949

--- a/xen/arch/x86/mm/shadow/common.c
+++ b/xen/arch/x86/mm/shadow/common.c
@@ -1902,7 +1902,7 @@ static void sh_hash_audit_bucket(struct 
                 {
                     if ( !page_is_out_of_sync(gpg) )
                     {
-                        SHADOW_ERROR("MFN %#lx shadowed (by %#"PRI_mfn")"
+                        SHADOW_ERROR("MFN %#x shadowed (by %#"PRI_mfn")"
                                      " and not OOS but has typecount %#lx\n",
                                      sp->backpointer, 
                                      mfn_x(shadow_page_to_mfn(sp)), 
@@ -1916,7 +1916,7 @@ static void sh_hash_audit_bucket(struct 
             if ( (gpg->u.inuse.type_info & PGT_type_mask) == PGT_writable_page 
                  && (gpg->u.inuse.type_info & PGT_count_mask) != 0 )
             {
-                SHADOW_ERROR("MFN %#lx shadowed (by %#"PRI_mfn")"
+                SHADOW_ERROR("MFN %#x shadowed (by %#"PRI_mfn")"
                              " but has typecount %#lx\n",
                              sp->backpointer, mfn_x(shadow_page_to_mfn(sp)), 
                              gpg->u.inuse.type_info);
--- a/xen/arch/x86/mm/shadow/private.h
+++ b/xen/arch/x86/mm/shadow/private.h
@@ -190,7 +190,7 @@ struct shadow_page_info
         struct {
             union {
                 /* When in use, guest page we're a shadow of */
-                unsigned long backpointer;
+                unsigned int backpointer;
                 /* When free, order of the freelist we're on */
                 unsigned int order;
             };
@@ -204,12 +204,17 @@ struct shadow_page_info
                 /* When free, TLB flush time when freed */
                 u32 tlbflush_timestamp;
             };
+#ifdef __i386__
+            unsigned long mbz;     /* Must be zero: count_info is here. */
+#endif
             struct {
-                unsigned long mbz;     /* Must be zero: count_info is here. */
                 unsigned long type:5;   /* What kind of shadow is this? */
                 unsigned long pinned:1; /* Is the shadow pinned? */
                 unsigned long count:26; /* Reference count */
             };
+#ifndef __i386__
+            unsigned long mbz;     /* Must be zero: count_info is here. */
+#endif
             union {
                 /* For unused shadow pages, a list of pages of this order; for 
                  * pinnable shadows, if pinned, a list of other pinned shadows
@@ -645,7 +650,7 @@ static inline int sh_get_ref(struct vcpu
 
     if ( unlikely(nx >= 1U<<26) )
     {
-        SHADOW_PRINTK("shadow ref overflow, gmfn=%" PRtype_info " smfn=%lx\n",
+        SHADOW_PRINTK("shadow ref overflow, gmfn=%x smfn=%lx\n",
                        sp->backpointer, mfn_x(smfn));
         return 0;
     }
--- a/xen/include/asm-x86/mm.h
+++ b/xen/include/asm-x86/mm.h
@@ -15,7 +15,7 @@
  *  1. 'struct page_info' contains a 'struct list_head list'.
  *  2. Provide a PFN_ORDER() macro for accessing the order of a free page.
  */
-#define PFN_ORDER(_pfn) ((_pfn)->u.free.order)
+#define PFN_ORDER(_pfn) ((_pfn)->v.free.order)
 
 struct page_info
 {
@@ -30,16 +30,12 @@ struct page_info
 
         /* Page is in use: ((count_info & PGC_count_mask) != 0). */
         struct {
-            /* Owner of this page (NULL if page is anonymous). */
-            u32 _domain; /* pickled format */
             /* Type reference count and various PGT_xxx flags and fields. */
             unsigned long type_info;
         } inuse;
 
         /* Page is on a free list: ((count_info & PGC_count_mask) == 0). */
         struct {
-            /* Order-size of the free chunk this page is the head of. */
-            u32 order;
             /* Mask of possibly-tainted TLBs. */
             cpumask_t cpumask;
         } free;
@@ -47,6 +43,22 @@ struct page_info
     } u;
 
     union {
+
+        /* Page is in use. */
+        struct {
+            /* Owner of this page (NULL if page is anonymous). */
+            u32 _domain; /* pickled format */
+        } inuse;
+
+        /* Page is on a free list. */
+        struct {
+            /* Order-size of the free chunk this page is the head of. */
+            u32 order;
+        } free;
+
+    } v;
+
+    union {
         /*
          * Timestamp from 'TLB clock', used to avoid extra safety flushes.
          * Only valid for: a) free pages, and b) pages with zero type count
@@ -173,8 +185,8 @@ static inline u32 pickle_domptr(struct d
 /* OOS fixup entries */
 #define SHADOW_OOS_FIXUPS 2
 
-#define page_get_owner(_p)    (unpickle_domptr((_p)->u.inuse._domain))
-#define page_set_owner(_p,_d) ((_p)->u.inuse._domain = pickle_domptr(_d))
+#define page_get_owner(_p)    (unpickle_domptr((_p)->v.inuse._domain))
+#define page_set_owner(_p,_d) ((_p)->v.inuse._domain = pickle_domptr(_d))
 
 #define maddr_get_owner(ma)   (page_get_owner(maddr_to_page((ma))))
 #define vaddr_get_owner(va)   (page_get_owner(virt_to_page((va))))