diff --git a/xen/arch/arm/p2m.c b/xen/arch/arm/p2m.c
index 34563bb..d690602 100644
--- a/xen/arch/arm/p2m.c
+++ b/xen/arch/arm/p2m.c
@@ -1461,7 +1461,7 @@ int relinquish_p2m_mapping(struct domain *d)
     return apply_p2m_changes(d, RELINQUISH,
                               pfn_to_paddr(p2m->lowest_mapped_gfn),
                               pfn_to_paddr(p2m->max_mapped_gfn),
-                              pfn_to_paddr(INVALID_MFN),
+                              pfn_to_paddr(mfn_x(INVALID_MFN)),
                               MATTR_MEM, 0, p2m_invalid,
                               d->arch.p2m.default_access);
 }
@@ -1476,7 +1476,7 @@ int p2m_cache_flush(struct domain *d, xen_pfn_t start_mfn, xen_pfn_t end_mfn)
     return apply_p2m_changes(d, CACHEFLUSH,
                              pfn_to_paddr(start_mfn),
                              pfn_to_paddr(end_mfn),
-                             pfn_to_paddr(INVALID_MFN),
+                             pfn_to_paddr(mfn_x(INVALID_MFN)),
                              MATTR_MEM, 0, p2m_invalid,
                              d->arch.p2m.default_access);
 }
diff --git a/xen/arch/x86/cpu/mcheck/mce.c b/xen/arch/x86/cpu/mcheck/mce.c
index edcbe48..2695b0c 100644
--- a/xen/arch/x86/cpu/mcheck/mce.c
+++ b/xen/arch/x86/cpu/mcheck/mce.c
@@ -1455,7 +1455,7 @@ long do_mca(XEN_GUEST_HANDLE_PARAM(xen_mc_t) u_xen_mc)
                 gfn = PFN_DOWN(gaddr);
                 mfn = mfn_x(get_gfn(d, gfn, &t));
 
-                if ( mfn == INVALID_MFN )
+                if ( mfn == mfn_x(INVALID_MFN) )
                 {
                     put_gfn(d, gfn);
                     put_domain(d);
diff --git a/xen/arch/x86/debug.c b/xen/arch/x86/debug.c
index 58cae22..9213ea7 100644
--- a/xen/arch/x86/debug.c
+++ b/xen/arch/x86/debug.c
@@ -43,11 +43,11 @@ typedef unsigned long dbgva_t;
 typedef unsigned char dbgbyte_t;
 
 /* Returns: mfn for the given (hvm guest) vaddr */
-static unsigned long 
+static mfn_t
 dbg_hvm_va2mfn(dbgva_t vaddr, struct domain *dp, int toaddr,
                 unsigned long *gfn)
 {
-    unsigned long mfn;
+    mfn_t mfn;
     uint32_t pfec = PFEC_page_present;
     p2m_type_t gfntype;
 
@@ -60,16 +60,17 @@ dbg_hvm_va2mfn(dbgva_t vaddr, struct domain *dp, int toaddr,
         return INVALID_MFN;
     }
 
-    mfn = mfn_x(get_gfn(dp, *gfn, &gfntype)); 
+    mfn = get_gfn(dp, *gfn, &gfntype);
     if ( p2m_is_readonly(gfntype) && toaddr )
     {
         DBGP2("kdb:p2m_is_readonly: gfntype:%x\n", gfntype);
         mfn = INVALID_MFN;
     }
     else
-        DBGP2("X: vaddr:%lx domid:%d mfn:%lx\n", vaddr, dp->domain_id, mfn);
+        DBGP2("X: vaddr:%lx domid:%d mfn:%#"PRI_mfn"\n",
+              vaddr, dp->domain_id, mfn_x(mfn));
 
-    if ( mfn == INVALID_MFN )
+    if ( mfn_eq(mfn, INVALID_MFN) )
     {
         put_gfn(dp, *gfn);
         *gfn = INVALID_GFN;
@@ -91,7 +92,7 @@ dbg_hvm_va2mfn(dbgva_t vaddr, struct domain *dp, int toaddr,
  *       mode.
  * Returns: mfn for the given (pv guest) vaddr 
  */
-static unsigned long 
+static mfn_t
 dbg_pv_va2mfn(dbgva_t vaddr, struct domain *dp, uint64_t pgd3val)
 {
     l4_pgentry_t l4e, *l4t;
@@ -99,31 +100,31 @@ dbg_pv_va2mfn(dbgva_t vaddr, struct domain *dp, uint64_t pgd3val)
     l2_pgentry_t l2e, *l2t;
     l1_pgentry_t l1e, *l1t;
     unsigned long cr3 = (pgd3val ? pgd3val : dp->vcpu[0]->arch.cr3);
-    unsigned long mfn = cr3 >> PAGE_SHIFT;
+    mfn_t mfn = _mfn(cr3 >> PAGE_SHIFT);
 
     DBGP2("vaddr:%lx domid:%d cr3:%lx pgd3:%lx\n", vaddr, dp->domain_id, 
           cr3, pgd3val);
 
     if ( pgd3val == 0 )
     {
-        l4t = map_domain_page(_mfn(mfn));
+        l4t = map_domain_page(mfn);
         l4e = l4t[l4_table_offset(vaddr)];
         unmap_domain_page(l4t);
-        mfn = l4e_get_pfn(l4e);
-        DBGP2("l4t:%p l4to:%lx l4e:%lx mfn:%lx\n", l4t, 
-              l4_table_offset(vaddr), l4e, mfn);
+        mfn = _mfn(l4e_get_pfn(l4e));
+        DBGP2("l4t:%p l4to:%lx l4e:%lx mfn:%#"PRI_mfn"\n", l4t,
+              l4_table_offset(vaddr), l4e, mfn_x(mfn));
         if ( !(l4e_get_flags(l4e) & _PAGE_PRESENT) )
         {
             DBGP1("l4 PAGE not present. vaddr:%lx cr3:%lx\n", vaddr, cr3);
             return INVALID_MFN;
         }
 
-        l3t = map_domain_page(_mfn(mfn));
+        l3t = map_domain_page(mfn);
         l3e = l3t[l3_table_offset(vaddr)];
         unmap_domain_page(l3t);
-        mfn = l3e_get_pfn(l3e);
-        DBGP2("l3t:%p l3to:%lx l3e:%lx mfn:%lx\n", l3t, 
-              l3_table_offset(vaddr), l3e, mfn);
+        mfn = _mfn(l3e_get_pfn(l3e));
+        DBGP2("l3t:%p l3to:%lx l3e:%lx mfn:%#"PRI_mfn"\n", l3t,
+              l3_table_offset(vaddr), l3e, mfn_x(mfn));
         if ( !(l3e_get_flags(l3e) & _PAGE_PRESENT) ||
              (l3e_get_flags(l3e) & _PAGE_PSE) )
         {
@@ -132,26 +133,26 @@ dbg_pv_va2mfn(dbgva_t vaddr, struct domain *dp, uint64_t pgd3val)
         }
     }
 
-    l2t = map_domain_page(_mfn(mfn));
+    l2t = map_domain_page(mfn);
     l2e = l2t[l2_table_offset(vaddr)];
     unmap_domain_page(l2t);
-    mfn = l2e_get_pfn(l2e);
-    DBGP2("l2t:%p l2to:%lx l2e:%lx mfn:%lx\n", l2t, l2_table_offset(vaddr),
-          l2e, mfn);
+    mfn = _mfn(l2e_get_pfn(l2e));
+    DBGP2("l2t:%p l2to:%lx l2e:%lx mfn:%#"PRI_mfn"\n",
+          l2t, l2_table_offset(vaddr), l2e, mfn_x(mfn));
     if ( !(l2e_get_flags(l2e) & _PAGE_PRESENT) ||
          (l2e_get_flags(l2e) & _PAGE_PSE) )
     {
         DBGP1("l2 PAGE not present. vaddr:%lx cr3:%lx\n", vaddr, cr3);
         return INVALID_MFN;
     }
-    l1t = map_domain_page(_mfn(mfn));
+    l1t = map_domain_page(mfn);
     l1e = l1t[l1_table_offset(vaddr)];
     unmap_domain_page(l1t);
-    mfn = l1e_get_pfn(l1e);
-    DBGP2("l1t:%p l1to:%lx l1e:%lx mfn:%lx\n", l1t, l1_table_offset(vaddr),
-          l1e, mfn);
+    mfn = _mfn(l1e_get_pfn(l1e));
+    DBGP2("l1t:%p l1to:%lx l1e:%lx mfn:%#"PRI_mfn"\n", l1t, l1_table_offset(vaddr),
+          l1e, mfn_x(mfn));
 
-    return mfn_valid(mfn) ? mfn : INVALID_MFN;
+    return mfn_valid(mfn_x(mfn)) ? mfn : INVALID_MFN;
 }
 
 /* Returns: number of bytes remaining to be copied */
@@ -163,23 +164,24 @@ unsigned int dbg_rw_guest_mem(struct domain *dp, void * __user gaddr,
     {
         char *va;
         unsigned long addr = (unsigned long)gaddr;
-        unsigned long mfn, gfn = INVALID_GFN, pagecnt;
+        mfn_t mfn;
+        unsigned long gfn = INVALID_GFN, pagecnt;
 
         pagecnt = min_t(long, PAGE_SIZE - (addr & ~PAGE_MASK), len);
 
         mfn = (has_hvm_container_domain(dp)
                ? dbg_hvm_va2mfn(addr, dp, toaddr, &gfn)
                : dbg_pv_va2mfn(addr, dp, pgd3));
-        if ( mfn == INVALID_MFN ) 
+        if ( mfn_eq(mfn, INVALID_MFN) )
             break;
 
-        va = map_domain_page(_mfn(mfn));
+        va = map_domain_page(mfn);
         va = va + (addr & (PAGE_SIZE-1));
 
         if ( toaddr )
         {
             copy_from_user(va, buf, pagecnt);    /* va = buf */
-            paging_mark_dirty(dp, mfn);
+            paging_mark_dirty(dp, mfn_x(mfn));
         }
         else
         {
diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
index c89ab6e..f3faf2e 100644
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -1796,7 +1796,7 @@ int hvm_hap_nested_page_fault(paddr_t gpa, unsigned long gla,
         p2m = hostp2m;
 
     /* Check access permissions first, then handle faults */
-    if ( mfn_x(mfn) != INVALID_MFN )
+    if ( !mfn_eq(mfn, INVALID_MFN) )
     {
         bool_t violation;
 
@@ -5299,8 +5299,8 @@ static int do_altp2m_op(
             rc = -EINVAL;
 
         if ( (gfn_x(vcpu_altp2m(curr).veinfo_gfn) != INVALID_GFN) ||
-             (mfn_x(get_gfn_query_unlocked(curr->domain,
-                    a.u.enable_notify.gfn, &p2mt)) == INVALID_MFN) )
+             mfn_eq(get_gfn_query_unlocked(curr->domain,
+                    a.u.enable_notify.gfn, &p2mt), INVALID_MFN) )
             return -EINVAL;
 
         vcpu_altp2m(curr).veinfo_gfn = _gfn(a.u.enable_notify.gfn);
diff --git a/xen/arch/x86/hvm/viridian.c b/xen/arch/x86/hvm/viridian.c
index 8253fd0..1734b7e 100644
--- a/xen/arch/x86/hvm/viridian.c
+++ b/xen/arch/x86/hvm/viridian.c
@@ -195,8 +195,8 @@ static void enable_hypercall_page(struct domain *d)
     {
         if ( page )
             put_page(page);
-        gdprintk(XENLOG_WARNING, "Bad GMFN %lx (MFN %lx)\n", gmfn,
-                 page ? page_to_mfn(page) : INVALID_MFN);
+        gdprintk(XENLOG_WARNING, "Bad GMFN %#"PRI_gfn" (MFN %#"PRI_mfn")\n",
+                 gmfn, page ? page_to_mfn(page) : mfn_x(INVALID_MFN));
         return;
     }
 
@@ -268,8 +268,8 @@ static void initialize_apic_assist(struct vcpu *v)
     return;
 
  fail:
-    gdprintk(XENLOG_WARNING, "Bad GMFN %lx (MFN %lx)\n", gmfn,
-             page ? page_to_mfn(page) : INVALID_MFN);
+    gdprintk(XENLOG_WARNING, "Bad GMFN %#"PRI_gfn" (MFN %#"PRI_mfn")\n", gmfn,
+             page ? page_to_mfn(page) : mfn_x(INVALID_MFN));
 }
 
 static void teardown_apic_assist(struct vcpu *v)
@@ -348,8 +348,8 @@ static void update_reference_tsc(struct domain *d, bool_t initialize)
     {
         if ( page )
             put_page(page);
-        gdprintk(XENLOG_WARNING, "Bad GMFN %lx (MFN %lx)\n", gmfn,
-                 page ? page_to_mfn(page) : INVALID_MFN);
+        gdprintk(XENLOG_WARNING, "Bad GMFN %#"PRI_gfn" (MFN %#"PRI_mfn")\n",
+                 gmfn, page ? page_to_mfn(page) : mfn_x(INVALID_MFN));
         return;
     }
 
diff --git a/xen/arch/x86/hvm/vmx/vmx.c b/xen/arch/x86/hvm/vmx/vmx.c
index df19579..a061420 100644
--- a/xen/arch/x86/hvm/vmx/vmx.c
+++ b/xen/arch/x86/hvm/vmx/vmx.c
@@ -2025,7 +2025,7 @@ static void vmx_vcpu_update_vmfunc_ve(struct vcpu *v)
 
             mfn = get_gfn_query_unlocked(d, gfn_x(vcpu_altp2m(v).veinfo_gfn), &t);
 
-            if ( mfn_x(mfn) != INVALID_MFN )
+            if ( !mfn_eq(mfn, INVALID_MFN) )
                 __vmwrite(VIRT_EXCEPTION_INFO, mfn_x(mfn) << PAGE_SHIFT);
             else
                 v->arch.hvm_vmx.secondary_exec_control &=
diff --git a/xen/arch/x86/mm/guest_walk.c b/xen/arch/x86/mm/guest_walk.c
index e850502..868e909 100644
--- a/xen/arch/x86/mm/guest_walk.c
+++ b/xen/arch/x86/mm/guest_walk.c
@@ -281,7 +281,7 @@ guest_walk_tables(struct vcpu *v, struct p2m_domain *p2m,
         start = _gfn((gfn_x(start) & ~GUEST_L3_GFN_MASK) +
                      ((va >> PAGE_SHIFT) & GUEST_L3_GFN_MASK));
         gw->l1e = guest_l1e_from_gfn(start, flags);
-        gw->l2mfn = gw->l1mfn = _mfn(INVALID_MFN);
+        gw->l2mfn = gw->l1mfn = INVALID_MFN;
         goto set_ad;
     }
 
@@ -356,7 +356,7 @@ guest_walk_tables(struct vcpu *v, struct p2m_domain *p2m,
         start = _gfn((gfn_x(start) & ~GUEST_L2_GFN_MASK) +
                      guest_l1_table_offset(va));
         gw->l1e = guest_l1e_from_gfn(start, flags);
-        gw->l1mfn = _mfn(INVALID_MFN);
+        gw->l1mfn = INVALID_MFN;
     } 
     else 
     {
diff --git a/xen/arch/x86/mm/hap/hap.c b/xen/arch/x86/mm/hap/hap.c
index 9c2cd49..3218fa2 100644
--- a/xen/arch/x86/mm/hap/hap.c
+++ b/xen/arch/x86/mm/hap/hap.c
@@ -430,7 +430,7 @@ static mfn_t hap_make_monitor_table(struct vcpu *v)
  oom:
     HAP_ERROR("out of memory building monitor pagetable\n");
     domain_crash(d);
-    return _mfn(INVALID_MFN);
+    return INVALID_MFN;
 }
 
 static void hap_destroy_monitor_table(struct vcpu* v, mfn_t mmfn)
@@ -509,7 +509,7 @@ int hap_enable(struct domain *d, u32 mode)
         }
 
         for ( i = 0; i < MAX_EPTP; i++ )
-            d->arch.altp2m_eptp[i] = INVALID_MFN;
+            d->arch.altp2m_eptp[i] = mfn_x(INVALID_MFN);
 
         for ( i = 0; i < MAX_ALTP2M; i++ )
         {
diff --git a/xen/arch/x86/mm/p2m-ept.c b/xen/arch/x86/mm/p2m-ept.c
index 7166c71..6d03736 100644
--- a/xen/arch/x86/mm/p2m-ept.c
+++ b/xen/arch/x86/mm/p2m-ept.c
@@ -50,7 +50,7 @@ static int atomic_write_ept_entry(ept_entry_t *entryptr, ept_entry_t new,
                                   int level)
 {
     int rc;
-    unsigned long oldmfn = INVALID_MFN;
+    unsigned long oldmfn = mfn_x(INVALID_MFN);
     bool_t check_foreign = (new.mfn != entryptr->mfn ||
                             new.sa_p2mt != entryptr->sa_p2mt);
 
@@ -91,7 +91,7 @@ static int atomic_write_ept_entry(ept_entry_t *entryptr, ept_entry_t new,
 
     write_atomic(&entryptr->epte, new.epte);
 
-    if ( unlikely(oldmfn != INVALID_MFN) )
+    if ( unlikely(oldmfn != mfn_x(INVALID_MFN)) )
         put_page(mfn_to_page(oldmfn));
 
     rc = 0;
@@ -887,7 +887,7 @@ static mfn_t ept_get_entry(struct p2m_domain *p2m,
     int i;
     int ret = 0;
     bool_t recalc = 0;
-    mfn_t mfn = _mfn(INVALID_MFN);
+    mfn_t mfn = INVALID_MFN;
     struct ept_data *ept = &p2m->ept;
 
     *t = p2m_mmio_dm;
diff --git a/xen/arch/x86/mm/p2m-pod.c b/xen/arch/x86/mm/p2m-pod.c
index b7ab169..f384589 100644
--- a/xen/arch/x86/mm/p2m-pod.c
+++ b/xen/arch/x86/mm/p2m-pod.c
@@ -559,7 +559,7 @@ p2m_pod_decrease_reservation(struct domain *d,
     {
         /* All PoD: Mark the whole region invalid and tell caller
          * we're done. */
-        p2m_set_entry(p2m, gpfn, _mfn(INVALID_MFN), order, p2m_invalid,
+        p2m_set_entry(p2m, gpfn, INVALID_MFN, order, p2m_invalid,
                       p2m->default_access);
         p2m->pod.entry_count-=(1<<order);
         BUG_ON(p2m->pod.entry_count < 0);
@@ -602,7 +602,7 @@ p2m_pod_decrease_reservation(struct domain *d,
         n = 1UL << cur_order;
         if ( t == p2m_populate_on_demand )
         {
-            p2m_set_entry(p2m, gpfn + i, _mfn(INVALID_MFN), cur_order,
+            p2m_set_entry(p2m, gpfn + i, INVALID_MFN, cur_order,
                           p2m_invalid, p2m->default_access);
             p2m->pod.entry_count -= n;
             BUG_ON(p2m->pod.entry_count < 0);
@@ -624,7 +624,7 @@ p2m_pod_decrease_reservation(struct domain *d,
 
             page = mfn_to_page(mfn);
 
-            p2m_set_entry(p2m, gpfn + i, _mfn(INVALID_MFN), cur_order,
+            p2m_set_entry(p2m, gpfn + i, INVALID_MFN, cur_order,
                           p2m_invalid, p2m->default_access);
             p2m_tlb_flush_sync(p2m);
             for ( j = 0; j < n; ++j )
@@ -671,7 +671,7 @@ void p2m_pod_dump_data(struct domain *d)
 static int
 p2m_pod_zero_check_superpage(struct p2m_domain *p2m, unsigned long gfn)
 {
-    mfn_t mfn, mfn0 = _mfn(INVALID_MFN);
+    mfn_t mfn, mfn0 = INVALID_MFN;
     p2m_type_t type, type0 = 0;
     unsigned long * map = NULL;
     int ret=0, reset = 0;
@@ -754,7 +754,7 @@ p2m_pod_zero_check_superpage(struct p2m_domain *p2m, unsigned long gfn)
     }
 
     /* Try to remove the page, restoring old mapping if it fails. */
-    p2m_set_entry(p2m, gfn, _mfn(INVALID_MFN), PAGE_ORDER_2M,
+    p2m_set_entry(p2m, gfn, INVALID_MFN, PAGE_ORDER_2M,
                   p2m_populate_on_demand, p2m->default_access);
     p2m_tlb_flush_sync(p2m);
 
@@ -871,7 +871,7 @@ p2m_pod_zero_check(struct p2m_domain *p2m, unsigned long *gfns, int count)
         }
 
         /* Try to remove the page, restoring old mapping if it fails. */
-        p2m_set_entry(p2m, gfns[i], _mfn(INVALID_MFN), PAGE_ORDER_4K,
+        p2m_set_entry(p2m, gfns[i], INVALID_MFN, PAGE_ORDER_4K,
                       p2m_populate_on_demand, p2m->default_access);
 
         /* See if the page was successfully unmapped.  (Allow one refcount
@@ -1073,7 +1073,7 @@ p2m_pod_demand_populate(struct p2m_domain *p2m, unsigned long gfn,
          * NOTE: In a fine-grained p2m locking scenario this operation
          * may need to promote its locking from gfn->1g superpage
          */
-        p2m_set_entry(p2m, gfn_aligned, _mfn(INVALID_MFN), PAGE_ORDER_2M,
+        p2m_set_entry(p2m, gfn_aligned, INVALID_MFN, PAGE_ORDER_2M,
                       p2m_populate_on_demand, p2m->default_access);
         return 0;
     }
@@ -1157,7 +1157,7 @@ remap_and_retry:
      * need promoting the gfn lock from gfn->2M superpage */
     gfn_aligned = (gfn>>order)<<order;
     for(i=0; i<(1<<order); i++)
-        p2m_set_entry(p2m, gfn_aligned + i, _mfn(INVALID_MFN), PAGE_ORDER_4K,
+        p2m_set_entry(p2m, gfn_aligned + i, INVALID_MFN, PAGE_ORDER_4K,
                       p2m_populate_on_demand, p2m->default_access);
     if ( tb_init_done )
     {
@@ -1215,7 +1215,7 @@ guest_physmap_mark_populate_on_demand(struct domain *d, unsigned long gfn,
     }
 
     /* Now, actually do the two-way mapping */
-    rc = p2m_set_entry(p2m, gfn, _mfn(INVALID_MFN), order,
+    rc = p2m_set_entry(p2m, gfn, INVALID_MFN, order,
                        p2m_populate_on_demand, p2m->default_access);
     if ( rc == 0 )
     {
diff --git a/xen/arch/x86/mm/p2m-pt.c b/xen/arch/x86/mm/p2m-pt.c
index 4980934..2b6e89e 100644
--- a/xen/arch/x86/mm/p2m-pt.c
+++ b/xen/arch/x86/mm/p2m-pt.c
@@ -511,7 +511,7 @@ p2m_pt_set_entry(struct p2m_domain *p2m, unsigned long gfn, mfn_t mfn,
      * the intermediate one might be).
      */
     unsigned int flags, iommu_old_flags = 0;
-    unsigned long old_mfn = INVALID_MFN;
+    unsigned long old_mfn = mfn_x(INVALID_MFN);
 
     ASSERT(sve != 0);
 
@@ -764,7 +764,7 @@ p2m_pt_get_entry(struct p2m_domain *p2m, unsigned long gfn,
                      p2m->max_mapped_pfn )
                     break;
         }
-        return _mfn(INVALID_MFN);
+        return INVALID_MFN;
     }
 
     mfn = pagetable_get_mfn(p2m_get_pagetable(p2m));
@@ -777,7 +777,7 @@ p2m_pt_get_entry(struct p2m_domain *p2m, unsigned long gfn,
         if ( (l4e_get_flags(*l4e) & _PAGE_PRESENT) == 0 )
         {
             unmap_domain_page(l4e);
-            return _mfn(INVALID_MFN);
+            return INVALID_MFN;
         }
         mfn = _mfn(l4e_get_pfn(*l4e));
         recalc = needs_recalc(l4, *l4e);
@@ -805,7 +805,7 @@ pod_retry_l3:
                     *t = p2m_populate_on_demand;
             }
             unmap_domain_page(l3e);
-            return _mfn(INVALID_MFN);
+            return INVALID_MFN;
         }
         if ( flags & _PAGE_PSE )
         {
@@ -817,7 +817,7 @@ pod_retry_l3:
             unmap_domain_page(l3e);
 
             ASSERT(mfn_valid(mfn) || !p2m_is_ram(*t));
-            return (p2m_is_valid(*t)) ? mfn : _mfn(INVALID_MFN);
+            return (p2m_is_valid(*t)) ? mfn : INVALID_MFN;
         }
 
         mfn = _mfn(l3e_get_pfn(*l3e));
@@ -846,7 +846,7 @@ pod_retry_l2:
         }
     
         unmap_domain_page(l2e);
-        return _mfn(INVALID_MFN);
+        return INVALID_MFN;
     }
     if ( flags & _PAGE_PSE )
     {
@@ -856,7 +856,7 @@ pod_retry_l2:
         unmap_domain_page(l2e);
         
         ASSERT(mfn_valid(mfn) || !p2m_is_ram(*t));
-        return (p2m_is_valid(*t)) ? mfn : _mfn(INVALID_MFN);
+        return (p2m_is_valid(*t)) ? mfn : INVALID_MFN;
     }
 
     mfn = _mfn(l2e_get_pfn(*l2e));
@@ -885,14 +885,14 @@ pod_retry_l1:
         }
     
         unmap_domain_page(l1e);
-        return _mfn(INVALID_MFN);
+        return INVALID_MFN;
     }
     mfn = _mfn(l1e_get_pfn(*l1e));
     *t = recalc_type(recalc || _needs_recalc(flags), l1t, p2m, gfn);
     unmap_domain_page(l1e);
 
     ASSERT(mfn_valid(mfn) || !p2m_is_ram(*t) || p2m_is_paging(*t));
-    return (p2m_is_valid(*t) || p2m_is_grant(*t)) ? mfn : _mfn(INVALID_MFN);
+    return (p2m_is_valid(*t) || p2m_is_grant(*t)) ? mfn : INVALID_MFN;
 }
 
 static void p2m_pt_change_entry_type_global(struct p2m_domain *p2m,
diff --git a/xen/arch/x86/mm/p2m.c b/xen/arch/x86/mm/p2m.c
index 6258a5b..b93c8a2 100644
--- a/xen/arch/x86/mm/p2m.c
+++ b/xen/arch/x86/mm/p2m.c
@@ -388,7 +388,7 @@ mfn_t __get_gfn_type_access(struct p2m_domain *p2m, unsigned long gfn,
     if (unlikely((p2m_is_broken(*t))))
     {
         /* Return invalid_mfn to avoid caller's access */
-        mfn = _mfn(INVALID_MFN);
+        mfn = INVALID_MFN;
         if ( q & P2M_ALLOC )
             domain_crash(p2m->domain);
     }
@@ -493,8 +493,8 @@ int p2m_set_entry(struct p2m_domain *p2m, unsigned long gfn, mfn_t mfn,
             rc = set_rc;
 
         gfn += 1ul << order;
-        if ( mfn_x(mfn) != INVALID_MFN )
-            mfn = _mfn(mfn_x(mfn) + (1ul << order));
+        if ( !mfn_eq(mfn, INVALID_MFN) )
+            mfn = mfn_add(mfn, 1ul << order);
         todo -= 1ul << order;
     }
 
@@ -580,7 +580,7 @@ int p2m_alloc_table(struct p2m_domain *p2m)
 
     /* Initialise physmap tables for slot zero. Other code assumes this. */
     p2m->defer_nested_flush = 1;
-    rc = p2m_set_entry(p2m, 0, _mfn(INVALID_MFN), PAGE_ORDER_4K,
+    rc = p2m_set_entry(p2m, 0, INVALID_MFN, PAGE_ORDER_4K,
                        p2m_invalid, p2m->default_access);
     p2m->defer_nested_flush = 0;
     p2m_unlock(p2m);
@@ -670,7 +670,7 @@ p2m_remove_page(struct p2m_domain *p2m, unsigned long gfn, unsigned long mfn,
             ASSERT( !p2m_is_valid(t) || mfn + i == mfn_x(mfn_return) );
         }
     }
-    return p2m_set_entry(p2m, gfn, _mfn(INVALID_MFN), page_order, p2m_invalid,
+    return p2m_set_entry(p2m, gfn, INVALID_MFN, page_order, p2m_invalid,
                          p2m->default_access);
 }
 
@@ -840,7 +840,7 @@ guest_physmap_add_entry(struct domain *d, gfn_t gfn, mfn_t mfn,
     {
         gdprintk(XENLOG_WARNING, "Adding bad mfn to p2m map (%#lx -> %#lx)\n",
                  gfn_x(gfn), mfn_x(mfn));
-        rc = p2m_set_entry(p2m, gfn_x(gfn), _mfn(INVALID_MFN), page_order,
+        rc = p2m_set_entry(p2m, gfn_x(gfn), INVALID_MFN, page_order,
                            p2m_invalid, p2m->default_access);
         if ( rc == 0 )
         {
@@ -1107,7 +1107,7 @@ int clear_mmio_p2m_entry(struct domain *d, unsigned long gfn, mfn_t mfn,
     }
 
     /* Do not use mfn_valid() here as it will usually fail for MMIO pages. */
-    if ( (INVALID_MFN == mfn_x(actual_mfn)) || (t != p2m_mmio_direct) )
+    if ( mfn_eq(actual_mfn, INVALID_MFN) || (t != p2m_mmio_direct) )
     {
         gdprintk(XENLOG_ERR,
                  "gfn_to_mfn failed! gfn=%08lx type:%d\n", gfn, t);
@@ -1117,7 +1117,7 @@ int clear_mmio_p2m_entry(struct domain *d, unsigned long gfn, mfn_t mfn,
         gdprintk(XENLOG_WARNING,
                  "no mapping between mfn %08lx and gfn %08lx\n",
                  mfn_x(mfn), gfn);
-    rc = p2m_set_entry(p2m, gfn, _mfn(INVALID_MFN), order, p2m_invalid,
+    rc = p2m_set_entry(p2m, gfn, INVALID_MFN, order, p2m_invalid,
                        p2m->default_access);
 
  out:
@@ -1146,7 +1146,7 @@ int clear_identity_p2m_entry(struct domain *d, unsigned long gfn)
     mfn = p2m->get_entry(p2m, gfn, &p2mt, &a, 0, NULL, NULL);
     if ( p2mt == p2m_mmio_direct && mfn_x(mfn) == gfn )
     {
-        ret = p2m_set_entry(p2m, gfn, _mfn(INVALID_MFN), PAGE_ORDER_4K,
+        ret = p2m_set_entry(p2m, gfn, INVALID_MFN, PAGE_ORDER_4K,
                             p2m_invalid, p2m->default_access);
         gfn_unlock(p2m, gfn, 0);
     }
@@ -1316,7 +1316,7 @@ int p2m_mem_paging_evict(struct domain *d, unsigned long gfn)
         put_page(page);
 
     /* Remove mapping from p2m table */
-    ret = p2m_set_entry(p2m, gfn, _mfn(INVALID_MFN), PAGE_ORDER_4K,
+    ret = p2m_set_entry(p2m, gfn, INVALID_MFN, PAGE_ORDER_4K,
                         p2m_ram_paged, a);
 
     /* Clear content before returning the page to Xen */
@@ -1844,7 +1844,7 @@ long p2m_set_mem_access(struct domain *d, gfn_t gfn, uint32_t nr,
     if ( altp2m_idx )
     {
         if ( altp2m_idx >= MAX_ALTP2M ||
-             d->arch.altp2m_eptp[altp2m_idx] == INVALID_MFN )
+             d->arch.altp2m_eptp[altp2m_idx] == mfn_x(INVALID_MFN) )
             return -EINVAL;
 
         ap2m = d->arch.altp2m_p2m[altp2m_idx];
@@ -1942,7 +1942,7 @@ int p2m_get_mem_access(struct domain *d, gfn_t gfn, xenmem_access_t *access)
     mfn = p2m->get_entry(p2m, gfn_x(gfn), &t, &a, 0, NULL, NULL);
     gfn_unlock(p2m, gfn, 0);
 
-    if ( mfn_x(mfn) == INVALID_MFN )
+    if ( mfn_eq(mfn, INVALID_MFN) )
         return -ESRCH;
     
     if ( (unsigned) a >= ARRAY_SIZE(memaccess) )
@@ -2288,7 +2288,7 @@ unsigned int p2m_find_altp2m_by_eptp(struct domain *d, uint64_t eptp)
 
     for ( i = 0; i < MAX_ALTP2M; i++ )
     {
-        if ( d->arch.altp2m_eptp[i] == INVALID_MFN )
+        if ( d->arch.altp2m_eptp[i] == mfn_x(INVALID_MFN) )
             continue;
 
         p2m = d->arch.altp2m_p2m[i];
@@ -2315,7 +2315,7 @@ bool_t p2m_switch_vcpu_altp2m_by_id(struct vcpu *v, unsigned int idx)
 
     altp2m_list_lock(d);
 
-    if ( d->arch.altp2m_eptp[idx] != INVALID_MFN )
+    if ( d->arch.altp2m_eptp[idx] != mfn_x(INVALID_MFN) )
     {
         if ( idx != vcpu_altp2m(v).p2midx )
         {
@@ -2359,14 +2359,14 @@ bool_t p2m_altp2m_lazy_copy(struct vcpu *v, paddr_t gpa,
                               0, &page_order);
     __put_gfn(*ap2m, gfn_x(gfn));
 
-    if ( mfn_x(mfn) != INVALID_MFN )
+    if ( !mfn_eq(mfn, INVALID_MFN) )
         return 0;
 
     mfn = get_gfn_type_access(hp2m, gfn_x(gfn), &p2mt, &p2ma,
                               P2M_ALLOC | P2M_UNSHARE, &page_order);
     __put_gfn(hp2m, gfn_x(gfn));
 
-    if ( mfn_x(mfn) == INVALID_MFN )
+    if ( mfn_eq(mfn, INVALID_MFN) )
         return 0;
 
     p2m_lock(*ap2m);
@@ -2404,7 +2404,7 @@ void p2m_flush_altp2m(struct domain *d)
         /* Uninit and reinit ept to force TLB shootdown */
         ept_p2m_uninit(d->arch.altp2m_p2m[i]);
         ept_p2m_init(d->arch.altp2m_p2m[i]);
-        d->arch.altp2m_eptp[i] = INVALID_MFN;
+        d->arch.altp2m_eptp[i] = mfn_x(INVALID_MFN);
     }
 
     altp2m_list_unlock(d);
@@ -2431,7 +2431,7 @@ int p2m_init_altp2m_by_id(struct domain *d, unsigned int idx)
 
     altp2m_list_lock(d);
 
-    if ( d->arch.altp2m_eptp[idx] == INVALID_MFN )
+    if ( d->arch.altp2m_eptp[idx] == mfn_x(INVALID_MFN) )
     {
         p2m_init_altp2m_helper(d, idx);
         rc = 0;
@@ -2450,7 +2450,7 @@ int p2m_init_next_altp2m(struct domain *d, uint16_t *idx)
 
     for ( i = 0; i < MAX_ALTP2M; i++ )
     {
-        if ( d->arch.altp2m_eptp[i] != INVALID_MFN )
+        if ( d->arch.altp2m_eptp[i] != mfn_x(INVALID_MFN) )
             continue;
 
         p2m_init_altp2m_helper(d, i);
@@ -2476,7 +2476,7 @@ int p2m_destroy_altp2m_by_id(struct domain *d, unsigned int idx)
 
     altp2m_list_lock(d);
 
-    if ( d->arch.altp2m_eptp[idx] != INVALID_MFN )
+    if ( d->arch.altp2m_eptp[idx] != mfn_x(INVALID_MFN) )
     {
         p2m = d->arch.altp2m_p2m[idx];
 
@@ -2486,7 +2486,7 @@ int p2m_destroy_altp2m_by_id(struct domain *d, unsigned int idx)
             /* Uninit and reinit ept to force TLB shootdown */
             ept_p2m_uninit(d->arch.altp2m_p2m[idx]);
             ept_p2m_init(d->arch.altp2m_p2m[idx]);
-            d->arch.altp2m_eptp[idx] = INVALID_MFN;
+            d->arch.altp2m_eptp[idx] = mfn_x(INVALID_MFN);
             rc = 0;
         }
     }
@@ -2510,7 +2510,7 @@ int p2m_switch_domain_altp2m_by_id(struct domain *d, unsigned int idx)
 
     altp2m_list_lock(d);
 
-    if ( d->arch.altp2m_eptp[idx] != INVALID_MFN )
+    if ( d->arch.altp2m_eptp[idx] != mfn_x(INVALID_MFN) )
     {
         for_each_vcpu( d, v )
             if ( idx != vcpu_altp2m(v).p2midx )
@@ -2541,7 +2541,7 @@ int p2m_change_altp2m_gfn(struct domain *d, unsigned int idx,
     unsigned int page_order;
     int rc = -EINVAL;
 
-    if ( idx >= MAX_ALTP2M || d->arch.altp2m_eptp[idx] == INVALID_MFN )
+    if ( idx >= MAX_ALTP2M || d->arch.altp2m_eptp[idx] == mfn_x(INVALID_MFN) )
         return rc;
 
     hp2m = p2m_get_hostp2m(d);
@@ -2636,14 +2636,14 @@ void p2m_altp2m_propagate_change(struct domain *d, gfn_t gfn,
 
     for ( i = 0; i < MAX_ALTP2M; i++ )
     {
-        if ( d->arch.altp2m_eptp[i] == INVALID_MFN )
+        if ( d->arch.altp2m_eptp[i] == mfn_x(INVALID_MFN) )
             continue;
 
         p2m = d->arch.altp2m_p2m[i];
         m = get_gfn_type_access(p2m, gfn_x(gfn), &t, &a, 0, NULL);
 
         /* Check for a dropped page that may impact this altp2m */
-        if ( mfn_x(mfn) == INVALID_MFN &&
+        if ( mfn_eq(mfn, INVALID_MFN) &&
              gfn_x(gfn) >= p2m->min_remapped_gfn &&
              gfn_x(gfn) <= p2m->max_remapped_gfn )
         {
@@ -2660,7 +2660,7 @@ void p2m_altp2m_propagate_change(struct domain *d, gfn_t gfn,
                 for ( i = 0; i < MAX_ALTP2M; i++ )
                 {
                     if ( i == last_reset_idx ||
-                         d->arch.altp2m_eptp[i] == INVALID_MFN )
+                         d->arch.altp2m_eptp[i] == mfn_x(INVALID_MFN) )
                         continue;
 
                     p2m = d->arch.altp2m_p2m[i];
@@ -2672,7 +2672,7 @@ void p2m_altp2m_propagate_change(struct domain *d, gfn_t gfn,
                 goto out;
             }
         }
-        else if ( mfn_x(m) != INVALID_MFN )
+        else if ( !mfn_eq(m, INVALID_MFN) )
             p2m_set_entry(p2m, gfn_x(gfn), mfn, page_order, p2mt, p2ma);
 
         __put_gfn(p2m, gfn_x(gfn));
diff --git a/xen/arch/x86/mm/paging.c b/xen/arch/x86/mm/paging.c
index 8219bb6..107fc8c 100644
--- a/xen/arch/x86/mm/paging.c
+++ b/xen/arch/x86/mm/paging.c
@@ -67,7 +67,7 @@ static mfn_t paging_new_log_dirty_page(struct domain *d)
     if ( unlikely(page == NULL) )
     {
         d->arch.paging.log_dirty.failed_allocs++;
-        return _mfn(INVALID_MFN);
+        return INVALID_MFN;
     }
 
     d->arch.paging.log_dirty.allocs++;
@@ -95,7 +95,7 @@ static mfn_t paging_new_log_dirty_node(struct domain *d)
         int i;
         mfn_t *node = map_domain_page(mfn);
         for ( i = 0; i < LOGDIRTY_NODE_ENTRIES; i++ )
-            node[i] = _mfn(INVALID_MFN);
+            node[i] = INVALID_MFN;
         unmap_domain_page(node);
     }
     return mfn;
@@ -167,7 +167,7 @@ static int paging_free_log_dirty_bitmap(struct domain *d, int rc)
 
             unmap_domain_page(l2);
             paging_free_log_dirty_page(d, l3[i3]);
-            l3[i3] = _mfn(INVALID_MFN);
+            l3[i3] = INVALID_MFN;
 
             if ( i3 < LOGDIRTY_NODE_ENTRIES - 1 && hypercall_preempt_check() )
             {
@@ -182,7 +182,7 @@ static int paging_free_log_dirty_bitmap(struct domain *d, int rc)
         if ( rc )
             break;
         paging_free_log_dirty_page(d, l4[i4]);
-        l4[i4] = _mfn(INVALID_MFN);
+        l4[i4] = INVALID_MFN;
 
         if ( i4 < LOGDIRTY_NODE_ENTRIES - 1 && hypercall_preempt_check() )
         {
@@ -198,7 +198,7 @@ static int paging_free_log_dirty_bitmap(struct domain *d, int rc)
     if ( !rc )
     {
         paging_free_log_dirty_page(d, d->arch.paging.log_dirty.top);
-        d->arch.paging.log_dirty.top = _mfn(INVALID_MFN);
+        d->arch.paging.log_dirty.top = INVALID_MFN;
 
         ASSERT(d->arch.paging.log_dirty.allocs == 0);
         d->arch.paging.log_dirty.failed_allocs = 0;
@@ -660,7 +660,7 @@ int paging_domain_init(struct domain *d, unsigned int domcr_flags)
     /* This must be initialized separately from the rest of the
      * log-dirty init code as that can be called more than once and we
      * don't want to leak any active log-dirty bitmaps */
-    d->arch.paging.log_dirty.top = _mfn(INVALID_MFN);
+    d->arch.paging.log_dirty.top = INVALID_MFN;
 
     /*
      * Shadow pagetables are the default, but we will use
diff --git a/xen/arch/x86/mm/shadow/common.c b/xen/arch/x86/mm/shadow/common.c
index 226e32d..1c0b6cd 100644
--- a/xen/arch/x86/mm/shadow/common.c
+++ b/xen/arch/x86/mm/shadow/common.c
@@ -88,10 +88,10 @@ void shadow_vcpu_init(struct vcpu *v)
 
     for ( i = 0; i < SHADOW_OOS_PAGES; i++ )
     {
-        v->arch.paging.shadow.oos[i] = _mfn(INVALID_MFN);
-        v->arch.paging.shadow.oos_snapshot[i] = _mfn(INVALID_MFN);
+        v->arch.paging.shadow.oos[i] = INVALID_MFN;
+        v->arch.paging.shadow.oos_snapshot[i] = INVALID_MFN;
         for ( j = 0; j < SHADOW_OOS_FIXUPS; j++ )
-            v->arch.paging.shadow.oos_fixup[i].smfn[j] = _mfn(INVALID_MFN);
+            v->arch.paging.shadow.oos_fixup[i].smfn[j] = INVALID_MFN;
     }
 #endif
 
@@ -593,12 +593,12 @@ static inline int oos_fixup_flush_gmfn(struct vcpu *v, mfn_t gmfn,
     int i;
     for ( i = 0; i < SHADOW_OOS_FIXUPS; i++ )
     {
-        if ( mfn_x(fixup->smfn[i]) != INVALID_MFN )
+        if ( !mfn_eq(fixup->smfn[i], INVALID_MFN) )
         {
             sh_remove_write_access_from_sl1p(d, gmfn,
                                              fixup->smfn[i],
                                              fixup->off[i]);
-            fixup->smfn[i] = _mfn(INVALID_MFN);
+            fixup->smfn[i] = INVALID_MFN;
         }
     }
 
@@ -636,7 +636,7 @@ void oos_fixup_add(struct domain *d, mfn_t gmfn,
 
             next = oos_fixup[idx].next;
 
-            if ( mfn_x(oos_fixup[idx].smfn[next]) != INVALID_MFN )
+            if ( !mfn_eq(oos_fixup[idx].smfn[next], INVALID_MFN) )
             {
                 TRACE_SHADOW_PATH_FLAG(TRCE_SFLAG_OOS_FIXUP_EVICT);
 
@@ -757,7 +757,7 @@ static void oos_hash_add(struct vcpu *v, mfn_t gmfn)
     struct oos_fixup fixup = { .next = 0 };
 
     for (i = 0; i < SHADOW_OOS_FIXUPS; i++ )
-        fixup.smfn[i] = _mfn(INVALID_MFN);
+        fixup.smfn[i] = INVALID_MFN;
 
     idx = mfn_x(gmfn) % SHADOW_OOS_PAGES;
     oidx = idx;
@@ -807,7 +807,7 @@ static void oos_hash_remove(struct domain *d, mfn_t gmfn)
             idx = (idx + 1) % SHADOW_OOS_PAGES;
         if ( mfn_x(oos[idx]) == mfn_x(gmfn) )
         {
-            oos[idx] = _mfn(INVALID_MFN);
+            oos[idx] = INVALID_MFN;
             return;
         }
     }
@@ -838,7 +838,6 @@ mfn_t oos_snapshot_lookup(struct domain *d, mfn_t gmfn)
 
     SHADOW_ERROR("gmfn %lx was OOS but not in hash table\n", mfn_x(gmfn));
     BUG();
-    return _mfn(INVALID_MFN);
 }
 
 /* Pull a single guest page back into sync */
@@ -862,7 +861,7 @@ void sh_resync(struct domain *d, mfn_t gmfn)
         if ( mfn_x(oos[idx]) == mfn_x(gmfn) )
         {
             _sh_resync(v, gmfn, &oos_fixup[idx], oos_snapshot[idx]);
-            oos[idx] = _mfn(INVALID_MFN);
+            oos[idx] = INVALID_MFN;
             return;
         }
     }
@@ -914,7 +913,7 @@ void sh_resync_all(struct vcpu *v, int skip, int this, int others)
         {
             /* Write-protect and sync contents */
             _sh_resync(v, oos[idx], &oos_fixup[idx], oos_snapshot[idx]);
-            oos[idx] = _mfn(INVALID_MFN);
+            oos[idx] = INVALID_MFN;
         }
 
  resync_others:
@@ -948,7 +947,7 @@ void sh_resync_all(struct vcpu *v, int skip, int this, int others)
             {
                 /* Write-protect and sync contents */
                 _sh_resync(other, oos[idx], &oos_fixup[idx], oos_snapshot[idx]);
-                oos[idx] = _mfn(INVALID_MFN);
+                oos[idx] = INVALID_MFN;
             }
         }
     }
@@ -1784,7 +1783,7 @@ void *sh_emulate_map_dest(struct vcpu *v, unsigned long vaddr,
     if ( likely(((vaddr + bytes - 1) & PAGE_MASK) == (vaddr & PAGE_MASK)) )
     {
         /* Whole write fits on a single page. */
-        sh_ctxt->mfn[1] = _mfn(INVALID_MFN);
+        sh_ctxt->mfn[1] = INVALID_MFN;
         map = map_domain_page(sh_ctxt->mfn[0]) + (vaddr & ~PAGE_MASK);
     }
     else if ( !is_hvm_domain(d) )
@@ -2086,7 +2085,7 @@ mfn_t shadow_hash_lookup(struct domain *d, unsigned long n, unsigned int t)
     }
 
     perfc_incr(shadow_hash_lookup_miss);
-    return _mfn(INVALID_MFN);
+    return INVALID_MFN;
 }
 
 void shadow_hash_insert(struct domain *d, unsigned long n, unsigned int t,
@@ -2910,7 +2909,7 @@ void sh_reset_l3_up_pointers(struct vcpu *v)
     };
     static const unsigned int callback_mask = SHF_L3_64;
 
-    hash_vcpu_foreach(v, callback_mask, callbacks, _mfn(INVALID_MFN));
+    hash_vcpu_foreach(v, callback_mask, callbacks, INVALID_MFN);
 }
 
 
@@ -2940,7 +2939,7 @@ static void sh_update_paging_modes(struct vcpu *v)
 #endif /* (SHADOW_OPTIMIZATIONS & SHOPT_VIRTUAL_TLB) */
 
 #if (SHADOW_OPTIMIZATIONS & SHOPT_OUT_OF_SYNC)
-    if ( mfn_x(v->arch.paging.shadow.oos_snapshot[0]) == INVALID_MFN )
+    if ( mfn_eq(v->arch.paging.shadow.oos_snapshot[0], INVALID_MFN) )
     {
         int i;
         for(i = 0; i < SHADOW_OOS_PAGES; i++)
@@ -3284,7 +3283,7 @@ void shadow_teardown(struct domain *d, int *preempted)
                 if ( mfn_valid(oos_snapshot[i]) )
                 {
                     shadow_free(d, oos_snapshot[i]);
-                    oos_snapshot[i] = _mfn(INVALID_MFN);
+                    oos_snapshot[i] = INVALID_MFN;
                 }
         }
 #endif /* OOS */
@@ -3449,7 +3448,7 @@ static int shadow_one_bit_disable(struct domain *d, u32 mode)
                     if ( mfn_valid(oos_snapshot[i]) )
                     {
                         shadow_free(d, oos_snapshot[i]);
-                        oos_snapshot[i] = _mfn(INVALID_MFN);
+                        oos_snapshot[i] = INVALID_MFN;
                     }
             }
 #endif /* OOS */
@@ -3744,7 +3743,7 @@ int shadow_track_dirty_vram(struct domain *d,
         memcpy(dirty_bitmap, dirty_vram->dirty_bitmap, dirty_size);
     else
     {
-        unsigned long map_mfn = INVALID_MFN;
+        unsigned long map_mfn = mfn_x(INVALID_MFN);
         void *map_sl1p = NULL;
 
         /* Iterate over VRAM to track dirty bits. */
@@ -3754,7 +3753,7 @@ int shadow_track_dirty_vram(struct domain *d,
             int dirty = 0;
             paddr_t sl1ma = dirty_vram->sl1ma[i];
 
-            if (mfn_x(mfn) == INVALID_MFN)
+            if ( !mfn_eq(mfn, INVALID_MFN) )
             {
                 dirty = 1;
             }
@@ -3830,7 +3829,7 @@ int shadow_track_dirty_vram(struct domain *d,
             for ( i = begin_pfn; i < end_pfn; i++ )
             {
                 mfn_t mfn = get_gfn_query_unlocked(d, i, &t);
-                if ( mfn_x(mfn) != INVALID_MFN )
+                if ( !mfn_eq(mfn, INVALID_MFN) )
                     flush_tlb |= sh_remove_write_access(d, mfn, 1, 0);
             }
             dirty_vram->last_dirty = -1;
@@ -3968,7 +3967,7 @@ void shadow_audit_tables(struct vcpu *v)
         }
     }
 
-    hash_vcpu_foreach(v, mask, callbacks, _mfn(INVALID_MFN));
+    hash_vcpu_foreach(v, mask, callbacks, INVALID_MFN_T);
 }
 
 #endif /* Shadow audit */
diff --git a/xen/arch/x86/mm/shadow/multi.c b/xen/arch/x86/mm/shadow/multi.c
index dfe59a2..f892e2f 100644
--- a/xen/arch/x86/mm/shadow/multi.c
+++ b/xen/arch/x86/mm/shadow/multi.c
@@ -177,7 +177,7 @@ sh_walk_guest_tables(struct vcpu *v, unsigned long va, walk_t *gw,
 {
     return guest_walk_tables(v, p2m_get_hostp2m(v->domain), va, gw, pfec,
 #if GUEST_PAGING_LEVELS == 3 /* PAE */
-                             _mfn(INVALID_MFN),
+                             INVALID_MFN,
                              v->arch.paging.shadow.gl3e
 #else /* 32 or 64 */
                              pagetable_get_mfn(v->arch.guest_table),
@@ -336,32 +336,32 @@ static void sh_audit_gw(struct vcpu *v, walk_t *gw)
     if ( mfn_valid(gw->l4mfn)
          && mfn_valid((smfn = get_shadow_status(d, gw->l4mfn,
                                                 SH_type_l4_shadow))) )
-        (void) sh_audit_l4_table(v, smfn, _mfn(INVALID_MFN));
+        (void) sh_audit_l4_table(v, smfn, INVALID_MFN);
     if ( mfn_valid(gw->l3mfn)
          && mfn_valid((smfn = get_shadow_status(d, gw->l3mfn,
                                                 SH_type_l3_shadow))) )
-        (void) sh_audit_l3_table(v, smfn, _mfn(INVALID_MFN));
+        (void) sh_audit_l3_table(v, smfn, INVALID_MFN);
 #endif /* PAE or 64... */
     if ( mfn_valid(gw->l2mfn) )
     {
         if ( mfn_valid((smfn = get_shadow_status(d, gw->l2mfn,
                                                  SH_type_l2_shadow))) )
-            (void) sh_audit_l2_table(v, smfn, _mfn(INVALID_MFN));
+            (void) sh_audit_l2_table(v, smfn, INVALID_MFN);
 #if GUEST_PAGING_LEVELS == 3
         if ( mfn_valid((smfn = get_shadow_status(d, gw->l2mfn,
                                                  SH_type_l2h_shadow))) )
-            (void) sh_audit_l2_table(v, smfn, _mfn(INVALID_MFN));
+            (void) sh_audit_l2_table(v, smfn, INVALID_MFN);
 #endif
     }
     if ( mfn_valid(gw->l1mfn)
          && mfn_valid((smfn = get_shadow_status(d, gw->l1mfn,
                                                 SH_type_l1_shadow))) )
-        (void) sh_audit_l1_table(v, smfn, _mfn(INVALID_MFN));
+        (void) sh_audit_l1_table(v, smfn, INVALID_MFN);
     else if ( (guest_l2e_get_flags(gw->l2e) & _PAGE_PRESENT)
               && (guest_l2e_get_flags(gw->l2e) & _PAGE_PSE)
               && mfn_valid(
               (smfn = get_fl1_shadow_status(d, guest_l2e_get_gfn(gw->l2e)))) )
-        (void) sh_audit_fl1_table(v, smfn, _mfn(INVALID_MFN));
+        (void) sh_audit_fl1_table(v, smfn, INVALID_MFN);
 }
 
 #else
@@ -1752,7 +1752,7 @@ static shadow_l2e_t * shadow_get_and_create_l2e(struct vcpu *v,
 {
 #if GUEST_PAGING_LEVELS >= 4 /* 64bit... */
     struct domain *d = v->domain;
-    mfn_t sl3mfn = _mfn(INVALID_MFN);
+    mfn_t sl3mfn = INVALID_MFN;
     shadow_l3e_t *sl3e;
     if ( !mfn_valid(gw->l2mfn) ) return NULL; /* No guest page. */
     /* Get the l3e */
@@ -2158,7 +2158,7 @@ static int validate_gl4e(struct vcpu *v, void *new_ge, mfn_t sl4mfn, void *se)
     shadow_l4e_t new_sl4e;
     guest_l4e_t new_gl4e = *(guest_l4e_t *)new_ge;
     shadow_l4e_t *sl4p = se;
-    mfn_t sl3mfn = _mfn(INVALID_MFN);
+    mfn_t sl3mfn = INVALID_MFN;
     struct domain *d = v->domain;
     p2m_type_t p2mt;
     int result = 0;
@@ -2217,7 +2217,7 @@ static int validate_gl3e(struct vcpu *v, void *new_ge, mfn_t sl3mfn, void *se)
     shadow_l3e_t new_sl3e;
     guest_l3e_t new_gl3e = *(guest_l3e_t *)new_ge;
     shadow_l3e_t *sl3p = se;
-    mfn_t sl2mfn = _mfn(INVALID_MFN);
+    mfn_t sl2mfn = INVALID_MFN;
     p2m_type_t p2mt;
     int result = 0;
 
@@ -2250,7 +2250,7 @@ static int validate_gl2e(struct vcpu *v, void *new_ge, mfn_t sl2mfn, void *se)
     shadow_l2e_t new_sl2e;
     guest_l2e_t new_gl2e = *(guest_l2e_t *)new_ge;
     shadow_l2e_t *sl2p = se;
-    mfn_t sl1mfn = _mfn(INVALID_MFN);
+    mfn_t sl1mfn = INVALID_MFN;
     p2m_type_t p2mt;
     int result = 0;
 
@@ -2608,7 +2608,7 @@ static inline void check_for_early_unshadow(struct vcpu *v, mfn_t gmfn)
 static inline void reset_early_unshadow(struct vcpu *v)
 {
 #if SHADOW_OPTIMIZATIONS & SHOPT_EARLY_UNSHADOW
-    v->arch.paging.shadow.last_emulated_mfn_for_unshadow = INVALID_MFN;
+    v->arch.paging.shadow.last_emulated_mfn_for_unshadow = mfn_x(INVALID_MFN);
 #endif
 }
 
@@ -4105,10 +4105,10 @@ sh_update_cr3(struct vcpu *v, int do_locking)
                                            ? SH_type_l2h_shadow
                                            : SH_type_l2_shadow);
                 else
-                    sh_set_toplevel_shadow(v, i, _mfn(INVALID_MFN), 0);
+                    sh_set_toplevel_shadow(v, i, INVALID_MFN, 0);
             }
             else
-                sh_set_toplevel_shadow(v, i, _mfn(INVALID_MFN), 0);
+                sh_set_toplevel_shadow(v, i, INVALID_MFN, 0);
         }
     }
 #elif GUEST_PAGING_LEVELS == 4
@@ -4531,7 +4531,7 @@ static void sh_pagetable_dying(struct vcpu *v, paddr_t gpa)
 
         if ( fast_path ) {
             if ( pagetable_is_null(v->arch.shadow_table[i]) )
-                smfn = _mfn(INVALID_MFN);
+                smfn = INVALID_MFN;
             else
                 smfn = _mfn(pagetable_get_pfn(v->arch.shadow_table[i]));
         }
@@ -4540,8 +4540,8 @@ static void sh_pagetable_dying(struct vcpu *v, paddr_t gpa)
             /* retrieving the l2s */
             gmfn = get_gfn_query_unlocked(d, gfn_x(guest_l3e_get_gfn(gl3e[i])),
                                           &p2mt);
-            smfn = unlikely(mfn_x(gmfn) == INVALID_MFN)
-                   ? _mfn(INVALID_MFN)
+            smfn = unlikely(mfn_eq(gmfn, INVALID_MFN))
+                   ? INVALID_MFN
                    : shadow_hash_lookup(d, mfn_x(gmfn), SH_type_l2_pae_shadow);
         }
 
@@ -4846,7 +4846,7 @@ int sh_audit_fl1_table(struct vcpu *v, mfn_t sl1mfn, mfn_t x)
 {
     guest_l1e_t *gl1e, e;
     shadow_l1e_t *sl1e;
-    mfn_t gl1mfn = _mfn(INVALID_MFN);
+    mfn_t gl1mfn = INVALID_MFN;
     int f;
     int done = 0;
 
diff --git a/xen/common/domain.c b/xen/common/domain.c
index 45273d4..42c07ee 100644
--- a/xen/common/domain.c
+++ b/xen/common/domain.c
@@ -117,7 +117,7 @@ static void vcpu_info_reset(struct vcpu *v)
     v->vcpu_info = ((v->vcpu_id < XEN_LEGACY_MAX_VCPUS)
                     ? (vcpu_info_t *)&shared_info(d, vcpu_info[v->vcpu_id])
                     : &dummy_vcpu_info);
-    v->vcpu_info_mfn = INVALID_MFN;
+    v->vcpu_info_mfn = mfn_x(INVALID_MFN);
 }
 
 struct vcpu *alloc_vcpu(
@@ -1141,7 +1141,7 @@ int map_vcpu_info(struct vcpu *v, unsigned long gfn, unsigned offset)
     if ( offset > (PAGE_SIZE - sizeof(vcpu_info_t)) )
         return -EINVAL;
 
-    if ( v->vcpu_info_mfn != INVALID_MFN )
+    if ( v->vcpu_info_mfn != mfn_x(INVALID_MFN) )
         return -EINVAL;
 
     /* Run this command on yourself or on other offline VCPUS. */
@@ -1205,7 +1205,7 @@ void unmap_vcpu_info(struct vcpu *v)
 {
     unsigned long mfn;
 
-    if ( v->vcpu_info_mfn == INVALID_MFN )
+    if ( v->vcpu_info_mfn == mfn_x(INVALID_MFN) )
         return;
 
     mfn = v->vcpu_info_mfn;
diff --git a/xen/common/grant_table.c b/xen/common/grant_table.c
index 3f15543..ecace07 100644
--- a/xen/common/grant_table.c
+++ b/xen/common/grant_table.c
@@ -244,7 +244,7 @@ static int __get_paged_frame(unsigned long gfn, unsigned long *frame, struct pag
                               (readonly) ? P2M_ALLOC : P2M_UNSHARE);
     if ( !(*page) )
     {
-        *frame = INVALID_MFN;
+        *frame = mfn_x(INVALID_MFN);
         if ( p2m_is_shared(p2mt) )
             return GNTST_eagain;
         if ( p2m_is_paging(p2mt) )
@@ -260,7 +260,7 @@ static int __get_paged_frame(unsigned long gfn, unsigned long *frame, struct pag
     *page = mfn_valid(*frame) ? mfn_to_page(*frame) : NULL;
     if ( (!(*page)) || (!get_page(*page, rd)) )
     {
-        *frame = INVALID_MFN;
+        *frame = mfn_x(INVALID_MFN);
         *page = NULL;
         rc = GNTST_bad_page;
     }
@@ -1785,7 +1785,7 @@ gnttab_transfer(
             p2m_type_t __p2mt;
             mfn = mfn_x(get_gfn_unshare(d, gop.mfn, &__p2mt));
             if ( p2m_is_shared(__p2mt) || !p2m_is_valid(__p2mt) )
-                mfn = INVALID_MFN;
+                mfn = mfn_x(INVALID_MFN);
         }
 #else
         mfn = mfn_x(gfn_to_mfn(d, _gfn(gop.mfn)));
diff --git a/xen/include/xen/mm.h b/xen/include/xen/mm.h
index afbb1a1..7f207ec 100644
--- a/xen/include/xen/mm.h
+++ b/xen/include/xen/mm.h
@@ -55,7 +55,7 @@
 
 TYPE_SAFE(unsigned long, mfn);
 #define PRI_mfn          "05lx"
-#define INVALID_MFN      (~0UL)
+#define INVALID_MFN      _mfn(~0UL)
 
 #ifndef mfn_t
 #define mfn_t /* Grep fodder: mfn_t, _mfn() and mfn_x() are defined above */
