diff --git a/xen/arch/arm/p2m.c b/xen/arch/arm/p2m.c
index d690602..c938dde 100644
--- a/xen/arch/arm/p2m.c
+++ b/xen/arch/arm/p2m.c
@@ -479,7 +479,7 @@ static int __p2m_get_mem_access(struct domain *d, gfn_t gfn,
     }
 
     /* If request to get default access. */
-    if ( gfn_x(gfn) == INVALID_GFN )
+    if ( gfn_eq(gfn, INVALID_GFN) )
     {
         *access = memaccess[p2m->default_access];
         return 0;
@@ -1879,7 +1879,7 @@ long p2m_set_mem_access(struct domain *d, gfn_t gfn, uint32_t nr,
     p2m->mem_access_enabled = true;
 
     /* If request to set default access. */
-    if ( gfn_x(gfn) == INVALID_GFN )
+    if ( gfn_eq(gfn, INVALID_GFN) )
     {
         p2m->default_access = a;
         return 0;
diff --git a/xen/arch/x86/debug.c b/xen/arch/x86/debug.c
index 9213ea7..3030022 100644
--- a/xen/arch/x86/debug.c
+++ b/xen/arch/x86/debug.c
@@ -44,8 +44,7 @@ typedef unsigned char dbgbyte_t;
 
 /* Returns: mfn for the given (hvm guest) vaddr */
 static mfn_t
-dbg_hvm_va2mfn(dbgva_t vaddr, struct domain *dp, int toaddr,
-                unsigned long *gfn)
+dbg_hvm_va2mfn(dbgva_t vaddr, struct domain *dp, int toaddr, gfn_t *gfn)
 {
     mfn_t mfn;
     uint32_t pfec = PFEC_page_present;
@@ -53,14 +52,14 @@ dbg_hvm_va2mfn(dbgva_t vaddr, struct domain *dp, int toaddr,
 
     DBGP2("vaddr:%lx domid:%d\n", vaddr, dp->domain_id);
 
-    *gfn = paging_gva_to_gfn(dp->vcpu[0], vaddr, &pfec);
-    if ( *gfn == INVALID_GFN )
+    *gfn = _gfn(paging_gva_to_gfn(dp->vcpu[0], vaddr, &pfec));
+    if ( gfn_eq(*gfn, INVALID_GFN) )
     {
         DBGP2("kdb:bad gfn from gva_to_gfn\n");
         return INVALID_MFN;
     }
 
-    mfn = get_gfn(dp, *gfn, &gfntype);
+    mfn = get_gfn(dp, gfn_x(*gfn), &gfntype);
     if ( p2m_is_readonly(gfntype) && toaddr )
     {
         DBGP2("kdb:p2m_is_readonly: gfntype:%x\n", gfntype);
@@ -72,7 +71,7 @@ dbg_hvm_va2mfn(dbgva_t vaddr, struct domain *dp, int toaddr,
 
     if ( mfn_eq(mfn, INVALID_MFN) )
     {
-        put_gfn(dp, *gfn);
+        put_gfn(dp, gfn_x(*gfn));
         *gfn = INVALID_GFN;
     }
 
@@ -165,7 +164,8 @@ unsigned int dbg_rw_guest_mem(struct domain *dp, void * __user gaddr,
         char *va;
         unsigned long addr = (unsigned long)gaddr;
         mfn_t mfn;
-        unsigned long gfn = INVALID_GFN, pagecnt;
+        gfn_t gfn = INVALID_GFN;
+        unsigned long pagecnt;
 
         pagecnt = min_t(long, PAGE_SIZE - (addr & ~PAGE_MASK), len);
 
@@ -189,8 +189,8 @@ unsigned int dbg_rw_guest_mem(struct domain *dp, void * __user gaddr,
         }
 
         unmap_domain_page(va);
-        if ( gfn != INVALID_GFN )
-            put_gfn(dp, gfn);
+        if ( !gfn_eq(gfn, INVALID_GFN) )
+            put_gfn(dp, gfn_x(gfn));
 
         addr += pagecnt;
         buf += pagecnt;
diff --git a/xen/arch/x86/domain.c b/xen/arch/x86/domain.c
index bb59247..c8c7e2d 100644
--- a/xen/arch/x86/domain.c
+++ b/xen/arch/x86/domain.c
@@ -783,7 +783,7 @@ int arch_domain_soft_reset(struct domain *d)
      * gfn == INVALID_GFN indicates that the shared_info page was never mapped
      * to the domain's address space and there is nothing to replace.
      */
-    if ( gfn == INVALID_GFN )
+    if ( gfn == gfn_x(INVALID_GFN) )
         goto exit_put_page;
 
     if ( mfn_x(get_gfn_query(d, gfn, &p2mt)) != mfn )
diff --git a/xen/arch/x86/hvm/emulate.c b/xen/arch/x86/hvm/emulate.c
index 855af4d..c55ad7b 100644
--- a/xen/arch/x86/hvm/emulate.c
+++ b/xen/arch/x86/hvm/emulate.c
@@ -455,7 +455,7 @@ static int hvmemul_linear_to_phys(
             return rc;
         pfn = _paddr >> PAGE_SHIFT;
     }
-    else if ( (pfn = paging_gva_to_gfn(curr, addr, &pfec)) == INVALID_GFN )
+    else if ( (pfn = paging_gva_to_gfn(curr, addr, &pfec)) == gfn_x(INVALID_GFN) )
     {
         if ( pfec & (PFEC_page_paged | PFEC_page_shared) )
             return X86EMUL_RETRY;
@@ -472,7 +472,8 @@ static int hvmemul_linear_to_phys(
         npfn = paging_gva_to_gfn(curr, addr, &pfec);
 
         /* Is it contiguous with the preceding PFNs? If not then we're done. */
-        if ( (npfn == INVALID_GFN) || (npfn != (pfn + (reverse ? -i : i))) )
+        if ( (npfn == gfn_x(INVALID_GFN)) ||
+             (npfn != (pfn + (reverse ? -i : i))) )
         {
             if ( pfec & (PFEC_page_paged | PFEC_page_shared) )
                 return X86EMUL_RETRY;
@@ -480,7 +481,7 @@ static int hvmemul_linear_to_phys(
             if ( done == 0 )
             {
                 ASSERT(!reverse);
-                if ( npfn != INVALID_GFN )
+                if ( npfn != gfn_x(INVALID_GFN) )
                     return X86EMUL_UNHANDLEABLE;
                 hvm_inject_page_fault(pfec, addr & PAGE_MASK);
                 return X86EMUL_EXCEPTION;
diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
index 23757a4..daaee1d 100644
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -3037,7 +3037,7 @@ static enum hvm_copy_result __hvm_copy(
         if ( flags & HVMCOPY_virt )
         {
             gfn = paging_gva_to_gfn(curr, addr, &pfec);
-            if ( gfn == INVALID_GFN )
+            if ( gfn == gfn_x(INVALID_GFN) )
             {
                 if ( pfec & PFEC_page_paged )
                     return HVMCOPY_gfn_paged_out;
@@ -3152,7 +3152,7 @@ static enum hvm_copy_result __hvm_clear(paddr_t addr, int size)
         count = min_t(int, PAGE_SIZE - (addr & ~PAGE_MASK), todo);
 
         gfn = paging_gva_to_gfn(curr, addr, &pfec);
-        if ( gfn == INVALID_GFN )
+        if ( gfn == gfn_x(INVALID_GFN) )
         {
             if ( pfec & PFEC_page_paged )
                 return HVMCOPY_gfn_paged_out;
@@ -5296,7 +5296,7 @@ static int do_altp2m_op(
              a.u.enable_notify.vcpu_id != curr->vcpu_id )
             rc = -EINVAL;
 
-        if ( (gfn_x(vcpu_altp2m(curr).veinfo_gfn) != INVALID_GFN) ||
+        if ( !gfn_eq(vcpu_altp2m(curr).veinfo_gfn, INVALID_GFN) ||
              mfn_eq(get_gfn_query_unlocked(curr->domain,
                     a.u.enable_notify.gfn, &p2mt), INVALID_MFN) )
             return -EINVAL;
diff --git a/xen/arch/x86/hvm/ioreq.c b/xen/arch/x86/hvm/ioreq.c
index 7148ac4..d2245e2 100644
--- a/xen/arch/x86/hvm/ioreq.c
+++ b/xen/arch/x86/hvm/ioreq.c
@@ -204,7 +204,7 @@ static void hvm_free_ioreq_gmfn(struct domain *d, unsigned long gmfn)
 {
     unsigned int i = gmfn - d->arch.hvm_domain.ioreq_gmfn.base;
 
-    if ( gmfn != INVALID_GFN )
+    if ( gmfn != gfn_x(INVALID_GFN) )
         set_bit(i, &d->arch.hvm_domain.ioreq_gmfn.mask);
 }
 
@@ -420,7 +420,7 @@ static int hvm_ioreq_server_map_pages(struct hvm_ioreq_server *s,
     if ( rc )
         return rc;
 
-    if ( bufioreq_pfn != INVALID_GFN )
+    if ( bufioreq_pfn != gfn_x(INVALID_GFN) )
         rc = hvm_map_ioreq_page(s, 1, bufioreq_pfn);
 
     if ( rc )
@@ -434,8 +434,8 @@ static int hvm_ioreq_server_setup_pages(struct hvm_ioreq_server *s,
                                         bool_t handle_bufioreq)
 {
     struct domain *d = s->domain;
-    unsigned long ioreq_pfn = INVALID_GFN;
-    unsigned long bufioreq_pfn = INVALID_GFN;
+    unsigned long ioreq_pfn = gfn_x(INVALID_GFN);
+    unsigned long bufioreq_pfn = gfn_x(INVALID_GFN);
     int rc;
 
     if ( is_default )
diff --git a/xen/arch/x86/hvm/svm/nestedsvm.c b/xen/arch/x86/hvm/svm/nestedsvm.c
index 9d2ac09..f9b38ab 100644
--- a/xen/arch/x86/hvm/svm/nestedsvm.c
+++ b/xen/arch/x86/hvm/svm/nestedsvm.c
@@ -1200,7 +1200,7 @@ nsvm_hap_walk_L1_p2m(struct vcpu *v, paddr_t L2_gpa, paddr_t *L1_gpa,
     /* Walk the guest-supplied NPT table, just as if it were a pagetable */
     gfn = paging_ga_to_gfn_cr3(v, nested_cr3, L2_gpa, &pfec, page_order);
 
-    if ( gfn == INVALID_GFN )
+    if ( gfn == gfn_x(INVALID_GFN) )
         return NESTEDHVM_PAGEFAULT_INJECT;
 
     *L1_gpa = (gfn << PAGE_SHIFT) + (L2_gpa & ~PAGE_MASK);
diff --git a/xen/arch/x86/hvm/vmx/vmx.c b/xen/arch/x86/hvm/vmx/vmx.c
index e2d69d8..e00d8c2 100644
--- a/xen/arch/x86/hvm/vmx/vmx.c
+++ b/xen/arch/x86/hvm/vmx/vmx.c
@@ -2056,13 +2056,13 @@ static int vmx_vcpu_emulate_vmfunc(struct cpu_user_regs *regs)
 static bool_t vmx_vcpu_emulate_ve(struct vcpu *v)
 {
     bool_t rc = 0, writable;
-    unsigned long gfn = gfn_x(vcpu_altp2m(v).veinfo_gfn);
+    gfn_t gfn = vcpu_altp2m(v).veinfo_gfn;
     ve_info_t *veinfo;
 
-    if ( gfn == INVALID_GFN )
+    if ( gfn_eq(gfn, INVALID_GFN) )
         return 0;
 
-    veinfo = hvm_map_guest_frame_rw(gfn, 0, &writable);
+    veinfo = hvm_map_guest_frame_rw(gfn_x(gfn), 0, &writable);
     if ( !veinfo )
         return 0;
     if ( !writable || veinfo->semaphore != 0 )
diff --git a/xen/arch/x86/mm/altp2m.c b/xen/arch/x86/mm/altp2m.c
index 10605c8..930bdc2 100644
--- a/xen/arch/x86/mm/altp2m.c
+++ b/xen/arch/x86/mm/altp2m.c
@@ -26,7 +26,7 @@ altp2m_vcpu_reset(struct vcpu *v)
     struct altp2mvcpu *av = &vcpu_altp2m(v);
 
     av->p2midx = INVALID_ALTP2M;
-    av->veinfo_gfn = _gfn(INVALID_GFN);
+    av->veinfo_gfn = INVALID_GFN;
 }
 
 void
diff --git a/xen/arch/x86/mm/hap/guest_walk.c b/xen/arch/x86/mm/hap/guest_walk.c
index d2716f9..1b1a15d 100644
--- a/xen/arch/x86/mm/hap/guest_walk.c
+++ b/xen/arch/x86/mm/hap/guest_walk.c
@@ -70,14 +70,14 @@ unsigned long hap_p2m_ga_to_gfn(GUEST_PAGING_LEVELS)(
         if ( top_page )
             put_page(top_page);
         p2m_mem_paging_populate(p2m->domain, cr3 >> PAGE_SHIFT);
-        return INVALID_GFN;
+        return gfn_x(INVALID_GFN);
     }
     if ( p2m_is_shared(p2mt) )
     {
         pfec[0] = PFEC_page_shared;
         if ( top_page )
             put_page(top_page);
-        return INVALID_GFN;
+        return gfn_x(INVALID_GFN);
     }
     if ( !top_page )
     {
@@ -110,12 +110,12 @@ unsigned long hap_p2m_ga_to_gfn(GUEST_PAGING_LEVELS)(
             ASSERT(p2m_is_hostp2m(p2m));
             pfec[0] = PFEC_page_paged;
             p2m_mem_paging_populate(p2m->domain, gfn_x(gfn));
-            return INVALID_GFN;
+            return gfn_x(INVALID_GFN);
         }
         if ( p2m_is_shared(p2mt) )
         {
             pfec[0] = PFEC_page_shared;
-            return INVALID_GFN;
+            return gfn_x(INVALID_GFN);
         }
 
         if ( page_order )
@@ -147,7 +147,7 @@ unsigned long hap_p2m_ga_to_gfn(GUEST_PAGING_LEVELS)(
     if ( !hvm_nx_enabled(v) && !hvm_smep_enabled(v) )
         pfec[0] &= ~PFEC_insn_fetch;
 
-    return INVALID_GFN;
+    return gfn_x(INVALID_GFN);
 }
 
 
diff --git a/xen/arch/x86/mm/hap/nested_ept.c b/xen/arch/x86/mm/hap/nested_ept.c
index 94cf832..02b27b1 100644
--- a/xen/arch/x86/mm/hap/nested_ept.c
+++ b/xen/arch/x86/mm/hap/nested_ept.c
@@ -236,7 +236,7 @@ int nept_translate_l2ga(struct vcpu *v, paddr_t l2ga,
     ept_walk_t gw;
     rwx_acc &= EPTE_RWX_MASK;
 
-    *l1gfn = INVALID_GFN;
+    *l1gfn = gfn_x(INVALID_GFN);
 
     rc = nept_walk_tables(v, l2ga, &gw);
     switch ( rc )
diff --git a/xen/arch/x86/mm/p2m-pod.c b/xen/arch/x86/mm/p2m-pod.c
index f384589..149f529 100644
--- a/xen/arch/x86/mm/p2m-pod.c
+++ b/xen/arch/x86/mm/p2m-pod.c
@@ -1003,7 +1003,7 @@ static void pod_eager_reclaim(struct p2m_domain *p2m)
         unsigned int idx = (mrp->idx + i++) % ARRAY_SIZE(mrp->list);
         unsigned long gfn = mrp->list[idx];
 
-        if ( gfn != INVALID_GFN )
+        if ( gfn != gfn_x(INVALID_GFN) )
         {
             if ( gfn & POD_LAST_SUPERPAGE )
             {
@@ -1020,7 +1020,7 @@ static void pod_eager_reclaim(struct p2m_domain *p2m)
             else
                 p2m_pod_zero_check(p2m, &gfn, 1);
 
-            mrp->list[idx] = INVALID_GFN;
+            mrp->list[idx] = gfn_x(INVALID_GFN);
         }
 
     } while ( (p2m->pod.count == 0) && (i < ARRAY_SIZE(mrp->list)) );
@@ -1031,7 +1031,7 @@ static void pod_eager_record(struct p2m_domain *p2m,
 {
     struct pod_mrp_list *mrp = &p2m->pod.mrp;
 
-    ASSERT(gfn != INVALID_GFN);
+    ASSERT(gfn != gfn_x(INVALID_GFN));
 
     mrp->list[mrp->idx++] =
         gfn | (order == PAGE_ORDER_2M ? POD_LAST_SUPERPAGE : 0);
diff --git a/xen/arch/x86/mm/p2m.c b/xen/arch/x86/mm/p2m.c
index b93c8a2..ff0cce8 100644
--- a/xen/arch/x86/mm/p2m.c
+++ b/xen/arch/x86/mm/p2m.c
@@ -76,7 +76,7 @@ static int p2m_initialise(struct domain *d, struct p2m_domain *p2m)
     p2m->np2m_base = P2M_BASE_EADDR;
 
     for ( i = 0; i < ARRAY_SIZE(p2m->pod.mrp.list); ++i )
-        p2m->pod.mrp.list[i] = INVALID_GFN;
+        p2m->pod.mrp.list[i] = gfn_x(INVALID_GFN);
 
     if ( hap_enabled(d) && cpu_has_vmx )
         ret = ept_p2m_init(p2m);
@@ -1863,7 +1863,7 @@ long p2m_set_mem_access(struct domain *d, gfn_t gfn, uint32_t nr,
     }
 
     /* If request to set default access. */
-    if ( gfn_x(gfn) == INVALID_GFN )
+    if ( gfn_eq(gfn, INVALID_GFN) )
     {
         p2m->default_access = a;
         return 0;
@@ -1932,7 +1932,7 @@ int p2m_get_mem_access(struct domain *d, gfn_t gfn, xenmem_access_t *access)
     };
 
     /* If request to get default access. */
-    if ( gfn_x(gfn) == INVALID_GFN )
+    if ( gfn_eq(gfn, INVALID_GFN) )
     {
         *access = memaccess[p2m->default_access];
         return 0;
@@ -2113,8 +2113,8 @@ unsigned long paging_gva_to_gfn(struct vcpu *v,
         mode = paging_get_nestedmode(v);
         l2_gfn = mode->gva_to_gfn(v, p2m, va, pfec);
 
-        if ( l2_gfn == INVALID_GFN )
-            return INVALID_GFN;
+        if ( l2_gfn == gfn_x(INVALID_GFN) )
+            return gfn_x(INVALID_GFN);
 
         /* translate l2 guest gfn into l1 guest gfn */
         rv = nestedhap_walk_L1_p2m(v, l2_gfn, &l1_gfn, &l1_page_order, &l1_p2ma,
@@ -2123,7 +2123,7 @@ unsigned long paging_gva_to_gfn(struct vcpu *v,
                                    !!(*pfec & PFEC_insn_fetch));
 
         if ( rv != NESTEDHVM_PAGEFAULT_DONE )
-            return INVALID_GFN;
+            return gfn_x(INVALID_GFN);
 
         /*
          * Sanity check that l1_gfn can be used properly as a 4K mapping, even
@@ -2415,7 +2415,7 @@ static void p2m_init_altp2m_helper(struct domain *d, unsigned int i)
     struct p2m_domain *p2m = d->arch.altp2m_p2m[i];
     struct ept_data *ept;
 
-    p2m->min_remapped_gfn = INVALID_GFN;
+    p2m->min_remapped_gfn = gfn_x(INVALID_GFN);
     p2m->max_remapped_gfn = 0;
     ept = &p2m->ept;
     ept->asr = pagetable_get_pfn(p2m_get_pagetable(p2m));
@@ -2551,7 +2551,7 @@ int p2m_change_altp2m_gfn(struct domain *d, unsigned int idx,
 
     mfn = ap2m->get_entry(ap2m, gfn_x(old_gfn), &t, &a, 0, NULL, NULL);
 
-    if ( gfn_x(new_gfn) == INVALID_GFN )
+    if ( gfn_eq(new_gfn, INVALID_GFN) )
     {
         if ( mfn_valid(mfn) )
             p2m_remove_page(ap2m, gfn_x(old_gfn), mfn_x(mfn), PAGE_ORDER_4K);
@@ -2613,7 +2613,7 @@ static void p2m_reset_altp2m(struct p2m_domain *p2m)
     /* Uninit and reinit ept to force TLB shootdown */
     ept_p2m_uninit(p2m);
     ept_p2m_init(p2m);
-    p2m->min_remapped_gfn = INVALID_GFN;
+    p2m->min_remapped_gfn = gfn_x(INVALID_GFN);
     p2m->max_remapped_gfn = 0;
 }
 
diff --git a/xen/arch/x86/mm/shadow/common.c b/xen/arch/x86/mm/shadow/common.c
index 42927e4..c22362f 100644
--- a/xen/arch/x86/mm/shadow/common.c
+++ b/xen/arch/x86/mm/shadow/common.c
@@ -1707,7 +1707,7 @@ static mfn_t emulate_gva_to_mfn(struct vcpu *v, unsigned long vaddr,
 
     /* Translate the VA to a GFN. */
     gfn = paging_get_hostmode(v)->gva_to_gfn(v, NULL, vaddr, &pfec);
-    if ( gfn == INVALID_GFN )
+    if ( gfn == gfn_x(INVALID_GFN) )
     {
         if ( is_hvm_vcpu(v) )
             hvm_inject_page_fault(pfec, vaddr);
diff --git a/xen/arch/x86/mm/shadow/multi.c b/xen/arch/x86/mm/shadow/multi.c
index f892e2f..e54c8b7 100644
--- a/xen/arch/x86/mm/shadow/multi.c
+++ b/xen/arch/x86/mm/shadow/multi.c
@@ -3660,7 +3660,7 @@ sh_gva_to_gfn(struct vcpu *v, struct p2m_domain *p2m,
          */
         if ( is_hvm_vcpu(v) && !hvm_nx_enabled(v) && !hvm_smep_enabled(v) )
             pfec[0] &= ~PFEC_insn_fetch;
-        return INVALID_GFN;
+        return gfn_x(INVALID_GFN);
     }
     gfn = guest_walk_to_gfn(&gw);
 
diff --git a/xen/arch/x86/mm/shadow/private.h b/xen/arch/x86/mm/shadow/private.h
index c424ad6..824796f 100644
--- a/xen/arch/x86/mm/shadow/private.h
+++ b/xen/arch/x86/mm/shadow/private.h
@@ -796,7 +796,7 @@ static inline unsigned long vtlb_lookup(struct vcpu *v,
                                         unsigned long va, uint32_t pfec)
 {
     unsigned long page_number = va >> PAGE_SHIFT;
-    unsigned long frame_number = INVALID_GFN;
+    unsigned long frame_number = gfn_x(INVALID_GFN);
     int i = vtlb_hash(page_number);
 
     spin_lock(&v->arch.paging.vtlb_lock);
diff --git a/xen/drivers/passthrough/amd/iommu_map.c b/xen/drivers/passthrough/amd/iommu_map.c
index c758459..b8c0a48 100644
--- a/xen/drivers/passthrough/amd/iommu_map.c
+++ b/xen/drivers/passthrough/amd/iommu_map.c
@@ -555,7 +555,7 @@ static int update_paging_mode(struct domain *d, unsigned long gfn)
     unsigned long old_root_mfn;
     struct domain_iommu *hd = dom_iommu(d);
 
-    if ( gfn == INVALID_GFN )
+    if ( gfn == gfn_x(INVALID_GFN) )
         return -EADDRNOTAVAIL;
     ASSERT(!(gfn >> DEFAULT_DOMAIN_ADDRESS_WIDTH));
 
diff --git a/xen/drivers/passthrough/vtd/iommu.c b/xen/drivers/passthrough/vtd/iommu.c
index f010612..c322b9f 100644
--- a/xen/drivers/passthrough/vtd/iommu.c
+++ b/xen/drivers/passthrough/vtd/iommu.c
@@ -611,7 +611,7 @@ static int __must_check iommu_flush_iotlb(struct domain *d,
         if ( iommu_domid == -1 )
             continue;
 
-        if ( page_count != 1 || gfn == INVALID_GFN )
+        if ( page_count != 1 || gfn == gfn_x(INVALID_GFN) )
             rc = iommu_flush_iotlb_dsi(iommu, iommu_domid,
                                        0, flush_dev_iotlb);
         else
@@ -640,7 +640,7 @@ static int __must_check iommu_flush_iotlb_pages(struct domain *d,
 
 static int __must_check iommu_flush_iotlb_all(struct domain *d)
 {
-    return iommu_flush_iotlb(d, INVALID_GFN, 0, 0);
+    return iommu_flush_iotlb(d, gfn_x(INVALID_GFN), 0, 0);
 }
 
 /* clear one page's page table */
diff --git a/xen/drivers/passthrough/x86/iommu.c b/xen/drivers/passthrough/x86/iommu.c
index cd435d7..69cd6c5 100644
--- a/xen/drivers/passthrough/x86/iommu.c
+++ b/xen/drivers/passthrough/x86/iommu.c
@@ -61,7 +61,7 @@ int arch_iommu_populate_page_table(struct domain *d)
             unsigned long mfn = page_to_mfn(page);
             unsigned long gfn = mfn_to_gmfn(d, mfn);
 
-            if ( gfn != INVALID_GFN )
+            if ( gfn != gfn_x(INVALID_GFN) )
             {
                 ASSERT(!(gfn >> DEFAULT_DOMAIN_ADDRESS_WIDTH));
                 BUG_ON(SHARED_M2P(gfn));
diff --git a/xen/include/asm-x86/guest_pt.h b/xen/include/asm-x86/guest_pt.h
index a8d980c..79ed4ff 100644
--- a/xen/include/asm-x86/guest_pt.h
+++ b/xen/include/asm-x86/guest_pt.h
@@ -32,7 +32,7 @@
 #error GUEST_PAGING_LEVELS not defined
 #endif
 
-#define VALID_GFN(m) (m != INVALID_GFN)
+#define VALID_GFN(m) (m != gfn_x(INVALID_GFN))
 
 static inline int
 valid_gfn(gfn_t m)
@@ -251,7 +251,7 @@ static inline gfn_t
 guest_walk_to_gfn(walk_t *gw)
 {
     if ( !(guest_l1e_get_flags(gw->l1e) & _PAGE_PRESENT) )
-        return _gfn(INVALID_GFN);
+        return INVALID_GFN;
     return guest_l1e_get_gfn(gw->l1e);
 }
 
diff --git a/xen/include/asm-x86/p2m.h b/xen/include/asm-x86/p2m.h
index 4ab3574..194020e 100644
--- a/xen/include/asm-x86/p2m.h
+++ b/xen/include/asm-x86/p2m.h
@@ -324,7 +324,7 @@ struct p2m_domain {
 #define NR_POD_MRP_ENTRIES 32
 
 /* Encode ORDER_2M superpage in top bit of GFN */
-#define POD_LAST_SUPERPAGE (INVALID_GFN & ~(INVALID_GFN >> 1))
+#define POD_LAST_SUPERPAGE (gfn_x(INVALID_GFN) & ~(gfn_x(INVALID_GFN) >> 1))
 
             unsigned long list[NR_POD_MRP_ENTRIES];
             unsigned int idx;
diff --git a/xen/include/xen/mm.h b/xen/include/xen/mm.h
index 7f207ec..58bc0b8 100644
--- a/xen/include/xen/mm.h
+++ b/xen/include/xen/mm.h
@@ -84,7 +84,7 @@ static inline bool_t mfn_eq(mfn_t x, mfn_t y)
 
 TYPE_SAFE(unsigned long, gfn);
 #define PRI_gfn          "05lx"
-#define INVALID_GFN      (~0UL)
+#define INVALID_GFN      _gfn(~0UL)
 
 #ifndef gfn_t
 #define gfn_t /* Grep fodder: gfn_t, _gfn() and gfn_x() are defined above */
