diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
index 4c63b7f..b237167 100644
--- a/arch/x86/xen/mmu.c
+++ b/arch/x86/xen/mmu.c
@@ -195,7 +195,7 @@
  * 512 and 1024 entries respectively. 
  */
 
-static unsigned long max_p2m_pfn __read_mostly;
+unsigned long xen_max_p2m_pfn __read_mostly;
 
 #define P2M_PER_PAGE		(PAGE_SIZE / sizeof(unsigned long))
 #define P2M_MID_PER_PAGE	(PAGE_SIZE / sizeof(unsigned long *))
@@ -293,7 +293,7 @@
 		p2m_top_mfn_init(p2m_top_mfn);
 	}
 
-	for (pfn = 0; pfn < max_p2m_pfn; pfn += P2M_PER_PAGE) {
+	for (pfn = 0; pfn < xen_max_p2m_pfn; pfn += P2M_PER_PAGE) {
 		unsigned topidx = p2m_top_index(pfn);
 		unsigned mididx = p2m_mid_index(pfn);
 		unsigned long **mid;
@@ -335,7 +335,7 @@
 
 	HYPERVISOR_shared_info->arch.pfn_to_mfn_frame_list_list =
 		virt_to_mfn(p2m_top_mfn);
-	HYPERVISOR_shared_info->arch.max_pfn = max_p2m_pfn;
+	HYPERVISOR_shared_info->arch.max_pfn = xen_max_p2m_pfn;
 }
 
 /* Set up p2m_top to point to the domain-builder provided p2m pages */
@@ -345,7 +345,7 @@
 	unsigned long max_pfn = min(MAX_DOMAIN_PAGES, xen_start_info->nr_pages);
 	unsigned pfn;
 
-	max_p2m_pfn = max_pfn;
+	xen_max_p2m_pfn = max_pfn;
 
 	p2m_missing = extend_brk(PAGE_SIZE, PAGE_SIZE);
 	p2m_init(p2m_missing);
diff --git a/arch/x86/xen/setup.c b/arch/x86/xen/setup.c
index 6c9039e..cad2fcd 100644
--- a/arch/x86/xen/setup.c
+++ b/arch/x86/xen/setup.c
@@ -64,6 +64,8 @@
 		      "XEN EXTRA");
 
 	xen_extra_mem_size += size;
+
+	xen_max_p2m_pfn = PFN_DOWN(xen_extra_mem_start + xen_extra_mem_size);
 }
 
 static unsigned long __init xen_release_chunk(phys_addr_t start_addr,
diff --git a/arch/x86/xen/xen-ops.h b/arch/x86/xen/xen-ops.h
index 7c8ab86..d505e98 100644
--- a/arch/x86/xen/xen-ops.h
+++ b/arch/x86/xen/xen-ops.h
@@ -30,6 +30,7 @@
 pgd_t *xen_setup_kernel_pagetable(pgd_t *pgd, unsigned long max_pfn);
 void xen_ident_map_ISA(void);
 void xen_reserve_top(void);
+extern unsigned long xen_max_p2m_pfn;
 
 char * __init xen_memory_setup(void);
 void __init xen_arch_setup(void);