diff --git a/arch/x86/xen/p2m.c b/arch/x86/xen/p2m.c
index 57001443231e..9bb3d82ffec8 100644
--- a/arch/x86/xen/p2m.c
+++ b/arch/x86/xen/p2m.c
@@ -507,7 +507,7 @@ unsigned long get_phys_to_machine(unsigned long pfn)
 	unsigned topidx, mididx, idx;
 
 	if (unlikely(pfn >= MAX_P2M_PFN))
-		return INVALID_P2M_ENTRY;
+		return IDENTITY_FRAME(pfn);
 
 	topidx = p2m_top_index(pfn);
 	mididx = p2m_mid_index(pfn);
diff --git a/arch/x86/xen/setup.c b/arch/x86/xen/setup.c
index 2afe55e21d59..210426a26cc0 100644
--- a/arch/x86/xen/setup.c
+++ b/arch/x86/xen/setup.c
@@ -468,6 +468,15 @@ char * __init xen_memory_setup(void)
 			i++;
 	}
 
+	/*
+	 * Set the rest as identity mapped, in case PCI BARs are
+	 * located here.
+	 *
+	 * PFNs above MAX_P2M_PFN are considered identity mapped as
+	 * well.
+	 */
+	set_phys_range_identity(map[i-1].addr / PAGE_SIZE, ~0ul);
+
 	/*
 	 * In domU, the ISA region is normal, usable memory, but we
 	 * reserve ISA memory anyway because too many things poke