diff --git a/xen/arch/arm/mm.c b/xen/arch/arm/mm.c
index 44258ad89c..e1cdeaaf2f 100644
--- a/xen/arch/arm/mm.c
+++ b/xen/arch/arm/mm.c
@@ -165,6 +165,7 @@ mfn_t xenheap_mfn_end __read_mostly;
 vaddr_t xenheap_virt_end __read_mostly;
 #ifdef CONFIG_ARM_64
 vaddr_t xenheap_virt_start __read_mostly;
+unsigned long xenheap_base_pdx __read_mostly;
 #endif
 
 unsigned long frametable_base_pdx __read_mostly;
@@ -796,6 +797,7 @@ void __init setup_xenheap_mappings(unsigned long base_mfn,
     if ( mfn_eq(xenheap_mfn_start, INVALID_MFN) )
     {
         xenheap_mfn_start = _mfn(base_mfn);
+        xenheap_base_pdx = mfn_to_pdx(_mfn(base_mfn));
         xenheap_virt_start = DIRECTMAP_VIRT_START +
             (base_mfn - mfn) * PAGE_SIZE;
     }
diff --git a/xen/include/asm-arm/mm.h b/xen/include/asm-arm/mm.h
index 3dbc8a6469..d6b5544015 100644
--- a/xen/include/asm-arm/mm.h
+++ b/xen/include/asm-arm/mm.h
@@ -135,6 +135,7 @@ extern mfn_t xenheap_mfn_start, xenheap_mfn_end;
 extern vaddr_t xenheap_virt_end;
 #ifdef CONFIG_ARM_64
 extern vaddr_t xenheap_virt_start;
+extern unsigned long xenheap_base_pdx;
 #endif
 
 #ifdef CONFIG_ARM_32
@@ -253,9 +254,10 @@ static inline void *maddr_to_virt(paddr_t ma)
 #else
 static inline void *maddr_to_virt(paddr_t ma)
 {
-    ASSERT(mfn_to_pdx(maddr_to_mfn(ma)) < (DIRECTMAP_SIZE >> PAGE_SHIFT));
+    ASSERT((mfn_to_pdx(maddr_to_mfn(ma)) - xenheap_base_pdx) <
+           (DIRECTMAP_SIZE >> PAGE_SHIFT));
     return (void *)(XENHEAP_VIRT_START -
-                    mfn_to_maddr(xenheap_mfn_start) +
+                    (xenheap_base_pdx << PAGE_SHIFT) +
                     ((ma & ma_va_bottom_mask) |
                      ((ma & ma_top_mask) >> pfn_pdx_hole_shift)));
 }