1 files changed, 8 insertions, 1 deletions

diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
index 3f1783a79a3c..27336dfcda8e 100644
--- a/arch/x86/xen/mmu.c
+++ b/arch/x86/xen/mmu.c
@@ -1432,6 +1432,10 @@ static pte_t __init mask_rw_pte(pte_t *ptep, pte_t pte)
  * Init-time set_pte while constructing initial pagetables, which
  * doesn't allow RO page table pages to be remapped RW.
  *
+ * If there is no MFN for this PFN then this page is initially
+ * ballooned out so clear the PTE (as in decrease_reservation() in
+ * drivers/xen/balloon.c).
+ *
  * Many of these PTE updates are done on unpinned and writable pages
  * and doing a hypercall for these is unnecessary and expensive.  At
  * this point it is not possible to tell if a page is pinned or not,
@@ -1440,7 +1444,10 @@ static pte_t __init mask_rw_pte(pte_t *ptep, pte_t pte)
  */
 static void __init xen_set_pte_init(pte_t *ptep, pte_t pte)
 {
-        pte = mask_rw_pte(ptep, pte);
+        if (pte_mfn(pte) != INVALID_P2M_ENTRY)
+                pte = mask_rw_pte(ptep, pte);
+        else
+                pte = __pte_ma(0);
 
         native_set_pte(ptep, pte);
 }