xen: mask unwanted pte bits in __supported_pte_mask

[ Stable: this isn't a bugfix in itself, but it's a pre-requiste
  for "xen: don't drop NX bit" ]

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Cc: Stable Kernel <stable@kernel.org>
Cc: the arch/x86 maintainers <x86@kernel.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
index 3525ef5..3f2a67f 100644
--- a/arch/x86/xen/mmu.c
+++ b/arch/x86/xen/mmu.c
@@ -199,10 +199,8 @@
 
 pte_t xen_make_pte(pteval_t pte)
 {
-	if (pte & _PAGE_PRESENT) {
+	if (pte & _PAGE_PRESENT)
 		pte = phys_to_machine(XPADDR(pte)).maddr;
-		pte &= ~(_PAGE_PCD | _PAGE_PWT);
-	}
 
 	return (pte_t){ .pte = pte };
 }