xen: fix mismerge in masking pte flags

Looks like a mismerge/misapply dropped one of the cases of pte flag
masking for Xen.  Also, only mask the flags for present ptes.
Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

arch/x86/xen/mmu.c

@@ -241,8 +241,10 @@ unsigned long long xen_pgd_val(pgd_t pgd)
 
 pte_t xen_make_pte(unsigned long long pte)
 {
-	if (pte & 1)
+	if (pte & _PAGE_PRESENT) {
 		pte = phys_to_machine(XPADDR(pte)).maddr;
+		pte &= ~(_PAGE_PCD | _PAGE_PWT);
+	}
 
 	return (pte_t){ .pte = pte };
 }
@@ -288,10 +290,10 @@ unsigned long xen_pgd_val(pgd_t pgd)
 
 pte_t xen_make_pte(unsigned long 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 };
 }