x86_64 add NX mask for PTE entry

From: "bibo,mao" <bibo.mao@intel.com>
Hi,
    If function change_page_attr_addr calls revert_page to revert
to original pte value, mk_pte_phys does not mask NX bit. If NX bit
is set on no NX hardware supported x86_64 machine, there is will
be RSVD type page fault and system will crash. This patch adds NX
mask bit for PTE entry.

Signed-off-by: bibo,mao <bibo.mao@intel.com>
Signed-off-by: Andi Kleen <ak@suse.de>

---
 include/asm-x86_64/pgtable.h |    1 +
 1 files changed, 1 insertion(+)

Index: linux/include/asm-x86_64/pgtable.h
===================================================================
--- linux.orig/include/asm-x86_64/pgtable.h
+++ linux/include/asm-x86_64/pgtable.h
@@ -366,6 +366,7 @@ static inline pte_t mk_pte_phys(unsigned
 { 
 	pte_t pte;
 	pte_val(pte) = physpage | pgprot_val(pgprot); 
+	pte_val(pte) &= __supported_pte_mask;
 	return pte; 
 }