x86/mm: Use pte_none() to test for empty PTE

The page table manipulation code seems to have grown a couple of
sites that are looking for empty PTEs. Just in case one of these
entries got a stray bit set, use pte_none() instead of checking
for a zero pte_val().

The use pte_same() makes me a bit nervous. If we were doing a
pte_same() check against two cleared entries and one of them had
a stray bit set, it might fail the pte_same() check. But, I
don't think we ever _do_ pte_same() for cleared entries. It is
almost entirely used for checking for races in fault-in paths.

Signed-off-by: Dave Hansen <[e-mail]>
Cc: Andrew Morton <[e-mail]>
Cc: Andy Lutomirski <[e-mail]>
Cc: Borislav Petkov <[e-mail]>
Cc: Brian Gerst <[e-mail]>
Cc: Dave Hansen <[e-mail]>
Cc: Denys Vlasenko <[e-mail]>
Cc: H. Peter Anvin <[e-mail]>
Cc: Josh Poimboeuf <[e-mail]>
Cc: Linus Torvalds <[e-mail]>
Cc: Luis R. Rodriguez <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Cc: Thomas Gleixner <[e-mail]>
Cc: Toshi Kani <[e-mail]>
Cc: [e-mail]
Cc: [e-mail]
Cc: [e-mail]
Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: Ingo Molnar <[e-mail]>

arch/x86/mm/init_64.c

···
 		 * pagetable pages as RO. So assume someone who pre-setup
 		 * these mappings are more intelligent.
 		 */
-		if (pte_val(*pte)) {
+		if (!pte_none(*pte)) {
 			if (!after_bootmem)
 				pages++;
 			continue;
···
 			continue;
 		}
 
-		if (pmd_val(*pmd)) {
+		if (!pmd_none(*pmd)) {
 			if (!pmd_large(*pmd)) {
 				spin_lock(&init_mm.page_table_lock);
 				pte = (pte_t *)pmd_page_vaddr(*pmd);
···
 			continue;
 		}
 
-		if (pud_val(*pud)) {
+		if (!pud_none(*pud)) {
 			if (!pud_large(*pud)) {
 				pmd = pmd_offset(pud, 0);
 				last_map_addr = phys_pmd_init(pmd, addr, end,
···
 
 	for (i = 0; i < PTRS_PER_PTE; i++) {
 		pte = pte_start + i;
-		if (pte_val(*pte))
+		if (!pte_none(*pte))
 			return;
 	}
 
···
 
 	for (i = 0; i < PTRS_PER_PMD; i++) {
 		pmd = pmd_start + i;
-		if (pmd_val(*pmd))
+		if (!pmd_none(*pmd))
 			return;
 	}
 
···
 
 	for (i = 0; i < PTRS_PER_PUD; i++) {
 		pud = pud_start + i;
-		if (pud_val(*pud))
+		if (!pud_none(*pud))
 			return false;
 	}
 

arch/x86/mm/pageattr.c

···
 		return __cpa_process_fault(cpa, address, primary);
 
 	old_pte = *kpte;
-	if (!pte_val(old_pte))
+	if (pte_none(old_pte))
 		return __cpa_process_fault(cpa, address, primary);
 
 	if (level == PG_LEVEL_4K) {

arch/x86/mm/pgtable_32.c

···
 		return;
 	}
 	pte = pte_offset_kernel(pmd, vaddr);
-	if (pte_val(pteval))
+	if (!pte_none(pteval))
 		set_pte_at(&init_mm, vaddr, pte, pteval);
 	else
 		pte_clear(&init_mm, vaddr, pte);