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

hansendc · Ingo Molnar · commit dcb32d9913b7 · 2016-07-13T09:43:25.000+02:00
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 <dave.hansen@linux.intel.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Andy Lutomirski <luto@kernel.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Brian Gerst <brgerst@gmail.com> Cc: Dave Hansen <dave@sr71.net> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Luis R. Rodriguez <mcgrof@suse.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Toshi Kani <toshi.kani@hp.com> Cc: dave.hansen@intel.com Cc: linux-mm@kvack.org Cc: mhocko@suse.com Link: http://lkml.kernel.org/r/20160708001915.813703D9@viggo.jf.intel.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
@@ -354,7 +354,7 @@ phys_pte_init(pte_t *pte_page, unsigned long addr, unsigned long end,
 		 * 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;
@@ -396,7 +396,7 @@ phys_pmd_init(pmd_t *pmd_page, unsigned long address, unsigned long end,
 			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);
@@ -470,7 +470,7 @@ phys_pud_init(pud_t *pud_page, unsigned long addr, unsigned long end,
 			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,
@@ -673,7 +673,7 @@ static void __meminit free_pte_table(pte_t *pte_start, pmd_t *pmd)
 
 	for (i = 0; i < PTRS_PER_PTE; i++) {
 		pte = pte_start + i;
-		if (pte_val(*pte))
+		if (!pte_none(*pte))
 			return;
 	}
 
@@ -691,7 +691,7 @@ static void __meminit free_pmd_table(pmd_t *pmd_start, pud_t *pud)
 
 	for (i = 0; i < PTRS_PER_PMD; i++) {
 		pmd = pmd_start + i;
-		if (pmd_val(*pmd))
+		if (!pmd_none(*pmd))
 			return;
 	}
 
@@ -710,7 +710,7 @@ static bool __meminit free_pud_table(pud_t *pud_start, pgd_t *pgd)
 
 	for (i = 0; i < PTRS_PER_PUD; i++) {
 		pud = pud_start + i;
-		if (pud_val(*pud))
+		if (!pud_none(*pud))
 			return false;
 	}
 
diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c
@@ -1185,7 +1185,7 @@ static int __change_page_attr(struct cpa_data *cpa, int primary)
 		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) {
diff --git a/arch/x86/mm/pgtable_32.c b/arch/x86/mm/pgtable_32.c
@@ -47,7 +47,7 @@ void set_pte_vaddr(unsigned long vaddr, pte_t pteval)
 		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);

Original file line number	Diff line number	Diff line change
`@@ -47,7 +47,7 @@ void set_pte_vaddr(unsigned long vaddr, pte_t pteval)`
`47`	`47`	`return;`
`48`	`48`	`}`
`49`	`49`	`pte = pte_offset_kernel(pmd, vaddr);`
`50`		`- if (pte_val(pteval))`
	`50`	`+ if (!pte_none(pteval))`
`51`	`51`	`set_pte_at(&init_mm, vaddr, pte, pteval);`
`52`	`52`	`else`
`53`	`53`	`pte_clear(&init_mm, vaddr, pte);`