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 <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
index bce2e5d..bb88fbc 100644 (file)
--- 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
index 7a1f7bb..7514215 100644 (file)
--- a/arch/x86/mm/pageattr.c
+++ b/arch/x86/mm/pageattr.c
@@ -1185,7 +1185,7 @@ repeat:
                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
index 75cc097..e67ae0e 100644 (file)
--- 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);