x86/mm: provide pmdp_establish() helper

[mirror_ubuntu-bionic-kernel.git] / arch / x86 / include / asm / pgtable-3level.h

diff --git a/arch/x86/include/asm/pgtable-3level.h b/arch/x86/include/asm/pgtable-3level.h
index a18fa4eac97bb64bb6c4ae86f380809d5395b908..a564084c6141d42f603b257160a34685e1bffdbe 100644 (file)
--- a/arch/x86/include/asm/pgtable-3level.h
+++ b/arch/x86/include/asm/pgtable-3level.h
@@ -161,7 +161,6 @@ static inline pte_t native_ptep_get_and_clear(pte_t *ptep)
 #define native_ptep_get_and_clear(xp) native_local_ptep_get_and_clear(xp)
 #endif
 
-#ifdef CONFIG_SMP
 union split_pmd {
        struct {
                u32 pmd_low;
@@ -169,6 +168,8 @@ union split_pmd {
        };
        pmd_t pmd;
 };
+
+#ifdef CONFIG_SMP
 static inline pmd_t native_pmdp_get_and_clear(pmd_t *pmdp)
 {
        union split_pmd res, *orig = (union split_pmd *)pmdp;
@@ -184,6 +185,40 @@ static inline pmd_t native_pmdp_get_and_clear(pmd_t *pmdp)
 #define native_pmdp_get_and_clear(xp) native_local_pmdp_get_and_clear(xp)
 #endif
 
+#ifndef pmdp_establish
+#define pmdp_establish pmdp_establish
+static inline pmd_t pmdp_establish(struct vm_area_struct *vma,
+               unsigned long address, pmd_t *pmdp, pmd_t pmd)
+{
+       pmd_t old;
+
+       /*
+        * If pmd has present bit cleared we can get away without expensive
+        * cmpxchg64: we can update pmdp half-by-half without racing with
+        * anybody.
+        */
+       if (!(pmd_val(pmd) & _PAGE_PRESENT)) {
+               union split_pmd old, new, *ptr;
+
+               ptr = (union split_pmd *)pmdp;
+
+               new.pmd = pmd;
+
+               /* xchg acts as a barrier before setting of the high bits */
+               old.pmd_low = xchg(&ptr->pmd_low, new.pmd_low);
+               old.pmd_high = ptr->pmd_high;
+               ptr->pmd_high = new.pmd_high;
+               return old.pmd;
+       }
+
+       do {
+               old = *pmdp;
+       } while (cmpxchg64(&pmdp->pmd, old.pmd, pmd.pmd) != old.pmd);
+
+       return old;
+}
+#endif
+
 #ifdef CONFIG_SMP
 union split_pud {
        struct {