1 files changed, 23 insertions, 0 deletions

diff --git a/arch/x86/include/asm/pgtable-3level.h b/arch/x86/include/asm/pgtable-3level.h
index 177b0165ea0..94b979d1b58 100644
--- a/arch/x86/include/asm/pgtable-3level.h
+++ b/arch/x86/include/asm/pgtable-3level.h
@@ -104,6 +104,29 @@ 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;
+                u32 pmd_high;
+        };
+        pmd_t pmd;
+};
+static inline pmd_t native_pmdp_get_and_clear(pmd_t *pmdp)
+{
+        union split_pmd res, *orig = (union split_pmd *)pmdp;
+
+        /* xchg acts as a barrier before setting of the high bits */
+        res.pmd_low = xchg(&orig->pmd_low, 0);
+        res.pmd_high = orig->pmd_high;
+        orig->pmd_high = 0;
+
+        return res.pmd;
+}
+#else
+#define native_pmdp_get_and_clear(xp) native_local_pmdp_get_and_clear(xp)
+#endif
+
 /*
  * Bits 0, 6 and 7 are taken in the low part of the pte,
  * put the 32 bits of offset into the high part.