x86/mm/pae: Make pmd_t similar to pte_t

Instead of mucking about with at least 2 different ways of fudging
it, do the same thing we do for pte_t.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20221022114424.580310787%40infradead.org

1 files changed, 14 insertions, 28 deletions

diff --git a/arch/x86/include/asm/pgtable-3level.h b/arch/x86/include/asm/pgtable-3level.h
index 28421a887209..28556d22feb8 100644
--- a/arch/x86/include/asm/pgtable-3level.h
+++ b/arch/x86/include/asm/pgtable-3level.h
@@ -87,7 +87,7 @@ static inline pmd_t pmd_read_atomic(pmd_t *pmdp)
 		ret |= ((pmdval_t)*(tmp + 1)) << 32;
 	}
 
-	return (pmd_t) { ret };
+	return (pmd_t) { .pmd = ret };
 }
 
 static inline void native_set_pte_atomic(pte_t *ptep, pte_t pte)
@@ -121,12 +121,11 @@ static inline void native_pte_clear(struct mm_struct *mm, unsigned long addr,
 	ptep->pte_high = 0;
 }
 
-static inline void native_pmd_clear(pmd_t *pmd)
+static inline void native_pmd_clear(pmd_t *pmdp)
 {
-	u32 *tmp = (u32 *)pmd;
-	*tmp = 0;
+	pmdp->pmd_low = 0;
 	smp_wmb();
-	*(tmp + 1) = 0;
+	pmdp->pmd_high = 0;
 }
 
 static inline void native_pud_clear(pud_t *pudp)
@@ -162,25 +161,17 @@ 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
 
-union split_pmd {
-	struct {
-		u32 pmd_low;
-		u32 pmd_high;
-	};
-	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;
+	pmd_t res;
 
 	/* 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;
+	res.pmd_low = xchg(&pmdp->pmd_low, 0);
+	res.pmd_high = READ_ONCE(pmdp->pmd_high);
+	WRITE_ONCE(pmdp->pmd_high, 0);
 
-	return res.pmd;
+	return res;
 }
 #else
 #define native_pmdp_get_and_clear(xp) native_local_pmdp_get_and_clear(xp)
@@ -199,17 +190,12 @@ static inline pmd_t pmdp_establish(struct vm_area_struct *vma,
 	 * 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;
+		old.pmd_low = xchg(&pmdp->pmd_low, pmd.pmd_low);
+		old.pmd_high = READ_ONCE(pmdp->pmd_high);
+		WRITE_ONCE(pmdp->pmd_high, pmd.pmd_high);
+
+		return old;
 	}
 
 	do {