x86/mm/pae: Use WRITE_ONCE()

Peter Zijlstra · hansendc · commit f7bcd4617de6 · 2022-12-15T10:37:27.000-08:00
Disallow write-tearing, that would be really unfortunate. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20221022114425.038102604%40infradead.org
diff --git a/arch/x86/include/asm/pgtable-3level.h b/arch/x86/include/asm/pgtable-3level.h
@@ -27,9 +27,9 @@
  */
 static inline void native_set_pte(pte_t *ptep, pte_t pte)
 {
-	ptep->pte_high = pte.pte_high;
+	WRITE_ONCE(ptep->pte_high, pte.pte_high);
 	smp_wmb();
-	ptep->pte_low = pte.pte_low;
+	WRITE_ONCE(ptep->pte_low, pte.pte_low);
 }
 
 static inline void native_set_pte_atomic(pte_t *ptep, pte_t pte)
@@ -58,16 +58,16 @@ static inline void native_set_pud(pud_t *pudp, pud_t pud)
 static inline void native_pte_clear(struct mm_struct *mm, unsigned long addr,
 				    pte_t *ptep)
 {
-	ptep->pte_low = 0;
+	WRITE_ONCE(ptep->pte_low, 0);
 	smp_wmb();
-	ptep->pte_high = 0;
+	WRITE_ONCE(ptep->pte_high, 0);
 }
 
 static inline void native_pmd_clear(pmd_t *pmdp)
 {
-	pmdp->pmd_low = 0;
+	WRITE_ONCE(pmdp->pmd_low, 0);
 	smp_wmb();
-	pmdp->pmd_high = 0;
+	WRITE_ONCE(pmdp->pmd_high, 0);
 }
 
 static inline void native_pud_clear(pud_t *pudp)

Original file line number	Diff line number	Diff line change
`@@ -27,9 +27,9 @@`
`27`	`27`	`*/`
`28`	`28`	`static inline void native_set_pte(pte_t *ptep, pte_t pte)`
`29`	`29`	`{`
`30`		`- ptep->pte_high = pte.pte_high;`
	`30`	`+ WRITE_ONCE(ptep->pte_high, pte.pte_high);`
`31`	`31`	`smp_wmb();`
`32`		`- ptep->pte_low = pte.pte_low;`
	`32`	`+ WRITE_ONCE(ptep->pte_low, pte.pte_low);`
`33`	`33`	`}`
`34`	`34`
`35`	`35`	`static inline void native_set_pte_atomic(pte_t *ptep, pte_t pte)`
`@@ -58,16 +58,16 @@ static inline void native_set_pud(pud_t *pudp, pud_t pud)`
`58`	`58`	`static inline void native_pte_clear(struct mm_struct *mm, unsigned long addr,`
`59`	`59`	`pte_t *ptep)`
`60`	`60`	`{`
`61`		`- ptep->pte_low = 0;`
	`61`	`+ WRITE_ONCE(ptep->pte_low, 0);`
`62`	`62`	`smp_wmb();`
`63`		`- ptep->pte_high = 0;`
	`63`	`+ WRITE_ONCE(ptep->pte_high, 0);`
`64`	`64`	`}`
`65`	`65`
`66`	`66`	`static inline void native_pmd_clear(pmd_t *pmdp)`
`67`	`67`	`{`
`68`		`- pmdp->pmd_low = 0;`
	`68`	`+ WRITE_ONCE(pmdp->pmd_low, 0);`
`69`	`69`	`smp_wmb();`
`70`		`- pmdp->pmd_high = 0;`
	`70`	`+ WRITE_ONCE(pmdp->pmd_high, 0);`
`71`	`71`	`}`
`72`	`72`
`73`	`73`	`static inline void native_pud_clear(pud_t *pudp)`