[PATCH 10/13] x86/mm/pae: Be consistent with pXXp_get_and_clear()

Peter Zijlstra
2022-10-22T11:48:53Z

Given that ptep_get_and_clear() uses cmpxchg8b, and that should be by
far the most common case, there's no point in having an optimized
variant for pmd/pud.

Introduce the pxx_xchg64() helper to implement the common logic once.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
arch/x86/include/asm/pgtable-3level.h | 67 ++++++++--------------------------
1 file changed, 17 insertions(+), 50 deletions(-)

--- a/arch/x86/include/asm/pgtable-3level.h
+++ b/arch/x86/include/asm/pgtable-3level.h
@@ -90,34 +90,33 @@ static inline void pud_clear(pud_t *pudp
*/
}

+
+#define pxx_xchg64(_pxx, _ptr, _val) ({ \
+ _pxx##val_t *_p = (_pxx##val_t *)_ptr; \
+ _pxx##val_t _o = *_p; \
+ do { } while (!try_cmpxchg64(_p, &_o, (_val))); \
+ native_make_##_pxx(_o); \
+})
+
#ifdef CONFIG_SMP
static inline pte_t native_ptep_get_and_clear(pte_t *ptep)
{
- pte_t old = *ptep;
-
- do {
- } while (!try_cmpxchg64(&ptep->pte, &old.pte, 0ULL));
-
- return old;
+ return pxx_xchg64(pte, ptep, 0ULL);
}
-#else
-#define native_ptep_get_and_clear(xp) native_local_ptep_get_and_clear(xp)
-#endif

-#ifdef CONFIG_SMP
static inline pmd_t native_pmdp_get_and_clear(pmd_t *pmdp)
{
- pmd_t res;
-
- /* xchg acts as a barrier before setting of the high bits */
- res.pmd_low = xchg(&pmdp->pmd_low, 0);
- res.pmd_high = READ_ONCE(pmdp->pmd_high);
- WRITE_ONCE(pmdp->pmd_high, 0);
+ return pxx_xchg64(pmd, pmdp, 0ULL);
+}

- return res;
+static inline pud_t native_pudp_get_and_clear(pud_t *pudp)
+{
+ return pxx_xchg64(pud, pudp, 0ULL);
}
#else
+#define native_ptep_get_and_clear(xp) native_local_ptep_get_and_clear(xp)
#define native_pmdp_get_and_clear(xp) native_local_pmdp_get_and_clear(xp)
+#define native_pudp_get_and_clear(xp) native_local_pudp_get_and_clear(xp)
#endif

#ifndef pmdp_establish
@@ -141,40 +140,8 @@ static inline pmd_t pmdp_establish(struc
return old;
}

- do {
- old = *pmdp;
- } while (cmpxchg64(&pmdp->pmd, old.pmd, pmd.pmd) != old.pmd);
-
- return old;
-}
-#endif
-
-#ifdef CONFIG_SMP
-union split_pud {
- struct {
- u32 pud_low;
- u32 pud_high;
- };
- pud_t pud;
-};
-
-static inline pud_t native_pudp_get_and_clear(pud_t *pudp)
-{
- union split_pud res, *orig = (union split_pud *)pudp;
-
-#ifdef CONFIG_PAGE_TABLE_ISOLATION
- pti_set_user_pgtbl(&pudp->p4d.pgd, __pgd(0));
-#endif
-
- /* xchg acts as a barrier before setting of the high bits */
- res.pud_low = xchg(&orig->pud_low, 0);
- res.pud_high = orig->pud_high;
- orig->pud_high = 0;
-
- return res.pud;
+ return pxx_xchg64(pmd, pmdp, pmd.pmd);
}
-#else
-#define native_pudp_get_and_clear(xp) native_local_pudp_get_and_clear(xp)
#endif

/* Encode and de-code a swap entry */