linux-kernel - [PATCH] powerpc/32s: Cleanup the mess in __set_pte

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Date:   Fri,  1 Jul 2022 08:24:20 +0200
From:   Christophe Leroy <christophe.leroy@...roup.eu>
To:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>
Cc:     Christophe Leroy <christophe.leroy@...roup.eu>,
        linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: [PATCH] powerpc/32s: Cleanup the mess in __set_pte_at()

__set_pte_at() handles 3 main cases with #ifdefs plus the 'percpu'
subcase which leads to code duplication.

Rewrite the function using IS_ENABLED() to minimise the total number
of cases and remove duplicated code.

Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
---
 arch/powerpc/include/asm/book3s/32/pgtable.h | 77 ++++++++------------
 1 file changed, 31 insertions(+), 46 deletions(-)

diff --git a/arch/powerpc/include/asm/book3s/32/pgtable.h b/arch/powerpc/include/asm/book3s/32/pgtable.h
index 40041ac713d9..2a0ca1f9a1ff 100644
--- a/arch/powerpc/include/asm/book3s/32/pgtable.h
+++ b/arch/powerpc/include/asm/book3s/32/pgtable.h
@@ -534,58 +534,43 @@ static inline pte_t pte_modify(pte_t pte, pgprot_t newprot)
 
 
 /* This low level function performs the actual PTE insertion
- * Setting the PTE depends on the MMU type and other factors. It's
- * an horrible mess that I'm not going to try to clean up now but
- * I'm keeping it in one place rather than spread around
+ * Setting the PTE depends on the MMU type and other factors.
+ *
+ * First case is 32-bit Hash MMU in SMP mode with 32-bit PTEs. We use the
+ * helper pte_update() which does an atomic update. We need to do that
+ * because a concurrent invalidation can clear _PAGE_HASHPTE. If it's a
+ * per-CPU PTE such as a kmap_atomic, we do a simple update preserving
+ * the hash bits instead (ie, same as the non-SMP case)
+ *
+ * Second case is 32-bit with 64-bit PTE.  In this case, we
+ * can just store as long as we do the two halves in the right order
+ * with a barrier in between. This is possible because we take care,
+ * in the hash code, to pre-invalidate if the PTE was already hashed,
+ * which synchronizes us with any concurrent invalidation.
+ * In the percpu case, we also fallback to the simple update preserving
+ * the hash bits
+ *
+ * Third case is 32-bit hash table in UP mode, we need to preserve
+ * the _PAGE_HASHPTE bit since we may not have invalidated the previous
+ * translation in the hash yet (done in a subsequent flush_tlb_xxx())
+ * and see we need to keep track that this PTE needs invalidating
  */
 static inline void __set_pte_at(struct mm_struct *mm, unsigned long addr,
 				pte_t *ptep, pte_t pte, int percpu)
 {
-#if defined(CONFIG_SMP) && !defined(CONFIG_PTE_64BIT)
-	/* First case is 32-bit Hash MMU in SMP mode with 32-bit PTEs. We use the
-	 * helper pte_update() which does an atomic update. We need to do that
-	 * because a concurrent invalidation can clear _PAGE_HASHPTE. If it's a
-	 * per-CPU PTE such as a kmap_atomic, we do a simple update preserving
-	 * the hash bits instead (ie, same as the non-SMP case)
-	 */
-	if (percpu)
-		*ptep = __pte((pte_val(*ptep) & _PAGE_HASHPTE)
-			      | (pte_val(pte) & ~_PAGE_HASHPTE));
-	else
-		pte_update(mm, addr, ptep, ~_PAGE_HASHPTE, pte_val(pte), 0);
+	if ((!IS_ENABLED(CONFIG_SMP) && !IS_ENABLED(CONFIG_PTE_64BIT)) || percpu) {
+		*ptep = __pte((pte_val(*ptep) & _PAGE_HASHPTE) |
+			      (pte_val(pte) & ~_PAGE_HASHPTE));
+	} else if (IS_ENABLED(CONFIG_PTE_64BIT)) {
+		if (pte_val(*ptep) & _PAGE_HASHPTE)
+			flush_hash_entry(mm, ptep, addr);
 
-#elif defined(CONFIG_PTE_64BIT)
-	/* Second case is 32-bit with 64-bit PTE.  In this case, we
-	 * can just store as long as we do the two halves in the right order
-	 * with a barrier in between. This is possible because we take care,
-	 * in the hash code, to pre-invalidate if the PTE was already hashed,
-	 * which synchronizes us with any concurrent invalidation.
-	 * In the percpu case, we also fallback to the simple update preserving
-	 * the hash bits
-	 */
-	if (percpu) {
-		*ptep = __pte((pte_val(*ptep) & _PAGE_HASHPTE)
-			      | (pte_val(pte) & ~_PAGE_HASHPTE));
-		return;
+		asm volatile("stw%X0 %2,%0; eieio; stw%X1 %L2,%1" :
+			     "=m" (*ptep), "=m" (*((unsigned char *)ptep+4)) :
+			     "r" (pte) : "memory");
+	} else {
+		pte_update(mm, addr, ptep, ~_PAGE_HASHPTE, pte_val(pte), 0);
 	}
-	if (pte_val(*ptep) & _PAGE_HASHPTE)
-		flush_hash_entry(mm, ptep, addr);
-	__asm__ __volatile__("\
-		stw%X0 %2,%0\n\
-		eieio\n\
-		stw%X1 %L2,%1"
-	: "=m" (*ptep), "=m" (*((unsigned char *)ptep+4))
-	: "r" (pte) : "memory");
-
-#else
-	/* Third case is 32-bit hash table in UP mode, we need to preserve
-	 * the _PAGE_HASHPTE bit since we may not have invalidated the previous
-	 * translation in the hash yet (done in a subsequent flush_tlb_xxx())
-	 * and see we need to keep track that this PTE needs invalidating
-	 */
-	*ptep = __pte((pte_val(*ptep) & _PAGE_HASHPTE)
-		      | (pte_val(pte) & ~_PAGE_HASHPTE));
-#endif
 }
 
 /*
-- 
2.36.1