linux-kernel - [PATCH] powerpc/8xx: Reverse order entries are written by __set_pte

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Message-Id: <67c3b5d44edfec054234ea9b4d05fc4b4f7f8a0e.1664346554.git.christophe.leroy@csgroup.eu>
Date:   Wed, 28 Sep 2022 08:29:22 +0200
From:   Christophe Leroy <christophe.leroy@...roup.eu>
To:     Michael Ellerman <mpe@...erman.id.au>,
        Nicholas Piggin <npiggin@...il.com>
Cc:     Christophe Leroy <christophe.leroy@...roup.eu>,
        linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: [PATCH] powerpc/8xx: Reverse order entries are written by __set_pte_at()

At the time being, with 16k pages __set_pte_at() writes table entries
in reverse order:

 294:	91 49 00 0c 	stw     r10,12(r9)
 298:	91 49 00 08 	stw     r10,8(r9)
 29c:	91 49 00 04 	stw     r10,4(r9)
 2a0:	91 49 00 00 	stw     r10,0(r9)

Allthough there should be no impact at all as it stays in a single
cacheline, reverse the writing in a more natural order.

 288:	91 49 00 0c 	stw     r10,0(r9)
 28c:	91 49 00 08 	stw     r10,4(r9)
 290:	91 49 00 04 	stw     r10,8(r9)
 294:	91 49 00 00 	stw     r10,12(r9)

Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
---
 arch/powerpc/include/asm/nohash/pgtable.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/powerpc/include/asm/nohash/pgtable.h b/arch/powerpc/include/asm/nohash/pgtable.h
index 4fd73c7412d0..d2e39823af09 100644
--- a/arch/powerpc/include/asm/nohash/pgtable.h
+++ b/arch/powerpc/include/asm/nohash/pgtable.h
@@ -183,7 +183,7 @@ static inline void __set_pte_at(struct mm_struct *mm, unsigned long addr,
 	 * cases, and 32-bit non-hash with 32-bit PTEs.
 	 */
 #if defined(CONFIG_PPC_8xx) && defined(CONFIG_PPC_16K_PAGES)
-	ptep->pte = ptep->pte1 = ptep->pte2 = ptep->pte3 = pte_val(pte);
+	ptep->pte3 = ptep->pte2 = ptep->pte1 = ptep->pte = pte_val(pte);
 #else
 	*ptep = pte;
 #endif
-- 
2.37.1