linux-kernel - [PATCH v2] powerpc/32: Fix unpaired stwcx. on interrupt exit

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Message-ID: <6040b5dbcf5cdaa1cd919fcf0790f12974ea6e5a.1757666244.git.christophe.leroy@csgroup.eu>
Date: Fri, 12 Sep 2025 10:37:34 +0200
From: Christophe Leroy <christophe.leroy@...roup.eu>
To: Michael Ellerman <mpe@...erman.id.au>,
	Nicholas Piggin <npiggin@...il.com>,
	Madhavan Srinivasan <maddy@...ux.ibm.com>
Cc: Christophe Leroy <christophe.leroy@...roup.eu>,
	linux-kernel@...r.kernel.org,
	linuxppc-dev@...ts.ozlabs.org
Subject: [PATCH v2] powerpc/32: Fix unpaired stwcx. on interrupt exit

Commit b96bae3ae2cb ("powerpc/32: Replace ASM exception exit by C
exception exit from ppc64") erroneouly copied to powerpc/32 the logic
from powerpc/64 based on feature CPU_FTR_STCX_CHECKS_ADDRESS which is
always 0 on powerpc/32.

Re-instate the logic implemented by commit b64f87c16f3c ("[POWERPC]
Avoid unpaired stwcx. on some processors") which is based on
CPU_FTR_NEED_PAIRED_STWCX feature.

Fixes: b96bae3ae2cb ("powerpc/32: Replace ASM exception exit by C exception exit from ppc64")
Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
---
v2: Fixed the commit message (Wrong patch reference in the beginning)
---
 arch/powerpc/kernel/entry_32.S | 10 ++++------
 1 file changed, 4 insertions(+), 6 deletions(-)

diff --git a/arch/powerpc/kernel/entry_32.S b/arch/powerpc/kernel/entry_32.S
index 61ffd2989e7b..16f8ee6cb2cd 100644
--- a/arch/powerpc/kernel/entry_32.S
+++ b/arch/powerpc/kernel/entry_32.S
@@ -275,10 +275,9 @@ interrupt_return:
 	mtspr	SPRN_SRR1,r12
 
 BEGIN_FTR_SECTION
+	lwarx   r0,0,r1
+END_FTR_SECTION_IFSET(CPU_FTR_NEED_PAIRED_STWCX)
 	stwcx.	r0,0,r1		/* to clear the reservation */
-FTR_SECTION_ELSE
-	lwarx	r0,0,r1
-ALT_FTR_SECTION_END_IFCLR(CPU_FTR_STCX_CHECKS_ADDRESS)
 
 	lwz	r3,_CCR(r1)
 	lwz	r4,_LINK(r1)
@@ -319,10 +318,9 @@ ALT_FTR_SECTION_END_IFCLR(CPU_FTR_STCX_CHECKS_ADDRESS)
 	mtspr	SPRN_SRR1,r12
 
 BEGIN_FTR_SECTION
+	lwarx   r0,0,r1
+END_FTR_SECTION_IFSET(CPU_FTR_NEED_PAIRED_STWCX)
 	stwcx.	r0,0,r1		/* to clear the reservation */
-FTR_SECTION_ELSE
-	lwarx	r0,0,r1
-ALT_FTR_SECTION_END_IFCLR(CPU_FTR_STCX_CHECKS_ADDRESS)
 
 	lwz	r3,_LINK(r1)
 	lwz	r4,_CTR(r1)
-- 
2.49.0