linux-kernel - [PATCH 15/15 -v4] x86/percpu: Remove !CONFIG_X86

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Message-ID: <aT-zSpBwSIeQuevD@gmail.com>
Date: Mon, 15 Dec 2025 08:05:46 +0100
From: Ingo Molnar <mingo@...nel.org>
To: Uros Bizjak <ubizjak@...il.com>
Cc: linux-kernel@...r.kernel.org, "Ahmed S . Darwish" <darwi@...utronix.de>,
	Andrew Cooper <andrew.cooper3@...rix.com>,
	Ard Biesheuvel <ardb@...nel.org>, Arnd Bergmann <arnd@...nel.org>,
	Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	"H . Peter Anvin" <hpa@...or.com>,
	John Ogness <john.ogness@...utronix.de>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: [PATCH 15/15 -v4] x86/percpu: Remove !CONFIG_X86_CX8 methods


* Uros Bizjak <ubizjak@...il.com> wrote:

> CC_SET() and CC_OUT() macros have been removed in the meantime [1], so
> the last two lines should be changed to:
> 
>     : "=@ccz" (success),
> 
> [1] https://lore.kernel.org/lkml/20250907183420.48569-1-ubizjak@gmail.com/

Indeed, -v4 patch attached.

Thanks,

	Ingo

=============>
From: Uros Bizjak <ubizjak@...il.com>
Date: Sun, 14 Dec 2025 09:40:31 +0100
Subject: [PATCH] x86/percpu: Remove !CONFIG_X86_CX8 methods

Adjust the constraints to the non-alternatives asm() statement.

Signed-off-by: Uros Bizjak <ubizjak@...il.com>
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Acked-by: Dave Hansen <dave.hansen@...ux.intel.com>
Cc: "Ahmed S . Darwish" <darwi@...utronix.de>
Cc: Andrew Cooper <andrew.cooper3@...rix.com>
Cc: Ard Biesheuvel <ardb@...nel.org>
Cc: Arnd Bergmann <arnd@...nel.org>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Dave Hansen <dave.hansen@...ux.intel.com>
Cc: "H . Peter Anvin" <hpa@...or.com>
Cc: John Ogness <john.ogness@...utronix.de>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Link: https://lore.kernel.org/r/15696bb3-126b-ef71-f838-80e1e1c1b0aa@gmail.com
---
 arch/x86/include/asm/percpu.h | 24 +++++++++---------------
 1 file changed, 9 insertions(+), 15 deletions(-)

diff --git a/arch/x86/include/asm/percpu.h b/arch/x86/include/asm/percpu.h
index 725d0eff7acd..ee98abae8427 100644
--- a/arch/x86/include/asm/percpu.h
+++ b/arch/x86/include/asm/percpu.h
@@ -335,13 +335,10 @@ do {									\
 	old__.var = _oval;						\
 	new__.var = _nval;						\
 									\
-	asm_inline qual (						\
-		ALTERNATIVE("call this_cpu_cmpxchg8b_emu",		\
-			    "cmpxchg8b " __percpu_arg([var]), X86_FEATURE_CX8) \
-		: ALT_OUTPUT_SP([var] "+m" (__my_cpu_var(_var)),	\
-				"+a" (old__.low), "+d" (old__.high))	\
-		: "b" (new__.low), "c" (new__.high),			\
-		  "S" (&(_var))						\
+	asm qual ("cmpxchg8b " __percpu_arg([var])			\
+		: [var] "+m" (__my_cpu_var(_var)),			\
+		  "+a" (old__.low), "+d" (old__.high)			\
+		: "b" (new__.low), "c" (new__.high)			\
 		: "memory");						\
 									\
 	old__.var;							\
@@ -364,14 +361,11 @@ do {									\
 	old__.var = *_oval;						\
 	new__.var = _nval;						\
 									\
-	asm_inline qual (						\
-		ALTERNATIVE("call this_cpu_cmpxchg8b_emu",		\
-			    "cmpxchg8b " __percpu_arg([var]), X86_FEATURE_CX8) \
-		: ALT_OUTPUT_SP("=@ccz" (success),			\
-				[var] "+m" (__my_cpu_var(_var)),	\
-				"+a" (old__.low), "+d" (old__.high))	\
-		: "b" (new__.low), "c" (new__.high),			\
-		  "S" (&(_var))						\
+	asm qual ("cmpxchg8b " __percpu_arg([var])			\
+		: "=@ccz" (success),					\
+		  [var] "+m" (__my_cpu_var(_var)),			\
+		  "+a" (old__.low), "+d" (old__.high)			\
+		: "b" (new__.low), "c" (new__.high)			\
 		: "memory");						\
 	if (unlikely(!success))						\
 		*_oval = old__.var;					\