Re: [PATCH 14/15] x86/percpu: Remove !CONFIG_X86_CX8 methods

[Uros Bizjak]

On 25. 04. 25 10:42, Ingo Molnar wrote:
> TODO: review the constraints.
>
> NOT-Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
> ---
>   arch/x86/include/asm/percpu.h | 6 ++----
>   1 file changed, 2 insertions(+), 4 deletions(-)
>
> diff --git a/arch/x86/include/asm/percpu.h b/arch/x86/include/asm/percpu.h
> index 5fe314a2e73e..275c76a031ee 100644
> --- a/arch/x86/include/asm/percpu.h
> +++ b/arch/x86/include/asm/percpu.h
> @@ -334,8 +334,7 @@ do {									\
>   	new__.var = _nval;						\
>   									\
>   	asm_inline qual (						\
> -		ALTERNATIVE("call this_cpu_cmpxchg8b_emu",		\
> -			    "cmpxchg8b " __percpu_arg([var]), X86_FEATURE_CX8) \
> +		"cmpxchg8b " __percpu_arg([var])			\
>   		: ALT_OUTPUT_SP([var] "+m" (__my_cpu_var(_var)),	\
>   				"+a" (old__.low), "+d" (old__.high))	\
>   		: "b" (new__.low), "c" (new__.high),			\

There is no need for asm_inline, ALT_OUTPUT_SP() macro and "S" input 
(that was used to force the compiler to put the memory argument into 
%esi register):

	asm qual ("cmpxchg8b " __percpu_arg([var])		\
		: "+m" (__my_cpu_var(_var)),			\
		  "+a" (old__.low), "+d" (old__.high)		\
		: "b" (new__.low), "c" (new__.high)		\
		: "memory");					\

> @@ -363,8 +362,7 @@ do {									\
>   	new__.var = _nval;						\
>   									\
>   	asm_inline qual (						\
> -		ALTERNATIVE("call this_cpu_cmpxchg8b_emu",		\
> -			    "cmpxchg8b " __percpu_arg([var]), X86_FEATURE_CX8) \
> +		"cmpxchg8b " __percpu_arg([var])			\
>   		CC_SET(z)						\
>   		: ALT_OUTPUT_SP(CC_OUT(z) (success),			\
>   				[var] "+m" (__my_cpu_var(_var)),	\

Same here:

	asm qual ("cmpxchg8b " __percpu_arg([var])		\
		CC_SET(z)					\
		: CC_OUT(z) (success),				\
		  [var] "+m" (__my_cpu_var(_var)),		\
		  "+a" (old__.low), "+d" (old__.high)		\
		: "b" (new__.low), "c" (new__.high)		\
		: "memory");					\

Please see the attached patch that implements the change.

Uros.diff --git a/arch/x86/include/asm/percpu.h b/arch/x86/include/asm/percpu.h
index b0d03b6c279b..64c2e715af63 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])			\
+		: "+m" (__my_cpu_var(_var)),				\
+		  "+a" (old__.low), "+d" (old__.high)			\
+		: "b" (new__.low), "c" (new__.high)			\
 		: "memory");						\
 									\
 	old__.var;							\
@@ -364,15 +361,12 @@ do {									\
 	old__.var = *_oval;						\
 	new__.var = _nval;						\
 									\
-	asm_inline qual (						\
-		ALTERNATIVE("call this_cpu_cmpxchg8b_emu",		\
-			    "cmpxchg8b " __percpu_arg([var]), X86_FEATURE_CX8) \
+	asm qual ("cmpxchg8b " __percpu_arg([var])			\
 		CC_SET(z)						\
-		: ALT_OUTPUT_SP(CC_OUT(z) (success),			\
-				[var] "+m" (__my_cpu_var(_var)),	\
-				"+a" (old__.low), "+d" (old__.high))	\
-		: "b" (new__.low), "c" (new__.high),			\
-		  "S" (&(_var))						\
+		: CC_OUT(z) (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;					\