x86/percpu: Clean up percpu_stable_op()

Use __pcpu_size_call_return() to simplify this_cpu_read_stable().
Also remove __bad_percpu_size() which is now unused.

Signed-off-by: Brian Gerst <[e-mail]>
Signed-off-by: Nick Desaulniers <[e-mail]>
Signed-off-by: Thomas Gleixner <[e-mail]>
Tested-by: Nick Desaulniers <[e-mail]>
Tested-by: Sedat Dilek <[e-mail]>
Reviewed-by: Nick Desaulniers <[e-mail]>
Acked-by: Linus Torvalds <[e-mail]>
Acked-by: Peter Zijlstra (Intel) <[e-mail]>
Acked-by: Dennis Zhou <[e-mail]>
Link: https://lkml.kernel.org/r/[e-mail]

arch/x86/include/asm/percpu.h

···
 
 /* For arch-specific code, we can use direct single-insn ops (they
  * don't give an lvalue though). */
-extern void __bad_percpu_size(void);
 
 #define __pcpu_type_1 u8
 #define __pcpu_type_2 u16
···
 	(typeof(_var))(unsigned long) pfo_val__;			\
 })
 
-#define percpu_stable_op(op, var)			\
-({							\
-	typeof(var) pfo_ret__;				\
-	switch (sizeof(var)) {				\
-	case 1:						\
-		asm(op "b "__percpu_arg(P1)",%0"	\
-		    : "=q" (pfo_ret__)			\
-		    : "p" (&(var)));			\
-		break;					\
-	case 2:						\
-		asm(op "w "__percpu_arg(P1)",%0"	\
-		    : "=r" (pfo_ret__)			\
-		    : "p" (&(var)));			\
-		break;					\
-	case 4:						\
-		asm(op "l "__percpu_arg(P1)",%0"	\
-		    : "=r" (pfo_ret__)			\
-		    : "p" (&(var)));			\
-		break;					\
-	case 8:						\
-		asm(op "q "__percpu_arg(P1)",%0"	\
-		    : "=r" (pfo_ret__)			\
-		    : "p" (&(var)));			\
-		break;					\
-	default: __bad_percpu_size();			\
-	}						\
-	pfo_ret__;					\
+#define percpu_stable_op(size, op, _var)				\
+({									\
+	__pcpu_type_##size pfo_val__;					\
+	asm(__pcpu_op2_##size(op, __percpu_arg(P[var]), "%[val]")	\
+	    : [val] __pcpu_reg_##size("=", pfo_val__)			\
+	    : [var] "p" (&(_var)));					\
+	(typeof(_var))(unsigned long) pfo_val__;			\
 })
 
 /*
···
  * per-thread variables implemented as per-cpu variables and thus
  * stable for the duration of the respective task.
  */
-#define this_cpu_read_stable(var)	percpu_stable_op("mov", var)
+#define this_cpu_read_stable_1(pcp)	percpu_stable_op(1, "mov", pcp)
+#define this_cpu_read_stable_2(pcp)	percpu_stable_op(2, "mov", pcp)
+#define this_cpu_read_stable_4(pcp)	percpu_stable_op(4, "mov", pcp)
+#define this_cpu_read_stable_8(pcp)	percpu_stable_op(8, "mov", pcp)
+#define this_cpu_read_stable(pcp)	__pcpu_size_call_return(this_cpu_read_stable_, pcp)
 
 #define raw_cpu_read_1(pcp)		percpu_from_op(1, , "mov", pcp)
 #define raw_cpu_read_2(pcp)		percpu_from_op(2, , "mov", pcp)