linux-kernel - [PATCH v2 09/10] x86/percpu: Clean up percpu_stable

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Date:   Sat, 30 May 2020 18:11:26 -0400
From:   Brian Gerst <brgerst@...il.com>
To:     linux-kernel@...r.kernel.org, x86@...nel.org
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>, Borislav Petkov <bp@...en8.de>,
        "H . Peter Anvin" <hpa@...or.com>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Brian Gerst <brgerst@...il.com>
Subject: [PATCH v2 09/10] 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 <brgerst@...il.com>
---
 arch/x86/include/asm/percpu.h | 41 ++++++++++-------------------------
 1 file changed, 12 insertions(+), 29 deletions(-)

diff --git a/arch/x86/include/asm/percpu.h b/arch/x86/include/asm/percpu.h
index 7efc0b5c4ff0..cf2b9c2a241e 100644
--- a/arch/x86/include/asm/percpu.h
+++ b/arch/x86/include/asm/percpu.h
@@ -85,7 +85,6 @@
 
 /* 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
@@ -167,33 +166,13 @@ do {									\
 	(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__;			\
 })
 
 /*
@@ -258,7 +237,11 @@ do {									\
  * 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)
-- 
2.25.4