linux-kernel - [PATCH -tip 4/5] x86/percpu: Introduce __raw_cpu_read

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Date: Tue, 30 Apr 2024 11:17:23 +0200
From: Uros Bizjak <ubizjak@...il.com>
To: x86@...nel.org,
	linux-kernel@...r.kernel.org
Cc: Uros Bizjak <ubizjak@...il.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...nel.org>,
	Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	"H. Peter Anvin" <hpa@...or.com>
Subject: [PATCH -tip 4/5] x86/percpu: Introduce __raw_cpu_read_const() macro

Introduce __raw_cpu_read_const() macro to further reduce ifdeffery
and differences between configs w/ and w/o USE_X86_SEG_SUPPORT.

No functional change intended.

Signed-off-by: Uros Bizjak <ubizjak@...il.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Ingo Molnar <mingo@...nel.org>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Dave Hansen <dave.hansen@...ux.intel.com>
Cc: "H. Peter Anvin" <hpa@...or.com>
---
 arch/x86/include/asm/percpu.h | 19 +++++++++----------
 1 file changed, 9 insertions(+), 10 deletions(-)

diff --git a/arch/x86/include/asm/percpu.h b/arch/x86/include/asm/percpu.h
index f360ac5fccde..d20255138426 100644
--- a/arch/x86/include/asm/percpu.h
+++ b/arch/x86/include/asm/percpu.h
@@ -156,6 +156,8 @@ do {									\
 	*(qual __my_cpu_type(pcp) *)__my_cpu_ptr(&(pcp)) = (val);	\
 } while (0)
 
+#define __raw_cpu_read_const(pcp)	__raw_cpu_read(, , pcp)
+
 #else /* CONFIG_USE_X86_SEG_SUPPORT */
 
 #define __raw_cpu_read(size, qual, _var)				\
@@ -180,6 +182,12 @@ do {									\
 	    : [val] __pcpu_reg_imm_##size(pto_val__));			\
 } while (0)
 
+/*
+ * The generic per-cpu infrastrucutre is not suitable for
+ * reading const-qualified variables.
+ */
+#define __raw_cpu_read_const(pcp)	({ BUILD_BUG(); (typeof(pcp))0; })
+
 #endif /* CONFIG_USE_X86_SEG_SUPPORT */
 
 #define percpu_stable_op(size, op, _var)				\
@@ -470,16 +478,7 @@ do {									\
 #define this_cpu_write_8(pcp, val)	__raw_cpu_write(8, volatile, pcp, val)
 #endif
 
-#ifdef CONFIG_USE_X86_SEG_SUPPORT
-#define this_cpu_read_const(pcp)	__raw_cpu_read(, , pcp)
-#else /* CONFIG_USE_X86_SEG_SUPPORT */
-
-/*
- * The generic per-cpu infrastrucutre is not suitable for
- * reading const-qualified variables.
- */
-#define this_cpu_read_const(pcp)	({ BUILD_BUG(); (typeof(pcp))0; })
-#endif /* CONFIG_USE_X86_SEG_SUPPORT */
+#define this_cpu_read_const(pcp)	__raw_cpu_read_const(pcp)
 
 #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)
-- 
2.44.0