[PATCH RESEND -tip] x86/percpu: Fix "multiple identical address spaces specified for type" clang warning

[Uros Bizjak]

The clang build with named address spaces enabled currently fails with:

error: multiple identical address spaces specified for type [-Werror,-Wduplicate-decl-specifier]

The warning is emitted when accessing const_pcpu_hot structure,
which is already declared in __seg_gs named address space.

Use specialized accessor for __raw_cpu_read_const() instead, avoiding
redeclaring __seg_gs named address space via __raw_cpu_read().

Signed-off-by: Uros Bizjak <ubizjak@xxxxxxxxx>
Acked-by: Nathan Chancellor <nathan@xxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
Cc: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>
Cc: Bill Wendling <morbo@xxxxxxxxxx>
Cc: Justin Stitt <justinstitt@xxxxxxxxxx>
---
 arch/x86/include/asm/percpu.h | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/percpu.h b/arch/x86/include/asm/percpu.h
index c55a79d5feae..aeea5c8a17de 100644
--- a/arch/x86/include/asm/percpu.h
+++ b/arch/x86/include/asm/percpu.h
@@ -160,7 +160,10 @@ do {									\
 	*(qual __my_cpu_type(pcp) *)__my_cpu_ptr(&(pcp)) = (val);	\
 } while (0)
 
-#define __raw_cpu_read_const(pcp)	__raw_cpu_read(, , pcp)
+#define __raw_cpu_read_const(pcp)					\
+({									\
+	*(typeof(pcp) *)(__force uintptr_t)(&(pcp));			\
+})
 
 #else /* !CONFIG_USE_X86_SEG_SUPPORT: */
 
-- 
2.45.2