arm64: Add macro to compose a sysreg field value

A common idiom is to compose a tupple (reg, field, val) into
a symbol matching an autogenerated definition.

Add a help performing the concatenation and replace it when
open-coded implementations exist.

Suggested-by: Oliver Upton <oliver.upton@linux.dev>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Link: https://lore.kernel.org/r/20240122181344.258974-2-maz@kernel.org
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>

arch/arm64/include/asm/sysreg.h

@@ -1181,6 +1181,8 @@
 	par;								\
 })
 
+#define SYS_FIELD_VALUE(reg, field, val)	reg##_##field##_##val
+
 #define SYS_FIELD_GET(reg, field, val)		\
 		 FIELD_GET(reg##_##field##_MASK, val)
 
@@ -1188,7 +1190,8 @@
 		 FIELD_PREP(reg##_##field##_MASK, val)
 
 #define SYS_FIELD_PREP_ENUM(reg, field, val)		\
-		 FIELD_PREP(reg##_##field##_MASK, reg##_##field##_##val)
+		 FIELD_PREP(reg##_##field##_MASK,	\
+			    SYS_FIELD_VALUE(reg, field, val))
 
 #endif
 

arch/arm64/kvm/sys_regs.c

@@ -1685,7 +1685,8 @@ static u64 read_sanitised_id_aa64pfr0_el1(struct kvm_vcpu *vcpu,
 	u64 __f_val = FIELD_GET(reg##_##field##_MASK, val);		       \
 	(val) &= ~reg##_##field##_MASK;					       \
 	(val) |= FIELD_PREP(reg##_##field##_MASK,			       \
-			min(__f_val, (u64)reg##_##field##_##limit));	       \
+			    min(__f_val,				       \
+				(u64)SYS_FIELD_VALUE(reg, field, limit)));     \
 	(val);								       \
 })