KVM: arm64: Make ID_REG_LIMIT_FIELD_ENUM() more widely available

ID_REG_LIMIT_FIELD_ENUM() is a useful macro to limit the idreg
features exposed to guest and userspace, and the NV code can
make use of it.

Signed-off-by: Marc Zyngier <maz@kernel.org>
Reviewed-by: Joey Gouly <joey.gouly@arm.com>
Link: https://lore.kernel.org/r/20250220134907.554085-8-maz@kernel.org
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>

Author: Marc Zyngier

arch/arm64/kvm/sys_regs.c

@@ -1803,16 +1803,6 @@ static u64 sanitise_id_aa64pfr0_el1(const struct kvm_vcpu *vcpu, u64 val)
 	return val;
 }
 
-#define ID_REG_LIMIT_FIELD_ENUM(val, reg, field, limit)			       \
-({									       \
-	u64 __f_val = FIELD_GET(reg##_##field##_MASK, val);		       \
-	(val) &= ~reg##_##field##_MASK;					       \
-	(val) |= FIELD_PREP(reg##_##field##_MASK,			       \
-			    min(__f_val,				       \
-				(u64)SYS_FIELD_VALUE(reg, field, limit)));     \
-	(val);								       \
-})
-
 static u64 sanitise_id_aa64dfr0_el1(const struct kvm_vcpu *vcpu, u64 val)
 {
 	val = ID_REG_LIMIT_FIELD_ENUM(val, ID_AA64DFR0_EL1, DebugVer, V8P8);

arch/arm64/kvm/sys_regs.h

@@ -247,4 +247,14 @@ int kvm_finalize_sys_regs(struct kvm_vcpu *vcpu);
 	CRn(sys_reg_CRn(reg)), CRm(sys_reg_CRm(reg)),	\
 	Op2(sys_reg_Op2(reg))
 
+#define ID_REG_LIMIT_FIELD_ENUM(val, reg, field, limit)			       \
+({									       \
+	u64 __f_val = FIELD_GET(reg##_##field##_MASK, val);		       \
+	(val) &= ~reg##_##field##_MASK;					       \
+	(val) |= FIELD_PREP(reg##_##field##_MASK,			       \
+			    min(__f_val,				       \
+				(u64)SYS_FIELD_VALUE(reg, field, limit)));     \
+	(val);								       \
+})
+
 #endif /* __ARM64_KVM_SYS_REGS_LOCAL_H__ */