KVM: arm64: Introduce a bad_trap() primitive for unexpected trap handling

In order to ease the debugging of NV, it is helpful to have the kernel
shout at you when an unexpected trap is handled. We already have this
in a couple of cases. Make this a more generic infrastructure that we
will make use of very shortly.

Reviewed-by: Oliver Upton <oliver.upton@linux.dev>
Signed-off-by: Marc Zyngier <maz@kernel.org>

Author: Marc Zyngier

arch/arm64/kvm/sys_regs.c

@@ -45,24 +45,31 @@ static u64 sys_reg_to_index(const struct sys_reg_desc *reg);
 static int set_id_reg(struct kvm_vcpu *vcpu, const struct sys_reg_desc *rd,
 		      u64 val);
 
-static bool read_from_write_only(struct kvm_vcpu *vcpu,
-				 struct sys_reg_params *params,
-				 const struct sys_reg_desc *r)
+static bool bad_trap(struct kvm_vcpu *vcpu,
+		     struct sys_reg_params *params,
+		     const struct sys_reg_desc *r,
+		     const char *msg)
 {
-	WARN_ONCE(1, "Unexpected sys_reg read to write-only register\n");
+	WARN_ONCE(1, "Unexpected %s\n", msg);
 	print_sys_reg_instr(params);
 	kvm_inject_undefined(vcpu);
 	return false;
 }
 
+static bool read_from_write_only(struct kvm_vcpu *vcpu,
+				 struct sys_reg_params *params,
+				 const struct sys_reg_desc *r)
+{
+	return bad_trap(vcpu, params, r,
+			"sys_reg read to write-only register");
+}
+
 static bool write_to_read_only(struct kvm_vcpu *vcpu,
 			       struct sys_reg_params *params,
 			       const struct sys_reg_desc *r)
 {
-	WARN_ONCE(1, "Unexpected sys_reg write to read-only register\n");
-	print_sys_reg_instr(params);
-	kvm_inject_undefined(vcpu);
-	return false;
+	return bad_trap(vcpu, params, r,
+			"sys_reg write to read-only register");
 }
 
 u64 vcpu_read_sys_reg(const struct kvm_vcpu *vcpu, int reg)