KVM: VMX: Add a helper to test for a valid error code given an intr info

Add a helper, is_exception_with_error_code(), to provide the simple but
difficult to read code of checking for a valid exception with an error
code given a vmcs.VM_EXIT_INTR_INFO value.  The helper will gain another
user, vmx_get_exit_info(), in a future patch.
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Message-Id: <20200923201349.16097-4-sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/vmx/nested.c

@@ -5956,9 +5956,7 @@ bool nested_vmx_reflect_vmexit(struct kvm_vcpu *vcpu)
 	 * need to be synthesized by querying the in-kernel LAPIC, but external
 	 * interrupts are never reflected to L1 so it's a non-issue.
 	 */
-	if ((exit_intr_info &
-	     (INTR_INFO_VALID_MASK | INTR_INFO_DELIVER_CODE_MASK)) ==
-	    (INTR_INFO_VALID_MASK | INTR_INFO_DELIVER_CODE_MASK)) {
+	if (is_exception_with_error_code(exit_intr_info)) {
 		struct vmcs12 *vmcs12 = get_vmcs12(vcpu);
 
 		vmcs12->vm_exit_intr_error_code =

arch/x86/kvm/vmx/vmcs.h

@@ -138,6 +138,13 @@ static inline bool is_external_intr(u32 intr_info)
 	return is_intr_type(intr_info, INTR_TYPE_EXT_INTR);
 }
 
+static inline bool is_exception_with_error_code(u32 intr_info)
+{
+	const u32 mask = INTR_INFO_VALID_MASK | INTR_INFO_DELIVER_CODE_MASK;
+
+	return (intr_info & mask) == mask;
+}
+
 enum vmcs_field_width {
 	VMCS_FIELD_WIDTH_U16 = 0,
 	VMCS_FIELD_WIDTH_U64 = 1,