Who is Vishnu deva according to Buddhism?

Some Buddhists refer to Vishnu as Vasavatti Māra Deva. Others say that Upulvan Deva is Vishnu, and some say **Varuna** Deva is Vishnu. So who exactly is Vishnu? Is he Māra or a Deva? In Hinduism, Vishnu is known as the one who holds the chakraudha (sudhssana chakra). Upulvan deva consider as protector of sri Lanka Buddhist people say sri Lankan misunderstood Vishnu as upulvan. Some say both are same deva. So who is Vishnu....