1. A method for supporting virtual machine live migration in a host channel adapter (HCA) comprising an HCA microprocessor and an HCA memory and connected to a network, said HCA installed in a host computer comprising a host microprocessor and a host memory and a virtual machine (VM) operating on said host computer, the method comprising: configuring the HCA to implement a virtual switch using said HCA microprocessor and HCA memory; configuring the HCA to implement a plurality of virtual host channel adapters (vHCAs) associated with the virtual switch wherein each of the plurality of vHCAs is assigned a local identifier (LID) and provides a virtual interface (VI) having a separate VI namespace; attaching a vHCA of said plurality of vHCAs to said VM operating on said host computer, wherein said vHCA provides a queue pair (QP) for communicating messages between said VM and a communication endpoint over said network, and wherein said QP is provided by the VI provided by said vHCA and uses the LID assigned to said vHCA as a communication attribute; and wherein said HCA and vHCA are configured such that upon migrating said VM from said host computer to another host computer, said vHCA remains attached to said VM and continues to use said assigned LID after migration, such that said queue pair (QP) which uses said LID as a communication attribute continues to provide for communication of messages between said VM and said communication endpoint over said network after migration of said VM to said another host computer.