A method and apparatus are provided to perform live migration of a guest in a computer system using device assignment. In this method and apparatus, one or more pages of the guest are copied to a target computer system. It is determined which pages have been copied, and what incremental changes have been made to the pages that were copied. For example, the incremental changes may be indicated to a hypervisor of an initial host of the guest by a network interface controller or other device in the computer system. The incremental changes are then copied to the target computer system. Detection and copying of incremental changes may continue until a time when all dirty pages can be copied to the target computer system.