1. A method, comprising: reading, by a processor of a destination computer system, from a memory mapped into an address space of a virtual machine undergoing live migration from an origin computer system to the destination computer system, a data structure comprising a plurality of records, each record mapping an address of a memory page to an identifier of a virtual disk frame storing contents of the memory page, wherein the virtual disk frame is stored on a virtual disk that is employed by the virtual machine as a backing store for storing contents of memory pages, wherein the identifier of the virtual disk frame comprises an offset of the frame on the virtual disk, and wherein the virtual disk is accessible over a network by both the origin computer system and the destination computer system; reading, by the processor, from the memory mapped into the address space of the virtual machine, a plurality of page modification flags, each page modification flag indicating that contents of a corresponding memory page differ from contents of a virtual disk frame referenced by the data structure; and responsive to determining that a memory page is referenced by the data structure and that a page modification flag corresponding to the memory page is cleared, reading contents of the memory page from the virtual disk frame identified by the data structure.