Efficient incremental checkpointing of virtual devices

A virtualization platform provides fault tolerance for a primary virtual machine by continuously transmitting checkpoint information of the primary virtual machine to a collector process, such as a backup virtual machine. The virtualization platform includes virtual devices configured to keep track of state changes, for example, by using state flags or saving copies of prior state data. The virtualization platform generates incremental checkpoints by querying the virtual devices, which return state data based on whether the virtual devices have changed state since a prior checkpoint operation.