Controlling hardware across two or more simultaneously running operating systems

A computing device has two or more software stacks, each stack simultaneously running a different operating system. Only one enabled operating system at a time has control of hardware resources of the computing device. Each disabled operating system has its device drivers disabled. The drivers may be disabled by stopping device driver messages to devices at a firmware layer unassociated with any operating system. The drivers may be disabled by having their associated operating system dynamically unload them when the operating system is disabled. In some instances, the drivers may be modified to include a "stop" control that tells the driver to stop communicating with its associated device, and a "resume" control that tells the driver to resume communication. When an operating system is disabled, the operating system may send a "stop" message to its device drivers. Drivers associated with messages passed between operating systems may remain enabled.