Method and apparatus for sharing a common routine stored in a single

Abstract

A computer system contains an Intel.TM. 80386 or later microprocessor as a central processing unit (CPU) and a system memory coupled to the CPU. The computer system runs Microsoft.TM. Windows v. 3.1 operating system in enhanced mode. The system memory contains a system virtual machine (VM) and at least one DOS VM. A target VM contains shared code routines for use by all VMs loaded in the computer system. When access to the shared code routine is desired from a calling process in a calling VM, the calling VM transfers control and calling data parameters to a shared code virtual device driver (VxD). The shared code VxD performs data translation for the calling data parameters so that the target VM can access the data parameters. The shared code VxD invokes calls to a Windows Process scheduler to schedule the target VM and block selection of the calling VM. The target VM, upon invocation by the scheduler, executes the shared code routine and generates return parameters. Upon completion of the shared code routine, the thread of execution is transferred to the shared code VxD, and address translation is performed on the return parameters. The translated return data parameters are transferred to the calling process. The shared code VxD unblocks selection of the calling VM so that the calling VM is free for selection by the Windows process scheduler. When the calling VM is selection, the calling processes resumes execution.