Linux on the System/390

This paper is meant to serve as a general overview of the Linux port to the IBM System/390 mainframe architecture. The System/390 architecture is introduced, and its history and design are briefly discussed, including IBM's operating system VM, which allows virtualization of the System/390 and hence a way to split the machine into a large number of virtual machines. The short history of Linux on the platform is then covered, and ways in which running Linux on the System/390 make sense are discussed, chief among them the possibility of running many Linux instances on a single System/390.

Differences between the System/390 port and other ports of Linux are introduced, and the necessity for a general solution to the problem of timer interrupts in a virtual environment is raised. The I/O model of the System/390 is then described, with an example comparing a Linux/390 network driver with a PCI network driver that highlights some of the idiosyncracies of the System/390. Ways that a developer can begin working with Linux for System/390 are suggested, ranging from use of an employer's existing machine through acquisition of a used development machine to Hercules, a free System/390 emulator for Linux. Finally, areas in which development help is most badly needed are spotlighted.