1. A computer system comprising: a host operating system kernel running at a first logical level above a hardware level of the computer system, wherein no intervening level exists between the first logical level and the hardware level of the computer system; a physical memory; a physical hardware device operating at the hardware level of the computer system, a read-only address space mapped to the physical memory, the read-only address space shared by multiple fault-isolated processes; and multiple processors to collectively execute the processes, wherein each of the processes operates logically above the host operating system kernel and is configured to communicate with other processes and the hardware device using the read-only address space without issuing system calls to the host operating system kernel.