Paravirtualization is an important I/O virtualization technology since it uniquely provides all of the following benefits: the ability to share the device between multiple VMs, support for legacy devices without virtualization hardware, and high performance. However, existing paravirtualization solutions have one main limitation: they only support one I/O device class, and would require significant engineering effort to support new device classes and features. In this paper, we present Paradice, a solution that vastly simplifies I/O paravirtualization by using a common paravirtualization boundary for various I/O device classes: Unix device files. Using this boundary, the paravirtual drivers simply act as a class-agnostic indirection layer between the application and the actual device driver.