A system includes a virtualized I/O device coupled to one or more processing units. The virtualized I/O device includes programmed I/O (PIO) configuration registers corresponding to hardware resources, and a storage for storing a resource table that includes a plurality of entries. Each entry corresponds to a respective hardware resource. A system processor may allocate the hardware resources to functions that may include physical and virtual functions, and may program each entry of the resource discovery table for each function with an encoded value that indicates whether a requested hardware resource has been allocated to a requesting process, and whether the requested hardware resource is shared with another function. Processing units may execute a device driver instance associated with a given process to discover allocated resources by requesting access to the resource discovery table. The virtualized I/O device protects the resources by checking access requests against the resource discovery table.