1Virtual System Controller 2========================= 3 4This device is a simple interface defined for the pure virtual machine with no 5hardware reference implementation to allow the guest kernel to send command 6to the host hypervisor. 7 8The specification can evolve, the current state is defined as below. 9 10This is a MMIO mapped device using 256 bytes. 11 12Two 32bit registers are defined: 13 141- the features register (read-only, address 0x00) 15 16 This register allows the device to report features supported by the 17 controller. 18 The only feature supported for the moment is power control (0x01). 19 202- the command register (write-only, address 0x04) 21 22 This register allows the kernel to send the commands to the hypervisor. 23 The implemented commands are part of the power control feature and 24 are reset (1), halt (2) and panic (3). 25 A basic command, no-op (0), is always present and can be used to test the 26 register access. This command has no effect. 27