| 1 | Virtual System Controller |
| 2 | ========================= |
| 3 | |
| 4 | The ``virt-ctrl`` device is a simple interface defined for the pure |
| 5 | virtual machine with no hardware reference implementation to allow the |
| 6 | guest kernel to send command to the host hypervisor. |
| 7 | |
| 8 | The specification can evolve, the current state is defined as below. |
| 9 | |
| 10 | This is a MMIO mapped device using 256 bytes. |
| 11 | |
| 12 | Two 32bit registers are defined: |
| 13 | |
| 14 | the features register (read-only, address 0x00) |
| 15 | This register allows the device to report features supported by the |
| 16 | controller. |
| 17 | The only feature supported for the moment is power control (0x01). |
| 18 | |
| 19 | the command register (write-only, address 0x04) |
| 20 | This register allows the kernel to send the commands to the hypervisor. |
| 21 | The implemented commands are part of the power control feature and |
| 22 | are reset (1), halt (2) and panic (3). |
| 23 | A basic command, no-op (0), is always present and can be used to test the |
| 24 | register access. This command has no effect. |