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