VM Management

The ACRN hypervisor maintained a dedicated VM structure instance for each running VM, and a series VM APIs like create_vm, start_vm, reset_vm, shutdown_vm etc are used to switch a VM to the right state, according to the requirements of applications or system power operations.

VM structure

The acrn_vm structure is defined to manage a VM instance, this structure maintained a VM’s HW resources like vcpu, vpic, vioapic, vuart, vpci. And at the same time acrn_vm structure also recorded a bunch of SW information related with corresponding VM, like info for VM identifier, info for SW loader, info for memory e820 entries, info for IO/MMIO handlers, info for platform level cpuid entries, and so on.

The acrn_vm structure instance will be created by create_vm API, and then work as the first parameter for other VM APIs.

VM state

Generally, a VM is not running at the beginning: it is in a ‘powered off’ state. After it got created successfully, the VM enter a ‘created’ state. Then the VM could be kick to run, and enter a ‘started’ state. When the VM powers off, the VM returns to a ‘powered off’ state again. A VM can be paused to wait some operation when it is running, so there is also a ‘paused’ state.

Figure 123 illustrates the state-machine of a VM state transition, please refer to CPU Virtualization for related VCPU state.

Figure 123 Hypervisor VM State Transition

VM State Management

Pre-launched and Service VM

The hypervisor is the owner to control pre-launched and Service VM’s state by calling VM APIs directly, and it follows the design of system power management. Please refer to ACRN power management design for more details.

Post-launched User VMs

DM is taking control of post-launched User VMs’ state transition after Service VM boot up, and it calls VM APIs through hypercalls.

Service VM user level service like Life-Cycle-Service and tool like Acrnd may work together with DM to launch or stop a User VM. Please refer to ACRN tool introduction for more details.