acrn-hypervisor/doc/developer-guides/hld/hv-vm-management.rst
David B. Kinder 237997f3f9 doc: change UOS/SOS to User VM/Service VM
First pass at updating obsolete usage of "UOS" and "SOS"

Signed-off-by: David B. Kinder <david.b.kinder@intel.com>
2020-04-15 10:48:25 -07:00

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.. _hv-vm-management:
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.
:numref:`hvvm-state` illustrates the state-machine of a VM state transition,
please refer to :ref:`hv-cpu-virt` for related VCPU state.
.. figure:: images/hld-image108.png
:align: center
:name: hvvm-state
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.