Introduction to ACRN Configuration

ACRN configuration is designed for System Integrators / Tier 1s to customize ACRN to meet their own needs. It allows users to adapt ACRN to target boards as well as configure hypervisor capabilities and provision VMs.

ACRN configuration consists of the following key components.

  • Configuration data saved as XML files.

  • A configuration toolset that helps users to generate and edit configuration data. The toolset includes:

    • Board inspector: Collects board-specific information on target machines.

    • ACRN configurator: Enables you to edit configuration data via a web-based UI.

The following sections introduce the concepts and tools of ACRN configuration from the aspects below.

Types of Configurations

ACRN includes three types of configurations: board, scenario, and launch. The configuration data are saved in three XML files. The following sections briefly describe the objectives and main contents of each file.

Board Configuration File

The board configuration file stores hardware-specific information extracted from the target platform. Examples of information:

  • Capacity of hardware resources (such as processors and memory)

  • Platform power states

  • Available devices

  • BIOS versions

You need a board configuration file to create scenario configurations. The board configuration is scenario-neutral by nature. Thus, multiple scenario configurations can be based on the same board configuration.

You also need a board configuration file to build an ACRN hypervisor. The build process uses the file to build a hypervisor that can initialize and manage the platform at runtime.

Scenario Configuration File

The scenario configuration file defines a working scenario by configuring hypervisor capabilities and defining some VM attributes and resources. We call these settings “static” because they are used to build the hypervisor. You can specify the following information in a scenario configuration:

  • Hypervisor capabilities

    • Availability and settings of hypervisor features, such as debugging facilities, scheduling algorithm, inter-VM shared memory (ivshmem), and security features.

    • Hardware management capacity of the hypervisor, such as maximum PCI devices and maximum interrupt lines supported.

    • Memory consumption of the hypervisor, such as the entry point and stack size.

  • VM attributes and resources

    • VM attributes, such as VM names.

    • Maximum number of VMs supported.

    • Resources allocated to each VM, such as number of vCPUs, amount of guest memory, and pass-through devices.

    • User VM settings, such as boot protocol and VM OS kernel parameters.

    • Settings of virtual devices, such as virtual UARTs.

You need a scenario configuration file to build an ACRN hypervisor. The build process uses the file to build a hypervisor that can initialize its capabilities and set up the VMs at runtime.

The scenario configuration defines User VMs as follows:

  • For pre-launched User VMs, the scenario configuration defines all attributes and resources (these VMs have static configurations by nature). The VM attributes and resources are exactly the amount of resources allocated to them.

  • For post-launched User VMs, the scenario configuration defines only static attributes and resources. Other resources are under the control of the Service VM and can be dynamically allocated to these VMs via launch scripts.

Launch Configuration File for Launch Scripts

The launch configuration file applies only to scenarios that have post-launched User VMs. The file defines certain attributes and resources of the post-launched VMs specified in the scenario configuration file. We call these settings “dynamic” because they are used at runtime.

You need a launch configuration file to generate a launch script (shell script) for each post-launched User VM. The launch script invokes the Service VM’s Device Model acrn-dm to create the VM. Unlike board and scenario configurations used at build time or by ACRN hypervisor, launch configurations are used dynamically in the Service VM.

Using ACRN Configuration Toolset

The ACRN configuration toolset enables you to create and edit configuration data. The toolset consists of the following:

As introduced in Configuration and Development Overview, configuration takes place at Step 3: Generate a Board Configuration File and Step 4: Generate a Scenario Configuration File and Launch Scripts in the overall development process:

../_images/overview_flow.png

ACRN source also includes makefile targets to aid customization. See Hypervisor Makefile Options.

ACRN Configuration Data

The following sections explain the format of the board, scenario, and launch configuration files. Although we recommend using the ACRN configuration toolset to create these files, this reference may be useful for advanced usage and troubleshooting.

ACRN source code offers predefined XMLs, and the generic templates used for new boards and scenarios, in the misc/config_tools/data/ directory of the acrn-hypervisor repo.

Board XML Format

The board XML has an acrn-config root element and a board attribute:

<acrn-config board="BOARD">

The board attribute defines the board name and must match the board attribute in the scenario configuration file and the launch configuration file. The file name of the board configuration file (example: my_board.xml) doesn’t affect the board name.

Board XML files are input to the ACRN configurator tool and the build system, and are not intended for end users to modify.

Scenario XML Format

The scenario XML has an acrn-config root element as well as board and scenario attributes:

<acrn-config board="BOARD" scenario="SCENARIO">

The board attribute specifies the board name and must match the board attribute in the board configuration file.

The scenario attribute specifies the scenario name, followed by hypervisor and VM settings.

See Scenario Configuration Options for a full explanation of available scenario XML elements.

Launch XML Format

The launch XML has an acrn-config root element as well as board, scenario and uos_launcher attributes:

<acrn-config board="BOARD" scenario="SCENARIO" uos_launcher="UOS_NUMBER">

The board attribute specifies the board name and must match the board attribute in the board configuration file and the scenario configuration file.

The scenario attribute specifies the scenario name and must match the scenario attribute in the scenario configuration file.

The uos_launcher attribute specifies the number of post-launched User VMs in a scenario.

See Launch Configuration Options for a full explanation of available launch XML elements.