Attention

EWAOL development has moved to the SOAFEE Special Interest Group and is now hosted at https://gitlab.com/soafee/ewaol/meta-ewaol. For more details on SOAFEE, please see https://soafee.io/.
Note this documentation is only applicable to the EWAOL’s repo hosted here : https://gitlab.arm.com/ewaol/meta-ewaol.

Build System

An EWAOL build can be configured by setting the target platform via the MACHINE BitBake variable, the desired distribution image features via the DISTRO_FEATURES BitBake variable, and customizing those features via feature-specific modifiable variables.

This page first overviews EWAOL’s support for the kas build tool. Each available distribution image feature and each supported target platform is then defined together with their associated kas configuration files, followed by any other additional customization options. The process for building without kas is then briefly described.

kas Build Tool Support

The kas build tool enables automatic fetch and inclusion of layer sources, as well as parameter and feature specification for building target images. To enable this, kas configuration files in the YAML format are passed to the tool to provide the necessary definitions.

These kas configuration files are modular, where passing multiple files will result in an image produced with their combined configuration. Further, kas configuration files can extend other kas configuration files, thereby enabling specialized configurations that inherit common configurations.

The meta-ewaol-config/kas directory contains kas configuration files that support building images via kas for the EWAOL project, and fall into three ordered categories:

  • Architecture Configs

  • Build Modifier Configs

  • Target Platform Configs

To build an EWAOL distribution image via kas, it is required to provide one Architecture Config and one Target Platform Config, unless otherwise stated in their descriptions below. Additional Build Modifiers are optional, and depend on the target use-case. Currently, it is necessary that kas configuration files are provided in order: the Architecture Config is defined first, then additional build features via zero or more Build Modifier Configs, and finally the Target Platform Config.

The kas configuration files to enable builds for a supported target platform or to configure each EWAOL distribution image feature, are described in their relevant sections below: Target Platforms and Distribution Image Features, respectively. Example usage of these kas configuration files can be found in the Build section of the User Guide.

Note

If a kas configuration file does not set a particular build parameter, the parameter will take its default value.

Target Platforms

There are currently two supported target platforms (corresponding to the MACHINE BitBake variable), each with an associated kas configuration file, as follows.

N1SDP

  • Corresponding value for MACHINE variable: n1sdp.

  • Target Platform Config: meta-ewaol-config/kas/n1sdp.yml.

This supported target platform is the Neoverse N1 System Development Platform (N1SDP), implemented in the meta-arm-bsp Yocto BSP layer.

To enable this, the n1sdp.yml Target Platform Config includes common configuration from the meta-ewaol-config/kas/include/arm-machines.yml kas configuration file, which defines the BSPs, layers, and dependencies required when building for the n1sdp.

AVA

  • Corresponding value for MACHINE variable: ava.

  • Target Platform Config: meta-ewaol-config/kas/ava.yml.

This supported target platform is the AVA Developer Platform (AVA), implemented in the meta-adlink-ampere Yocto BSP layer.

Distribution Image Features

For a particular target platform, the available EWAOL distribution image features (corresponding to the contents of the DISTRO_FEATURES BitBake variable) are detailed in this section, along with any associated kas configuration files, and any associated customization options relevant for that feature.

EWAOL Architectures

EWAOL distribution images can be configured via kas using Architecture Configs. These include a set of common configuration from a base EWAOL kas configuration file:

  • meta-ewaol-config/kas/include/ewaol-base.yml

This kas configuration file defines the base EWAOL layer dependencies and their software sources, as well as additional build configuration variables. It also includes the meta-ewaol-config/kas/include/ewaol-release.yml kas configuration file, where the layers dependencies are pinned for any corresponding EWAOL release.

Baremetal Architecture

  • Corresponding value in DISTRO_FEATURES variable: ewaol-baremetal.

  • Architecture Config: meta-ewaol-config/kas/baremetal.yml.

    This EWAOL distribution image feature:

    • Enables the ewaol-baremetal-image build target, to build an EWAOL baremetal distribution image.

    • Is incompatible with the ewaol-virtualization distribution image feature.

    The Architecture Config for this distribution image feature automatically appends ewaol-baremetal to DISTRO_FEATURES and sets the sets the build target to ewaol-baremetal-image.

    To build EWAOL baremetal distribution image, provide the Baremetal Architecture Config to the kas build command. For example, to build an EWAOL baremetal distribution image for the N1SDP hardware target platform, run the following command:

    kas build meta-ewaol-config/kas/baremetal.yml:meta-ewaol-config/kas/n1sdp.yml
    

Virtualization Architecture

  • Corresponding value in DISTRO_FEATURES variable: ewaol-virtualization.

  • Architecture Config: meta-ewaol-config/kas/virtualization.yml.

    This EWAOL distribution image feature:

    • Enables the ewaol-virtualization-image build target, to build an EWAOL virtualization distribution image.

    • Includes the Xen hypervisor into the software stack.

    • Enables Xen specific configs required by kernel.

    • Includes all necessary packages and adjustments to the Control VM’s root filesystem to support management of Xen Guest VMs.

    • Uses BitBake Multiple Configuration Build.

    • Includes a single Guest VM based on the generic-arm64 MACHINE, by default.

    • Is incompatible with the ewaol-baremetal distribution image feature.

    The Architecture Config for this distribution image feature automatically appends ewaol-virtualization to DISTRO_FEATURES and sets the sets the build target to ewaol-virtualization-image.

    To build EWAOL virtualization distribution image, provide the Virtualization Architecture Config to the kas build command. For example, to build an EWAOL virtualization distribution image for the N1SDP hardware target platform, run the following command:

    kas build meta-ewaol-config/kas/virtualization.yml:meta-ewaol-config/kas/n1sdp.yml
    
Customization

Configurable build-time variables for the Guest VM are defined within the meta-ewaol-distro/conf/multiconfig/ewaol-guest-vm.conf file and the meta-ewaol-distro/conf/distro/include/ewaol-guest-vm.inc which it includes.

The following list shows the standard set of available variables for the Control VM and the single default Guest VM, together with the default values (where MB and KB refer to Megabytes and Kilobytes, respectively):

EWAOL_GUEST_VM_INSTANCES: "1"                      # Number of Guest VM instances
EWAOL_GUEST_VM1_NUMBER_OF_CPUS: "4"                # Number of CPUs for Guest VM1
EWAOL_GUEST_VM1_MEMORY_SIZE: "6144"                # Memory size for Guest VM1 (MB)
EWAOL_GUEST_VM1_ROOTFS_EXTRA_SPACE: ""             # Extra storage space for Guest VM1 (KB)
EWAOL_CONTROL_VM_MEMORY_SIZE: "2048"               # Memory size for Control VM (MB)
EWAOL_CONTROL_VM_ROOTFS_EXTRA_SPACE: "0"           # Extra storage space for Control VM (KB), added as additional space above the storage necessary to support all Guest VMs root filesystems

The variables may be set either within an included kas configuration file (see meta-ewaol-config/kas/virtualization.yml for example usage), the environment, or manually via, for example, local.conf. The EWAOL_*_ROOTFS_EXTRA_SPACE variables apply their values to the relevant IMAGE_ROOTFS_EXTRA_SPACE BitBake variable.

Adding Extra EWAOL Guest VM Instances

It is possible to deploy multiple EWAOL Guest VM instances on the virtualization distribution image, each one based on the same kernel and image recipe. The number of Guest VM instances built for and included on the virtualization distribution image can be set via the EWAOL_GUEST_VM_INSTANCES variable.

Guest VM instances can be independently configured via BitBake variables which reference the Guest VM’s integer instance index, from 1 to the value of EWAOL_GUEST_VM_INSTANCES, inclusive. For example, variables with a prefix EWAOL_GUEST_VM1_ apply to the first Guest VM, variables with a prefix EWAOL_GUEST_VM2_ apply to the second Guest VM, and so on. All Guest VM instances use the same default configuration, apart from the hostname, which is generated for each Guest VM by appending the instance index to the EWAOL_GUEST_VM_HOSTNAME BitBake variable. By default, the first Guest VM will have a hostname ewaol-guest-vm1, the second will have a hostname ewaol-guest-vm2, and so on. An example of configuring a second Guest VM instance using the kas tool is given in meta-ewaol-config/kas/include/second-guest-vm-parameters.yml, although these variables will only be used if EWAOL_GUEST_VM_INSTANCES is set to build two or more Guest VMs.

Configuring Guest VM PCI Device Passthrough

An EWAOL virtualization distribution image running on the AVA Developer Platform is capable of supporting Xen PCI passthrough, allowing Guest VMs to be assigned exclusive use of a single PCI device. This capability is not enabled by default, and requires the following Build Modifier Config:

  • Build Modifier Config: meta-ewaol-config/kas/xen_pci_passthrough.yml.

    This Build Modifier Config appends xen-pci-passthrough to MACHINE_FEATURES.

Note

Xen PCI device passthrough is currently only supported on the AVA Developer Platform.

With the capability enabled, it is then possible to assign a single PCI device to a Guest VM by configuring an additional environment variable, provided for the corresponding Guest VM. This environment variable and its default value when the Build Modifier Config is provided to enable Xen PCI passthrough support is as follows:

EWAOL_GUEST_VM1_PCI_PASSTHROUGH_DEVICE: "0000:01:00.0"         # PCI device ID to be assigned

As described in the previous section, this example environment variable customizes the first Guest VM only, but other Guest VMs may be configured similarly (if they have been defined).

By default, the Build Modifier Config assigns the first PCI ethernet network device (which has device ID 0000:01:00.0) for exclusive use by the first Guest VM.

Warning

The PCI device IDs configured for PCI passthrough are not validated as part of the EWAOL build system, and it is therefore the responsibility of the user to ensure that the device IDs are valid, and that multiple Guest VMs have not been assigned exclusive use of the same PCI device.

Other EWAOL Features

Developer Support

  • Corresponding value in DISTRO_FEATURES variable: ewaol-devel.

    This EWAOL distribution image feature:

    • Is default if not set with any other EWAOL-specific DISTRO_FEATURES.

    • Includes packages appropriate for development image builds, such as the debug-tweaks package, which sets an empty root password for simplified development access.

Run-Time Integration Tests

  • Corresponding value in DISTRO_FEATURES variable: ewaol-test.

  • Build Modifier Config: meta-ewaol-config/kas/tests.yml.

    This EWAOL distribution image feature:

    • Includes the EWAOL test suites provided to validate the image is running successfully with the expected EWAOL functionalities.

    The Build Modifier for this distribution image feature automatically includes the Yocto Package Test (ptest) framework in the image, configures the inclusion of meta-ewaol-tests as a Yocto layer source for the build, and appends the ewaol-test feature to DISTRO_FEATURES for the build.

    To include run-time integration tests on an EWAOL distribution image, provide the Build Modifier Config to the kas build command.

    For example, to include the tests on an EWAOL distribution image for the N1SDP hardware target platform, run the following commands depending on the target architecture:

    • Baremetal architecture for N1SDP:

      kas build meta-ewaol-config/kas/baremetal.yml:meta-ewaol-config/kas/tests.yml:meta-ewaol-config/kas/n1sdp.yml
      
    • Virtualization architecture for N1SDP:

      kas build meta-ewaol-config/kas/virtualization.yml:meta-ewaol-config/kas/tests.yml:meta-ewaol-config/kas/n1sdp.yml
      

    Each suite of run-time integration tests and specific customizable variables associated with each suite are detailed separately, at Run-Time Integration Tests.

Security Hardening

  • Corresponding value in DISTRO_FEATURES variable: ewaol-security.

  • Build Modifier Config: meta-ewaol-config/kas/security.yml.

    This EWAOL distribution image feature:

    • Configures user accounts, packages, remote access controls and other image features to provide extra security hardening for the EWAOL distribution image.

    To include extra security hardening on an EWAOL distribution image, provide the Build Modifier Config to the kas build command, which appends the ewaol-security feature to DISTRO_FEATURES for the build.

    For example, to include it on the EWAOL distribution image for the N1SDP hardware target platform, run the following commands depending on the target architecture:

    • Baremetal architecture for N1SDP:

      kas build meta-ewaol-config/kas/baremetal.yml:meta-ewaol-config/kas/security.yml:meta-ewaol-config/kas/n1sdp.yml
      
    • Virtualization architecture for N1SDP:

      kas build meta-ewaol-config/kas/virtualization.yml:meta-ewaol-config/kas/security.yml:meta-ewaol-config/kas/n1sdp.yml
      

    The security hardening is described in more detail at Security Hardening.

Software Development Kit (SDK)

  • Corresponding value in DISTRO_FEATURES variable: ewaol-sdk.

  • Build Modifier Config: meta-ewaol-config/kas/baremetal-sdk.yml and meta-ewaol-config/kas/virtualization-sdk.yml, for the baremetal architecture and virtualization architecture, respectively.

    This EWAOL distribution image feature:

    • Adds the EWAOL Software Development Kit (SDK) which includes packages and image features to support on-target software development activities.

    • Enables two additional SDK build targets, ewaol-baremetal-sdk-image and ewaol-virtualization-sdk-image, each only compatible with the corresponding architecture’s distribution image feature.

    The Build Modifier for this distribution image feature automatically appends ewaol-sdk to DISTRO_FEATURES, and sets the appropriate build target with the necessary configuration from the relevant Architecture Config included by default, meaning it is not necessary to explicitly supply an Architecture Config to the kas build tool if passing an SDK Build Modifier Config.

    To include the SDK on an EWAOL distribution image, provide the appropriate SDK Build Modifier Config to the kas build command.

    For example, to include the SDK on an EWAOL distribution image for the N1SDP hardware target platform, run the following commands depending on the target architecture:

    • Baremetal architecture for N1SDP:

      kas build meta-ewaol-config/kas/baremetal-sdk.yml:meta-ewaol-config/kas/n1sdp.yml
      
    • Virtualization architecture for N1SDP:

      kas build meta-ewaol-config/kas/virtualization-sdk.yml:meta-ewaol-config/kas/n1sdp.yml
      

    The SDK itself is described in more detail at Software Development Kit (SDK).

Additional Distribution Image Customizations

An additional set of customization options are available for EWAOL distribution images, which don’t fall under a distinct distribution image feature. These customizations are listed below, grouped by the customization target.

Filesystem Customization

Adding Extra Rootfs Space

The size of the root filesystem can be extended via the EWAOL_ROOTFS_EXTRA_SPACE BitBake variable, which defaults to 2000000 Kilobytes. The value of this variable is appended to the IMAGE_ROOTFS_EXTRA_SPACE BitBake variable.

For an EWAOL virtualization distribution image, additional variables are provided which apply to the different root filesystems as described in Virtualization Architecture Customization. By default, the Control VM’s rootfs size is increased at build-time to support the sum of all Guest VM rootfs sizes. The customizable EWAOL_CONTROL_VM_ROOTFS_EXTRA_SPACE variable therefore corresponds just to the space allocated for the Control VM rootfs, in addition to the size necessary to support the Guest VM(s). Increasing EWAOL_ROOTFS_EXTRA_SPACE when building an EWAOL virtualization distribution image increases both the Guest VM(s) and Control VM rootfs size, which means that increasing this variable will result in the Control VM rootfs size expanding by more than the set value.

Filesystem Compilation Tuning

The EWAOL filesystem by default uses the generic armv8a-crc tune for aarch64 based target platforms. This reduces build times by increasing the sstate-cache reused between different image types and target platforms. This optimization can be disabled by setting EWAOL_GENERIC_ARM64_FILESYSTEM to "0". The tune used when EWAOL_GENERIC_ARM64_FILESYSTEM is enabled can be changed by setting EWAOL_GENERIC_ARM64_DEFAULTTUNE, which configures the DEFAULTTUNE BitBake variable for the aarch64 based target platforms builds. See DEFAULTTUNE for more information.

In summary, the relevant variables and their default values are:

EWAOL_GENERIC_ARM64_FILESYSTEM: "1"             # Enable generic file system (1 or 0).
EWAOL_GENERIC_ARM64_DEFAULTTUNE: "armv8a-crc"   # Value of DEFAULTTUNE if generic file system enabled.

Their values can be set by passing them as environmental variables. For example, the optimization can be disabled using:

EWAOL_GENERIC_ARM64_FILESYSTEM="0" kas build meta-ewaol-config/kas/baremetal.yml:meta-ewaol-config/kas/n1sdp.yml

Manual BitBake Build Setup

In order to build an EWAOL distribution image without the kas build tool directly via BitBake, it is necessary to prepare a BitBake project as follows:

  • Configure dependent Yocto layers in bblayers.conf.

  • Configure the DISTRO as ewaol in local.conf.

  • Configure the image DISTRO_FEATURES, including the EWAOL Architecture (ewaol-baremetal or ewaol-virtualization), in local.conf.

Assuming correct environment configuration, the BitBake build can then be run for the desired image target corresponding to one of the following:

  • ewaol-baremetal-image

  • ewaol-baremetal-sdk-image

  • ewaol-virtualization-image

  • ewaol-virtualization-sdk-image

As the kas build configuration files within the meta-ewaol-config/kas/ directory define the recommended build settings for each feature. Any additional functionalities may therefore be enabled by reading these configuration files and manually inserting their changes into the BitBake build environment.