Customize

This section describes the supported customization options for Arm Zena CSS builds and how to apply them using build environment variables. It focuses on the configuration points exposed by the build system and highlights important constraints to consider when deviating from the default settings.

Note

The use of custom-built configurations is not automatically validated.

Available build environment variables

The available build configuration options and the associated environment variables are as follows:

Warning

For the Zena-CSS FVP, the amount of RAM cannot exceed 4064MB. This is derived by taking the 4096MB total and deducting 32MB for OP-TEE. For the Virtualization architecture, this is split between Xen, Dom0, DomU1 and DomU2.

Table 5 Available Build Environment Variables
Property	Architecture	Variable	Default
Primary Compute RAM size	Baremetal	`BAREMETAL_IMAGE_MEM_SIZE`	`2016M`
Primary Compute rootfs partition extra size	Baremetal and Virtualization (Dom0 only)	`CASSINI_ROOTFS_EXTRA_SPACE`	`0` (fixed units of KB)
Extra arguments for UEFI capsule generation	Baremetal and Virtualization	`CAPSULE_EXTRA_ARGS`	`--capflag PersistAcrossReset`
Path to the private key file in PEM format for UEFI capsule generation and authentication	Baremetal and Virtualization	`CAPSULE_PRIV_KEY_FILE`	yocto/meta-zena-css-bsp/recipes-bsp/u-boot/files/fvp-rd-aspen/capsule_dev_priv_key.pem
Dom0 RAM size	Virtualization	`DOM0_MEMORY_SIZE`	`1024M`
DomU1 RAM size	Virtualization	`DOMU1_MEMORY_SIZE`	`1024` (fixed units of MB)
DomU2 RAM size	Virtualization	`DOMU2_MEMORY_SIZE`	`1024` (fixed units of MB)

Using build environment variables

The Reference Software Stack image offers customizations to build configurations via environment variables. To use these variables, when reproducing one of the Use cases using the reproduce instructions, follow these steps:

Export the relevant build environment variables.

As an example for the Baremetal architecture, to set the Primary Compute RAM size to 4064MB and rootfs partition extra size to 5GB, issue:
```
export BAREMETAL_IMAGE_MEM_SIZE=4064M
export CASSINI_ROOTFS_EXTRA_SPACE=5242880
```
As an example for the Virtualization architecture, to set the Primary Compute Dom0 RAM size to 992MB, the DomU1 RAM size to 1536MB, keep the DomU2 memory size at the 1024MB default and set the Dom0 rootfs partition extra size to 5GB, issue:
```
export DOM0_MEMORY_SIZE=992M
export DOMU1_MEMORY_SIZE=1536
export DOMU2_MEMORY_SIZE=1024
export CASSINI_ROOTFS_EXTRA_SPACE=5242880
```
From the kas menu, choose the appropriate options then choose Build.
Remember to unset the environment variables so future builds do not use them.