ImageBuilder

Booting Xen from U-Boot requires:

- loading all the required binaries, manually specifying the loading address for each of them making sure they don't overlap

 - Xen, Dom0 kernel, Dom0 ramdisk, device tree binary, any Dom0-less DomUs kernels, ramdisk and partial dtbs for passthrough

- adding relevant nodes to device tree

 - the Dom0 kernel and ramdisk loading addresses need to be specified in device tree under /chosen

See booting.txt as a reference.

The processing is complex and cumbersome. To automate this configuration steps you can use ImageBuilder:

https://gitlab.com/ViryaOS/imagebuilder

ImageBuilder can be invoked as a container for build automation, but its useful scripts can also be called manually. Specifically, *script/uboot-script-gen* to generate a U-Boot script that loads all the necessary binaries and automatically adds the required entries to device tree at boot time.

First write a config file, like the following:

MEMORY_START="0x0" MEMORY_END="0x80000000" UBOOT_DIR="uboot" DEVICE_TREE="board.dtb" XEN="xen-hypervisor" DOM0_KERNEL="Image-dom0" DOM0_RAMDISK="ramdisk-dom0.rootfs.cpio.gz" NUM_DOMUS=2 DOMU_KERNEL[0]="dom1/Image-domU" DOMU_RAMDISK[0]="dom1/ramdisk-domU" DOMU_PASSTHROUGH_DTB[0]="dom1/passthrough-domU.dtb" DOMU_KERNEL[1]="dom2/Image-domU" DOMU_RAMDISK[1]="dom2/ramdisk-domU2" UBOOT_SOURCE="boot.source" UBOOT_SCRIPT="boot.scr"

The fields are self explanatory but you can find more detailed information on the readme. Make sure to use raw binaries for Xen, all the kernels and rootfs's, not U-Boot binaries (do *not* use the output of mkimage).

Then you can call uboot-script-gen as follows:

$ export LOAD_CMD="tftpb" $ bash ./scripts/uboot-script-gen /path/to/config

to generate a U-Boot script named *boot.scr* that will load all your binaries automatically using tftp, you just need to load boot.scr and source it.

$ tftpb 0xC00000 boot.scr; source 0xC00000

The command used to load the binaries can be customized, for instance you can have uboot-script-gen generate a U-Boot script that loads binaries from an SD card changing LOAD_CMD to "load scsi 0:1":

$ export LOAD_CMD="load scsi 0:1" $ bash ./scripts/uboot-script-gen /path/to/config