Xen ARM with Virtualization Extensions/Arndale

The Arndale board is now supported in Xen upstream.
== Preparing the board ==
The bootloader provided with the Arndale does not let Xen boot in hypervisor mode, so we will use the u-boot provided by Linaro.
Follow the step on the Linaro wiki, to build and install u-boot.
== Building Xen and Linux Dom0 ==
First, we will build Linux for dom0 to have a device tree to provide to Xen.
You can get a tree from linaro which contains a working configuration for the Arndale.
 git clone -b linux-linaro git://git.linaro.org/kernel/linux-linaro-tracking.git linux
 cd linux
 ARCH=arm scripts/kconfig/merge_config.sh linaro/configs/linaro-base.conf linaro/configs/distribution.conf\
 linaro/configs/kvm-host.conf linaro/configs/xen.conf linaro/configs/arndale.conf linaro/configs/lt-arndale.conf
 make ARCH=arm zImage
 make ARCH=arm dtbs
The device tree used by the Arndale board is located in arch/arm/boot/dts/exynos5250-arndale.dtb
Then, Build Xen on ARM.
For the moment, xen doesn't build uImage for U-Boot. You can create the image with:
 mkimage -A arm -T kernel -a 0x80200000 -e 0x80200000 -C none -d "$xen_src/xen/xen" xen-uImage 
where $xen_src is the root directory of your xen git. Note that before commit 47d1a51 (xen: arm: make zImage the default target which we install) it was necessary to use $xen_src/xen/xen.bin instead.
== Booting Xen and Dom0 ==
To boot Xen and Dom0, you can use:
* PXE: it's easier for development but you need a computer which act as a server;
* copy binary on the SD card: when you don't have network on your board.
Once you have chosen the boot method, you can start to follow steps in the next sections.
When you have finished to configure your board, you can:
* Save the U-Boot configuration with saveenv command. The next time you want to reboot your board, you won't have to reconfigure U-Boot.
* Boot with boot command.
=== Booting via PXE ===
The following script allow U-boot to download everything via tftp and boot xen.
* Setup the PXE Server
* Copy xen-uImage, the zImage (rename in linux-zImage), exynos5250-arndale.dtb in /tftpboot/
* Copy the script in /tftpboot
 wget http://xenbits.xen.org/people/julieng/load-xen-tftp.scr.txt
 mkimage -T script -C none -d load-xen-tftp.scr.txt /tftpboot/load-xen-tftp.img
* At U-Boot prompt, on your board, you need to set the following variable:
 setenv ipaddr 10.y.y.y
 setenv serverip 10.x.x.x
 setenv usbethaddr 00:zz:zz:zz:zz:zz
 setenv ethaddr 00:zz:zz:zz:zz:zz
 setenv xen_addr_r 0x50000000
 setenv kernel_addr_r 0x60000000
 setenv dtb_addr_r 0x42000000
 setenv script_addr_r 0x40080000
 setenv xen_path /xen-uImage
 setenv kernel_path /linux-zImage
 setenv dtb_path /exynos5250-arndale.dtb
 setenv bootcmd 'tftpboot $script_addr_r /load-xen-tftp.img; source $script_addr_r'
 setenv xen_bootargs 'sync_console console=dtuart dtuart=/serial@12C20000'
 setenv dom0_bootargs 'console=hvc0 ignore_loglevel psci=enable clk_ignore_unused root=/dev/mmcblk1p3'
with:
* 10.y.y.y the ip addr of the board
* 10.x.x.x the ip of a tftp server (or PXE server).
* 00:zz:zz:zz:zz:zz the MAC address of the board. You can generate it with the following
** shell command:
 bash -c 'printf "00:16:3e:%02x:%02x:%02x\n" $(( $RANDOM % 256 )) $(( $RANDOM % 256 )) $(( $RANDOM % 256 ))'
** website: www.hellion.org.uk/cgi-bin/randmac.pl
=== Booting directly on the SD card ===
* Copy xen-uImage and the zImage the root directory of you SD card.
* At U-Boot prompt, on your board, you need to set the following variable:
 setenv kernel_addr_r 0x60000000
 setenv xen_addr_r 0x50000000
 setenv bootcmd_load_linux_mmc 'ext2load mmc 1:0 $kernel_addr_r /zImage'
 setenv boot_xen_mmc 'run bootcmd_load_linux_mmc; ext2load mmc 1:0 $xen_addr_r /xen-uImage; bootm $xen_addr_r -'
 setenv bootcmd 'run boot_xen_mmc'
We assume the SD card has only 1 partition with ext2 filesystem.
* execute the boot command with the following command:
 boot
====Alternate SD approach based on Linaro pre-built image for Arndale 5250====
On your host development machine, install [Linaro prebuilt] to a uSD card (assuming it mounts at /dev/sdb, see linaro instructions for more detail):
 $ wget https://releases.linaro.org/14.03/ubuntu/arndale/arndale-saucy_server_20140323-616.img.gz
 $ gunzip < arndale-saucy_server_20140323-616.img.gz | sudo dd bs=64k of=/dev/sdb
Copy your compiled xen-uImage, linux-zImage, and exynos5250-arndale.dtb all to the boot partition on the uSD card. Copy the contents of xen/dist/install to the rootfs partition. Unmount the uSD from your host development machine, insert it in the Arndale.
Start minicom on host development machine, connected to the Arndale via a serial cable:
 $ sudo minicom
Power on Arndale, press reset, watch the minicom console, and hit “enter” to interrupt U-Boot to get the u-Boot prompt. Enter the following into the minicom console. The saveenv stores the environment variables, so you won't have to repeat those the next time around.
 setenv xen_addr_r 0x50000000
 setenv kernel_addr_r 0x60000000
 setenv dtb_addr_r 0x42000000
 setenv xen_bootargs 'sync_console console=dtuart dtuart=/serial@12C20000 dom0_mem=512M'
 setenv dom0_bootargs 'console=hvc0 ignore_loglevel psci=enable clk_ignore_unused root=/dev/mmcblk1p3'
 saveenv
 fatload mmc 0:2 $kernel_addr_r linux-zImage
 fatload mmc 0:2 $xen_addr_r xen-uImage
 fatload mmc 0:2 $dtb_addr_r exynos5250-arndale.dtb
 fdt addr $dtb_addr_r
 fdt resize
 fdt set /chosen xen,xen-bootargs \"$xen_bootargs\"
 fdt set /chosen xen,dom0-bootargs \"$dom0_bootargs\"
 fdt mknode /chosen modules
 fdt set /chosen/modules '#address-cells' <1>
 fdt set /chosen/modules '#size-cells' <1> 
 fdt mknode /chosen/modules module@0 
 fdt set /chosen/modules/module@0 compatible xen,linux-zimage xen,multiboot-module 
 fdt set /chosen/modules/module@0 reg <$kernel_addr_r 0x00a00000> 
 bootm $xen_addr_r - $dtb_addr_r
== Resources ==
* Information about the Arndale board development: www.arndaleboard.org/wiki/index.php/WiKi.
* Linaro page about the Arndale board: wiki.linaro.org/Boards/Arndale/Setup/PXEBoot
* Alternate SD approach based on Linaro pre-built image (more detailed): Booting Linux in Xen's Dom0 on Arndale Exynos 5250
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