	Xvisor on Allwinner A20 board (or Sun7i) using SD Booting 

This section of readme explains how to build & run Xvisor on actual Allwinner
A20 boards (cubieboard2 for example) using SD booting feature of Sun7i SOC.

By default, Xvisor for Sun7i supports Vexpress-A15 guest so we will show 
how to run Basic Firmware on Vexpress-A15 guest. For more info refer,
<xvisor_source>/tests/arm32/vexpress-a15/basic/README.

As first step of SD booting on Sun7i SOC, we need to re-partition and program
a SD card (> 4GB card) with Uboot. For detailed info on preparing SD card for 
booting refer: https://github.com/linux-sunxi/u-boot-sunxi/wiki

However, to enable both Core on the Allwinner A20 you need a u-boot version
supporting PSCI. This is not part of sunxi ou u-boot default git tree so you
need to use https://github.com/jcdubois/u-boot as your git tree fro u-boot in
the above link.

Once we have SD card prepared for SD booting, we add 2 images to the data 
partition of SD card:
 1) U-Boot compatible Xvisor binary (uvmm.bin)
 2) DTB for Xvisor (sun7i-a20-cubieboard2.dtb)
 3) Disk image containing guest binaries (disk.img)

Following are steps to create these images and then boot Xvisor on Allwinner
A20:

  [1. Build environment]
  # export CROSS_COMPILE=arm-linux-gnueabi-

  [2. GoTo Xvisor source directory]
  # cd <xvisor_source_directory>

  [3. Initialize Xvisor submodules]
  # git submodule init
  # git submodule update
  (Note: This is required to be done only once in freshly cloned xvisor source)

  [4. Configure Xvisor with Generic-v7-ve default settings]
  # make ARCH=arm generic-v7-ve-defconfig

  [5. Build Xvisor and DTBs]
  # make

  [6. Make U-Boot compatible uvmm.bin for use with bootm command]
  # mkimage -A arm -O linux -T kernel -C none -a 0x40008000 -e 0x40008000 -n Xvisor -d build/vmm.bin build/uvmm.bin

  [7. Build Basic Firmware]
  # make -C tests/arm32/vexpress-a15/basic

  [8. Copy defconfig to Linux build directory]
  # cp tests/arm32/vexpress-a15/linux/linux-<linux_version>_defconfig <linux_build_directory>/.config

  [9. GoTo Linux source directory]
  # cd <linux_source_directory>

  [10. Configure Linux in build directory]
  # make O=<linux_build_directory> ARCH=arm oldconfig

  [11. Build Linux in build directory]
  # make O=<linux_build_directory> ARCH=arm Image dtbs

  [12. Create BusyBox RAMDISK to be used as RootFS for Linux kernel]
  (Note: For subsequent steps, we will assume that your RAMDISK is located at <busybox_rootfs_directory>/rootfs.img)
  (Note: Please refer tests/common/busybox/README.md for creating rootfs.img using BusyBox)

  [13. GoTo Xvisor source directory]
  # cd <xvisor_source_directory>

  [14. Create disk image for Xvisor with Guest Linux and Guest Basic Firmware]
  # mkdir -p ./build/disk/tmp
  # mkdir -p ./build/disk/system
  # cp -f ./docs/banner/roman.txt ./build/disk/system/banner.txt
  # cp -f ./docs/logo/xvisor_logo_name.ppm ./build/disk/system/logo.ppm
  # mkdir -p ./build/disk/images/arm32/vexpress-a15
  # ./build/tools/dtc/bin/dtc -I dts -O dtb -o ./build/disk/images/arm32/vexpress-a15x2.dtb ./tests/arm32/vexpress-a15/vexpress-a15x2.dts
  # cp -f ./build/tests/arm32/vexpress-a15/basic/firmware.bin ./build/disk/images/arm32/vexpress-a15/firmware.bin
  # cp -f ./tests/arm32/vexpress-a15/linux/nor_flash.list ./build/disk/images/arm32/vexpress-a15/nor_flash.list
  # cp -f ./tests/arm32/vexpress-a15/linux/cmdlist ./build/disk/images/arm32/vexpress-a15/cmdlist
  # cp -f <linux_build_directory>/arch/arm/boot/Image ./build/disk/images/arm32/vexpress-a15/Image
  # cp -f <linux_build_directory>/arch/arm/boot/dts/vexpress-v2p-ca15-tc1.dtb ./build/disk/images/arm32/vexpress-a15/vexpress-v2p-ca15-tc1.dtb
  # cp -f <busybox_rootfs_directory>/rootfs.img ./build/disk/images/arm32/rootfs.img
  # genext2fs -B 1024 -b 32768 -d ./build/disk ./build/disk.img
  OR
  [14. Create disk image for Xvisor with only Guest Basic Firmware]
  # mkdir -p ./build/disk/tmp
  # mkdir -p ./build/disk/system
  # cp -f ./docs/banner/roman.txt ./build/disk/system/banner.txt
  # cp -f ./docs/logo/xvisor_logo_name.ppm ./build/disk/system/logo.ppm
  # mkdir -p ./build/disk/images/arm32/vexpress-a15
  # ./build/tools/dtc/bin/dtc -I dts -O dtb -o ./build/disk/images/arm32/vexpress-a15x2.dtb ./tests/arm32/vexpress-a15/vexpress-a15x2.dts
  # cp -f ./build/tests/arm32/vexpress-a15/basic/firmware.bin ./build/disk/images/arm32/vexpress-a15/firmware.bin
  # cp -f ./tests/arm32/vexpress-a15/basic/nor_flash.list ./build/disk/images/arm32/vexpress-a15/nor_flash.list
  # genext2fs -B 1024 -b 32768 -d ./build/disk ./build/disk.img

  [15. Make U-boot compatible initrd for use with bootm command]
  # mkimage -A arm -O linux -T ramdisk -a 0x41000000 -n "Xvisor ramdisk" -d build/disk.img build/udisk.img

  [16. Unplug bootable SD card from the A20 board and plug it on your development machine]

  [17. Mount data partition (or partition 2) of SD card on your development machine]

  [18. Copy uvmm.bin, DTB, and disk.img to data partition of SD card]
  # cp -f build/uvmm.bin <path_to_mounted_data_partition_of_sd_card>
  # cp -f build/arch/arm/board/generic/dts/allwinner/sun7i-a20-cubieboard2.dtb <path_to_mounted_data_partition_of_sd_card>
  # cp -f build/udisk.img <path_to_mounted_data_partition_of_sd_card>

  [19. Unmount data partition (or partition 2) of SD card from your development machine]

  [20. Unplug SD card from your development machine and plug it back on A20 board]

  [21. Connect to serial port of A20 board using Putty or Minicom]

  [22. Power-up or Reset A20 board and press any key when U-Boot shows auto-boot count down]

  [23. Enable MMC interface from U-Boot command line]
  sun7i# mmc dev 0:0

  [24. Copy Xvisor from SD card to SDRAM]
  sun7i# ext4load mmc 0:2 0x40200000 uvmm.bin

  [25. Copy the Xvisor DTB from SD card to SDRAM]
  sun7i# ext4load mmc 0:2 0x40800000 sun7i-a20-cubieboard2.dtb

  [26. Copy disk image from SD card to SDRAM]
  sun7i# ext4load mmc 0:2 0x41000000 udisk.img

  [27. Jump into Xvisor after disabling MMU, interrupts, etc]
  sun7i# bootm 0x40200000 0x41000000 0x40800000

  (Note: If you want to "autoboot" then you need to create a boot.scr file
   on the root of the SD card. To do so edit a boot.cmd text file and add all
   the commmands you want to execute automatically. For example you can put
   the following commands in the "boot.cmd" file:
   mmc dev 0:0
   ext4load mmc 0:2 0x40200000 uvmm.bin
   ext4load mmc 0:2 0x40800000 sun7i-a20-cubieboard2.dtb
   ext4load mmc 0:2 0x41000000 udisk.img
   bootm 0x40200000 0x41000000 0x40800000
   Then you can create the boot.scr file wit the following command:
   # mkimage -C none -A arm -T script -d boot.cmd boot.scr
   Put the boot.scr file a the root of your SD card.)

  [28. Kick Guest0 for starting Basic Firmware]
  XVisor# guest kick guest0

  [29. Bind to virtual UART]
  XVisor# vserial bind guest0/uart0

  [30. Try few commands of Basic firmware or goto next step]
  [guest0/uart0] basic# hi
  [guest0/uart0] basic# hello
  [guest0/uart0] basic# help

  [31. Copy linux from NOR flash to RAM and start linux booting from RAM]
  [guest0/uart0] basic# autoexec
  (Note: "autoexec" is a short-cut command)
  (Note: The <xvisor_source_directory>/tests/arm32/vexpress-a15/linux/cmdlist
   file which we have added to guest NOR flash contains set of commands for booting
   linux from NOR flash)

  [32. Wait for Linux prompt to come-up and then try out some commands]
  [guest0/uart0] / # ls

  [33. Enter character seqence 'ESCAPE+x+q" return to Xvisor prompt]
  [guest0/uart0] / #

  (Note: replace all <> brackets based on your workspace)
  (Note: some of the above steps will need to be adapted for other
   types of ARM host)
  (Note: for more info on your desired ARM host refer docs/arm/)
  (Note: you are free to change the ordering of above steps based
   on your workspace)
