Xen ARM with Virtualization Extensions/Vexpress
Preparing the board
- We recommend disabling the A7 cpus by editing the board.txt file under the SITE directory corresponding to your Cortex A15 daughterboard:
SCC: 0x018 0x00001FFF ;Reset control - (CA7s reset, CA15s running) - uncomment this to hold A7 cluster in
- With recent firmware (newer than boot monitor V5.1.9), the Versatile Express can use multiple ways to bring up secondary cpus. Xen only supports sys_flags bring up. To select this mode, you need to set the bit of SCC: 0x700 to 0. For instance:
** Before: SCC: 0x700 0x0032F003 ** After: SCC: 0x700 0x0032E003
Booting Xen and dom0
Booting wit U-boot
The current approach requires tftp but it can be easily modify to load the different images from the mmc.
Build and flash U-Boot
Theses steps will programme U-Boot into NOR flash.
1) Clone U-Boot from the official repository (tested with v2013.10-rc2 tag)
git clone git://git.denx.de/u-boot.git u-boot cd u-boot git checkout v2013.10-rc2
2) Build U-Boot for the versatile express
make ARCH=arm CROSS_COMPILE=arm-unknown-linux-gnueabi- vexpress_ca15_tc2
3) Copy u-boot.bin from the root of the repository to the SOFTWARE directory of the firmware disk, giving it the name uboot.bin
cp u-boot.bin /media/VEMSD/SOFTWARE/uboot.bin
The arm-unknown-linux-gnueabi compiler can be retrieved from kernel.org.
4) Add U-Boot image at the end of /media/VEMSD/SITE1/HBI0249A/images.txt
NOR4UPDATE: AUTO ;IMAGE UPDATE:NONE/AUTO/FORCE NOR4ADDRESS: 00000000 ;Image Flash Address NOR4FILE: \SOFTWARE\uboot.bin ;Image File Name - master initrd NOR4LOAD: 80800000 ;Image Load Address NOR4ENTRY: 80800000 ;Image Entry Point
The TOTALIMAGES: line in the file will also need updating to account for this extra image and the 'NOR4' lines added may need to have a different number to '4' if that is not the next in sequence.
5) If you want to let the board to automatically boot into U-Boot (and by extension Xen), then:
- Look for the name of the BOOTSCRIPT image in the file you edited in the previous step; this should be \SOFTWARE\booscr.txt.
- Edit this bootscript file to have the line:
flash run u-boot
Booting without U-Boot
This solution requires to modify the firmware configuration. The support will be removed soon because Xen will require all CPU to boot in hypervisor mode. We advice to the use the U-Boot solution (see above).
If you are trying to run Xen on a Versatile Express Cortex A15 machine, you might want to copy xen (the Xen binary output, xen.git/xen/xen) and the Linux Dom0 zImage to the SOFTWARE directory and add the two following stanzas to your images.txt file:
NOR3UPDATE: AUTO ;IMAGE UPDATE:NONE/AUTO/FORCE NOR3ADDRESS: 0c000000 ;Image Flash Address NOR3FILE: \SOFTWARE\Xen\xen ;Image File Name NOR3LOAD: 80200000 ;Image Load Address NOR3ENTRY: 80200000 ;Image Entry Point NOR4UPDATE: AUTO ;IMAGE UPDATE:NONE/AUTO/FORCE NOR4ADDRESS: 000c0000 ;Image Flash Address NOR4FILE: \SOFTWARE\Xen\zImage ;Image File Name NOR4LOAD: 80008000 ;Image Load Address NOR4ENTRY: 80008000 ;Image Entry Point
- Note that before commit 47d1a51 (xen: arm: make zImage the default target which we install) it was necessary to use xen.git/xen/xen.bin for NOR3FILE instead of xen.git/xen/xen.
- The address of the Dom0 kernel in Flash at the moment is not configurable, it is defined as KERNEL_FLASH_ADDRESS in Xen. On a Versatile Express machine this address can be determined by executing flash list images from the boot manager. You'll have to manually change it.