On 01/05/18 11:27, Ajay Garg wrote:
Hi All.
Hello,
I have been able to bring up xen on cubieboard2, using the following
script gathered from google :
###################################################################
# SUNXI Xen Boot Script
# Arch Linux ARM adaption of the cmd file which can be found at
http://openmirage.org/wiki/xen-on-cubieboard2
# Addresses suitable for 1GB system, adjust as appropriate for a 2GB system.
# Top of RAM: 0x80000000
# Xen relocate addr 0x7fe00000
setenv kernel_addr_r 0x7f600000 # 10 MB
setenv fdt_addr 0x7ec00000 # 2 MB
setenv xen_addr_r 0x7ea00000 # 2 MB
setenv fdt_high 0xffffffff # Load fdt in place instead of relocating
# Load xen/xen to ${xen_addr_r}.
fatload mmc 0 ${xen_addr_r} /xen
setenv bootargs "dom0_mem=256M"
# Load appropriate .dtb file to ${fdt_addr}
fatload mmc 0 ${fdt_addr} /sun7i-a20-cubieboard2.dtb
fdt addr ${fdt_addr} 0x40000
fdt resize
fdt chosen
fdt set /chosen \#address-cells <1>
fdt set /chosen \#size-cells <1>
# Load Linux arch/arm/boot/zImage to ${kernel_addr_r}
fatload mmc 0 ${kernel_addr_r} /zImage
fdt mknod /chosen module@0
fdt set /chosen/module@0 compatible "xen,linux-zimage" "xen,multiboot-module"
fdt set /chosen/module@0 reg <${kernel_addr_r} 0x${filesize} >
fdt set /chosen/module@0 bootargs "console=hvc0 rw root=/dev/mmcblk0p2
rootwait clk_ignore_unused"
bootz ${xen_addr_r} - ${fdt_addr}
###################################################################
I have been able to understand most of the workflow, except three things :
a)
Is the relocation-address of xen, given by
# Xen relocate addr 0x7fe00000
hardcoded? Or it is computed someway from ${kernel_addr_r},
{fdt_addr}, {xen_addr_r}?
In the bootup logs, xen does relocate to 0x7fe00000, so surely there
is some magic going ..
Xen will always relocate towards the end of the memory. See
get_xen_paddr() in xen/arch/arm/setup.c. As the placement of the
binaries by U-boot will have an impact to the relocation address, you
need to cleverly choose the different addresses.
b)
What does the argument 0x40000 signify in the following :
fdt addr ${fdt_addr} 0x40000
I consulted https://www.denx.de/wiki/DULG/UBootCmdFDT, but did not
find anything about this third argument.
It is explained in section 5.9.7.7. The length is optional and used to
tell the size of the FDT. This is useful in case the original FDT is not
big enough to create more properties/nodes.
c)
I assume filesize is the size of the kernel-binary, but how is it
determined in the following :
fdt set /chosen/module@0 reg <${kernel_addr_r} 0x${filesize} >
filesize will contain the size of the latest binary load in memory. The
udpate will be done by fatload command.
Cheers,
--
Julien Grall
_______________________________________________
U-Boot mailing list
U-Boot@lists.denx.de
https://lists.denx.de/listinfo/u-boot
