On PowerNV systems, the rootfs is passed through kexec, which loads the rootfs
into memory and set two fdt entries to describe where the file is located in
I need to pass this memory region to the md device as a mfs_root, but, current
md driver does not support two things:
- Just getting a pointer from an external (bootloader) memory. If I need to workaround it, I would need to declare a static array and memcopy from this external memory to this static variable.
- The size of the image. The usage of mfs_root_end, which is not a pointer, seems to be not possible for this prestaged scenario.
This patch simply adds a new way to load mfs_root from memory.