Xen devel - Dec 2012 - Why we relocate xen location in __start_xen method?

in ARM Archietecture.
__start_xen ()

  ----->  setup_pagetables()
            {
                    /* Calculate virt-to-phys offset for the new location */
                      phys_offset = xen_paddr - (unsigned long) _start;

                     /* Copy */
                    memcpy((void *) dest_va, _start, _end - _start);
            }

thankx
---------
Asad

On Fri, 7 Dec 2012, asad raza wrote:
> in ARM Archietecture.
> __start_xen ()
> 
>   ----->  setup_pagetables()
>             {
>                     /* Calculate virt-to-phys offset for the new location
*/
>                       phys_offset = xen_paddr - (unsigned long) _start;
> 
>                      /* Copy */
>                     memcpy((void *) dest_va, _start, _end - _start);
>             }
We relocate Xen to the top of RAM (and align to a XEN_PADDR_ALIGN
boundary) to free some precious low RAM and be independent from
the behaviour of the bootloader.
See xen/arch/arm/setup.c:get_xen_paddr.