move kernel virtual base

Hi:
 
I am using mpc8548 and linux 2.6.14.5
For some reasons, I would like to move kernel virtua base from 0xC0000000 to
0x60000000.
But I encounter many problems. (I am still trying to figure out where is the
true problem)
Does anyone know any possible problem? Any clue is welcome.
Thanks a lot.
 
I tried to move it to 0xA0000000 before. It worked fine.
 
 
                   Jay...