Executing program from XRAM

Is is possible with the 8051 architecture
to copy a program or function into XRAM
and execute it? Or do the separate
code/data address spaces prevent this?

What I'm trying to do is to write a boot
loader that can put the loader routine
into flash, so that the flash chip
the boot loader resides in can be erased
and re-written. The plan is NOT to
update the boot loader portion of the flash,
but the application portion.

The flash chip we're using doesn't allow
you to execute out of the flash if
any portion of the flash is being
programmed.

We're using the Philips 87C51MB2 chip,
which is an MX part.

Thanks,

Ed