Some comment, first the above negate conditional
looks rather ugly, I'd rather do a

#if defined(CONFIG_4xx) || defined(CONFIG_BOOKE)
	dbcr0 case
#else
	dabr case
#endif

Yes, it makes sense. I'll switch it around.

second I wonder why we have the notify_die only for one case, that seems
rather odd.  Looking further the notify_die is even more odd because
DIE_DABR_MATCH doesn't actually appear anywhere else in the kernel.
I'd suggest simply removing it.

DIE_DABR_MATCH doesn't appear anywhere else because there is only a
single function responsible for handling the DABR/DAC events on powerPC
with this modification. It would make sense to call this to both the
DAC/DABR cases though (i.e. taking it out of the #ifdef), what do you
think?

Can you redo this in the normal Linux comment style, ala:

	/*
	 * For processors using DABR (i.e. 970), the bottom 3 bits are flags.
	 *  It was assumed, on previous implementations, that 3 bits were
	 *  passed together with the data address, fitting the design of the
	 *  DABR register, as follows:
	 *
	 *  bit 0: Read flag
	 *  bit 1: Write flag
	 *  bit 2: Breakpoint translation
	 *
	 *  Thus, we use them here as so.
	 */

and similar in few other places.

Will do, thanks for reviewing this one.

Regards,
Luis