RE: [PATCH v2 08/25] powerpc/8xx: Map IMMR area with 512k page at a fixed address

From: David Laight
Date: Fri Sep 25 2015 - 10:48:00 EST

From: Scott Wood
> Sent: 24 September 2015 21:14
> > Isn't this a more general problem?
> >
> > If there are multiple remap requests for the same physical page
> > shouldn't the kernel be just increasing a reference count somewhere
> > and returning address in the same virtual page?
> > This should probably happen regardless of the address.
> > I presume it must be done for cacheable mappings.
> Why would you assume that?

Because 'really horrid (tm)' things happen on some cache
architectures if you map the same physical address to
multiple virtual addresses.