Re: [patch] pageattr update

[David Mosberger <davidm@napali.hpl.hp.com>]

Hi Ben,

I'm have a concern about the current change_page_attr() patch.  It
gives the impression that the GART memory always gets mapped
write-combined.  This is not always true.  For example, on IA-64,
attribute-aliasing issues are prevented by requiring IA-64 platforms
to use coherent AGP DMA.  In other words, the AGP memory will be
mapped writeback, as usual.

As long as change_page_attr() is used for AGP-related stuff only,
there is probably no real issue with the patch in its current form
(its simply a no-op on most non-x86 platforms).  However, I'm a bit
worried that someone might start to use it for other things, such that
change_page_attr() could no longer be a no-op on those platforms.
Since the DMA coherency issue is an AGP specific issue, perhaps just
renaming the macro to agp_change_page_attr() would take care of my
concern.  What do you think?

	--david