Re: [rfc][patch] mm: use a pte bit to flag normal pages

[Nick Piggin <npiggin@suse.de>]

On Tue, Jan 08, 2008 at 03:37:46AM +0100, Andi Kleen wrote:
> > - strongly ordered
> > - bufferable only *
> > - device, sharable *
> > - device, unsharable
> > - memory, bufferable and cacheable, write through, no write allocate
> > - memory, bufferable and cacheable, write back, no write allocate
> > - memory, bufferable and cacheable, write back, write allocate
> > - implementation defined combinations (eg, selecting "minicache")
> > - and a set of 16 states to allow the policy of inner and outer levels
> >   of cache to be defined (two bits per level).
> 
> Do you need all of those in user space? Perhaps you could give
> the bits different meanings depending on user or kernel space.
> I think Nick et.al. just need the bits for user space; they won't
> care about kernel mappings.

Yes correct -- they are only for userspace mappings. Though that includes mmaps
of /dev/mem and device drivers etc. 

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