[RFC PATCH 2/9] powerpc/mm/book3s-64: Free up 7 high-order bits in the Linux PTE

[Paul Mackerras]

On Sat, Feb 20, 2016 at 09:46:19PM +0530, Aneesh Kumar K.V wrote:
> Paul Mackerras <paulus at samba.org> writes:
> 
> > This frees up bits 57-63 in the Linux PTE on 64-bit Book 3S machines.
> > In the 4k page case, this is done just by reducing the size of the
> > RPN field to 39 bits, giving 51-bit real addresses.  In the 64k page
> > case, we had 10 unused bits in the middle of the PTE, so this moves
> > the RPN field down 10 bits to make use of those unused bits.  This
> > means the RPN field is now 3 bits larger at 37 bits, giving 53-bit
> > real addresses in the normal case, or 49-bit real addresses for the
> > special 4k PFN case.
> 
> 
> Is it ok to have different real address bits between 4k and 64k linux
> config ?

Do you mean a different number of address bits, or a different
location?  In fact both were different before this patch anyway.

Paul.