Re: [PATCH 35/37] Set c0 status for ST0_KX on Cavium OCTEON.

["Maciej W. Rozycki" <macro@linux-mips.org>]

On Sun, 26 Oct 2008, Chad Reese wrote:

> The Octeon IO space regions are significantly larger than a 32bit kernel
> could tlb map easily. The entire range takes 49 bits to address. As a

 Do you need them all at once?  If not, you may be able to get away with 
ioremap() called on demand.

> not particularly clean, but working alternative, we enable 64bit
> addressing in the kernel and used XKPHYS to access IO. Every access was
> surrounded by a local_irq_save/local_irq_restore. Since this is ugly to
> the extreme, maybe we should drop being able to boot a 32bit kernel on
> Octeon until something better is worked out.

 Good idea anyway I would say.  With 64-bit processors support for a 
32-bit kernel may be a nice feature, but really only if it works straight 
away with no strange hacks.  Otherwise a 64-bit kernel is the obvious 
choice providing a superset of the functionality, including but not 
limited to support for the same plain 32-bit (o32) userland if need be.  
And with the GCC/GAS changes to support -msym32 that happened a while ago 
the overhead from using a 64-bit kernel has become quite negligible.

  Maciej