Re: FPU emulator unsafe for SMP?

[Ralf Baechle <ralf@oss.sgi.com>]

On Tue, Feb 19, 2002 at 05:12:38PM -0800, Jun Sun wrote:

> > It's gotta be done.  I mean, the last I heard (which was a long
> > time ago) mips64 Linux was keeping the CPU node number in
> > a watchpoint register (or something equally unwholesome)
> 
> It seems that people are getting smarter by putting cpu id to
> context register.  In fact isn't this part of new MIPS
> standard?

The context register is actually intended to be used for indexing a flat
4mb array of pagetables on a 32-bit processor.  It's a bit ill-defined
on R4000-class processors as it assumes a size of 8 bytes per pte, so
cannot be used in the Linux/MIPS kernel without shifting bits around.
Also in case of Linux it means entering the world of cache aliases ...

  Ralf