Re: [PATCH] Use a sensible tlbex default for unknown CPUs

[Thiemo Seufer <ths@networkno.de>]

Maciej W. Rozycki wrote:
> On Thu, 25 Oct 2007, Thiemo Seufer wrote:
> 
> > currently the kernel panics when it boots on an unknown CPU model
> > (with an unknown PRID). Based on the assumption that the majority
> > of newly supported CPU will conform to Release 2 standard, I wrote
> > the appended patch which handles unknown CPUs as R2. It isn't
> > completely bulletproof, as (yet unsupported) non-R1/R2 CPUs may
> > use the AT config bits for different purposes. I still think this
> > is good enough a test.
> 
>  Good idea in general, but do we have to rely on the undefined?  How 
> about this:
> 
> > +           /* Panic if this isn't a Release 2 CPU. */
> > +           if (!((read_c0_config() & MIPS_CONF_AT) >> 13)) {
> 
>       if (!(current_cpu_data.isa_level &
>             (MIPS_CPU_ISA_M64R2 | MIPS_CPU_ISA_M32R2))) {
> 
> instead for example?

This is circular, as isa_level won't be initialized for a unknown CPU.
The *_r2 check suggested by Ralf has the same problem AFAICS, so it
looks like we have to stick with the original solution.


Thiemo