Probing for native availability of isel from userspace

[malc]

On Sun, 23 Sep 2012, Benjamin Herrenschmidt wrote:

> On Sat, 2012-09-22 at 21:08 +0200, Segher Boessenkool wrote:
> > > Thanks for suggestion, but i'd rather not play with heuristics.
> > 
> > Have a look at /sys/kernel/debug/powerpc/emulated_instructions/ then?
> 
> Userspace should *NEVER* rely on the content of debugfs, it will change
> with time, it is not a guaranteed ABI, it's purely for people to look
> at... for debugging.

Furthermore this box simply doesn't have it built-in...

> 
> Unfortunately we don't expose ISEL support via features (maybe we
> should, this is reasonably easy to fix, except that we are running short
> on feature bits and adding a new set of bits isn't totally trivial).
> 
> At this stage I would recommend using arch 2.06 as your key/trigger and
> either add a handful of known PVR values (mfpvr is emulated) for other
> CPUs you know support it (there shouldn't be that many), or just do the
> heuristic :-(
> 

Thank you.

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