[PATCH 2/3] powerpc: Instrument Hypervisor Calls: add wrappers

[Olof Johansson]

On Tue, Jul 18, 2006 at 04:18:15PM -0700, Mike Kravetz wrote:

> I assume checking must be done at run time via something like,
> if (cpu_has_feature(CPU_FTR_PURR))

If you do it in the hcall asm instead (like Paulus suggested), then it's
better to use BEGIN_FTR_SECTION/END_FTR_SECTION() around it, that way
the PURR reads just get nopped out instead of adding tests and branches.

> Also assume that it would make sense to do this determination at
> initialization/boot time and put the result in the statistic data
> structure.  In this way we would know it is in the same cache line
> we are updating with other stats.  Or, should cur_cpu_spec->cpu_features
> be 'sufficiently hot' to make this a non-issue?

If you use the FTR_SECTION stuff then it'll be taken care of
automatically at boot time. Doing that from C is messy, I don't think
anyone has had reason to do it before.


-Olof