[RFC PATCH 05/17] ARM: kernel: save/restore kernel IF

[Lorenzo Pieralisi]

On Mon, Jul 11, 2011 at 05:57:29PM +0100, Frank Hofmann wrote:
> On Mon, 11 Jul 2011, Lorenzo Pieralisi wrote:
> 
> [ ... ]
> >>> The array of pointers is there to save pgdir on idle entry, one per-cpu.
> >>
> >> If you're going through cpu_{do_}suspend/resume, the TTBRs are
> >> saved/restored anyway, what do you need to keep the virtual addresses
> >> around for ?
> >>
> >
> > Because I switch mm before calling suspend, which is called
> > with a cloned pgdir. I am not sure I can avoid that.
> 
> On resume, you'll be restoring the same thread as was previously running, 
> right ? If so, all you do there is copying current->active_mm->pgd to some 
> other place ?

You are right, I will remove that code unless I can use the saved value
on resume and I cannot rely on current to be retrieved at that point.

> 
> Also, if you'd be using cpu_suspend(), would there still be a need for 
> cpu_switch_mm() before ? It'd rather be a case of possibly calling that 
> before the MMU-off sequence / cpu_resume() ?
> 
> Or is it that you use the new pgdir to make a memory region uncacheable ?

Yes, that's the reason why I switch mm (eg uncacheable memory used to
save registers through cpu_do_suspend and mapped in the cloned pgdir at boot +
some control variables used when MMU is off).

Thanks,
Lorenzo