powerpc: Add user-return-notifier support

[Ananth N Mavinakayanahalli]

On Tue, Sep 08, 2015 at 07:24:39PM +1000, Michael Ellerman wrote:
> On Wed, 2015-09-02 at 10:39 +0530, Ananth N Mavinakayanahalli wrote:
> > On Tue, Sep 01, 2015 at 10:29:12PM -0500, Scott Wood wrote:
> > 
> > > Why is this selected by KVM on PPC if KVM on PPC doesn't use it?  What is the 
> > > user you're trying to enable?
> > 
> > I copied Paul and Gautham to get their thoughts on whether it is
> > something they could use on Power. At this time, apart from enabling the
> > feature, I do not have a specific usecase for it. We can park this patch
> > pending a real user on powerpc.
> 
> OK, thanks for hashing that out guys. I think parking it is the best solution
> for now, we could merge it and disable it somehow, but that would be ugly and
> prone to breaking.
> 
> Do we want to do something like this?

Yes. This looks fine -- folks who want it down the line know where to look.

Thanks,
Ananth

> 
> cheers
> 
> diff --git a/Documentation/features/arch-support.txt b/Documentation/features/arch-support.txt
> index d22a1095e661..3e2cf6161cf4 100644
> --- a/Documentation/features/arch-support.txt
> +++ b/Documentation/features/arch-support.txt
> @@ -8,4 +8,5 @@ The meaning of entries in the tables is:
>      | ok |  # feature supported by the architecture
>      |TODO|  # feature not yet supported by the architecture
>      | .. |  # feature cannot be supported by the hardware
> +    |n/a |  # feature is not needed/wanted/meaningful for the architecture
> 
> diff --git a/Documentation/features/debug/user-ret-profiler/arch-support.txt b/Documentation/features/debug/user-ret-profiler/arch-support.txt
> index 44cc1ff3f603..669813180dc5 100644
> --- a/Documentation/features/debug/user-ret-profiler/arch-support.txt
> +++ b/Documentation/features/debug/user-ret-profiler/arch-support.txt
> @@ -27,7 +27,7 @@
>      |       nios2: | TODO |
>      |    openrisc: | TODO |
>      |      parisc: | TODO |
> -    |     powerpc: | TODO |
> +    |     powerpc: | n/a  |    # http://lkml.kernel.org/r/20150825054110.GD3815@in.ibm.com
>      |        s390: | TODO |
>      |       score: | TODO |
>      |          sh: | TODO |
> 
>