[PATCH 16/19] powerpc: create giveup_all()

[Michael Ellerman]

On Thu, 2015-10-29 at 11:44 +1100, Anton Blanchard wrote:

> Create a single function that gives everything up (FP, VMX, VSX, SPE).
> Doing this all at once means we only do one MSR write.
> 
> A context switch microbenchmark using yield():
> 
> http://ozlabs.org/~anton/junkcode/context_switch2.c
> 
> ./context_switch2 --test=yield --fp --altivec --vector 0 0
> 
> shows an improvement of 3% on POWER8.
> 
> Signed-off-by: Anton Blanchard <anton at samba.org>
> ---
>  arch/powerpc/include/asm/switch_to.h |  1 +
>  arch/powerpc/kernel/process.c        | 75 ++++++++++++++++++++++++++++--------
>  arch/powerpc/kvm/book3s_pr.c         | 17 +-------

books3s_pr.c can be a module, so we need giveup_all() to be EXPORT_SYMBOL.

I'll fix it up on my end.

cheers