[1/6] powerpc/64s: Add barrier_nospec

[Michael Ellerman]

On Tue, 2018-04-24 at 04:15:54 UTC, Michael Ellerman wrote:
> From: Michal Suchanek <msuchanek at suse.de>
> 
> A no-op form of ori (or immediate of 0 into r31 and the result stored
> in r31) has been re-tasked as a speculation barrier. The instruction
> only acts as a barrier on newer machines with appropriate firmware
> support. On older CPUs it remains a harmless no-op.
> 
> Implement barrier_nospec using this instruction.
> 
> mpe: The semantics of the instruction are believed to be that it
> prevents execution of subsequent instructions until preceding branches
> have been fully resolved and are no longer executing speculatively.
> There is no further documentation available at this time.
> 
> Signed-off-by: Michal Suchanek <msuchanek at suse.de>
> Signed-off-by: Michael Ellerman <mpe at ellerman.id.au>

Series applied to powerpc next.

https://git.kernel.org/powerpc/c/a6b3964ad71a61bb7c61d80a60bea7

cheers