[PATCH] powerpc: Add support for userspace P9 copy paste

[Balbir Singh]

> /*
>  * System calls.
> @@ -508,6 +509,14 @@ BEGIN_FTR_SECTION
>     ldarx    r6,0,r1
> END_FTR_SECTION_IFSET(CPU_FTR_STCX_CHECKS_ADDRESS)
> 
> +BEGIN_FTR_SECTION
> +/*
> + * A cp_abort (copy paste abort) here ensures that when context switching, a
> + * copy from one process can't leak into the paste of another.
> + */
> +        PPC_CP_ABORT

I think the alignment issue has been called out, but it is not clear from the changelog that
we do this during syscall_exit/syscalls.

And also, do we need to care about preemptions, etc by the scheduler?

> +END_FTR_SECTION_IFSET(CPU_FTR_ARCH_300)
> +
> #ifdef CONFIG_PPC_BOOK3S
> /* Cancel all explict user streams as they will have no use after context
>  * switch and will stop the HW from creating streams itself