[PATCH 4/8] powerpc: Explicitly disable math features when copying thread

[Michael Neuling]

On Wed, 2015-11-18 at 14:26 +1100, Cyril Bur wrote:
> With threads leaving the math bits enabled in their saved MSR to
> indicate
> that the hardware is hot and a restore is not needed, children need
> to turn
> it off as when they do get scheduled, there's no way their registers
> could
> have been hot.
> 
> Signed-off-by: Cyril Bur <cyrilbur at gmail.com>
> ---
>  arch/powerpc/kernel/process.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/arch/powerpc/kernel/process.c
> b/arch/powerpc/kernel/process.c
> index 398f7bf..441d9e5 100644
> --- a/arch/powerpc/kernel/process.c
> +++ b/arch/powerpc/kernel/process.c
> @@ -1243,6 +1243,7 @@ int copy_thread(unsigned long clone_flags,
> unsigned long usp,
>  
>  		f = ret_from_fork;
>  	}
> +	childregs->msr &= ~(MSR_FP|MSR_VEC|MSR_VSX);

Is this a current bug? 

Mikey

>  	sp -= STACK_FRAME_OVERHEAD;
>  
>  	/*