[PATCH V2 4/8] powerpc: Explicitly disable math features when copying thread

[Michael Neuling]

On Fri, 2016-01-15 at 16:04 +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.

Is this a bug in the current code?

Mikey

> 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 dccc87e..e0c3d2d 100644
> --- a/arch/powerpc/kernel/process.c
> +++ b/arch/powerpc/kernel/process.c
> @@ -1307,6 +1307,7 @@ int copy_thread(unsigned long clone_flags,
> unsigned long usp,
>  
>  		f = ret_from_fork;
>  	}
> +	childregs->msr &= ~(MSR_FP|MSR_VEC|MSR_VSX);
>  	sp -= STACK_FRAME_OVERHEAD;
>  
>  	/*