Re: [PATCH RFC 1/4] x86/thread_info: add TIF_NOPTI to disable PTI per task

[Thomas Gleixner <tglx@linutronix.de>]

On Mon, 8 Jan 2018, Willy Tarreau wrote:

> This flag indicates that the task will not use isolated page tables.
> 
> Signed-off-by: Willy Tarreau <w@1wt.eu>
> ---
>  arch/x86/include/asm/thread_info.h | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/arch/x86/include/asm/thread_info.h b/arch/x86/include/asm/thread_info.h
> index 0022333..2f92cf1 100644
> --- a/arch/x86/include/asm/thread_info.h
> +++ b/arch/x86/include/asm/thread_info.h
> @@ -126,6 +126,14 @@ struct thread_info {
>  #define _TIF_X32		(1 << TIF_X32)
>  #define _TIF_FSCHECK		(1 << TIF_FSCHECK)
>  
> +/* The following flags only exist on x86-64. We can't use the shift anymore

Please do not use this horrible comment syle

And what's wrong with (1UL << 32)?

> + * due to C using signed ints by default and asm using unsigned longs.
> + */
> +#ifdef CONFIG_X86_64
> +# define  TIF_NOPTI		32	/* disable PTI for this task */

No tail comments please.

> +# define _TIF_NOPTI		0x0000000100000000
> +#endif
> +

Thanks,

	tglx