On Mon, Apr 04, 2016 at 09:11:12PM +1000, Anton Blanchard wrote: > In check_cpu_pa_features() we check a number of bits in the > ibm,pa-features array and set and clear CPU features based on what > we find. One of these bits is CPU_FTR_TM, the transactional memory > feature bit. > > If this does disable TM at runtime, then we need to tell userspace > about it by clearing the user CPU feature bits. > > Without this patch userspace processes will think they can execute > TM instructions and get killed when they try. > > Signed-off-by: Anton Blanchard <an...@samba.org>
Reviewed-by: David Gibson <da...@gibson.dropbear.id.au>
> Cc: sta...@vger.kernel.org
> ---
>
> Michael I've added stable here because I'm seeing this on a number
> of distros and would like to get it backported, but I'll leave it up
> to you if it should go there.
>
> diff --git a/arch/powerpc/kernel/setup_64.c b/arch/powerpc/kernel/setup_64.c
> index f98be83..98c6c86 100644
> --- a/arch/powerpc/kernel/setup_64.c
> +++ b/arch/powerpc/kernel/setup_64.c
> @@ -822,4 +822,18 @@ static int __init disable_hardlockup_detector(void)
> return 0;
> }
> early_initcall(disable_hardlockup_detector);
> +
> +static int __init update_cpu_user_features(void)
> +{
> + /*
> + * Firmware might have disabled TM by clearing the relevant
> + * bit in the ibm,pa-features array. In this case we need to
> + * tell userspace.
> + */
> + if (!cpu_has_feature(CPU_FTR_TM))
> + cur_cpu_spec->cpu_user_features2 &=
> ~(PPC_FEATURE2_HTM|PPC_FEATURE2_HTM_NOSC);
> +
> + return 0;
> +}
> +early_initcall(update_cpu_user_features);
> #endif
>
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
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