Subject: Re: [PATCH] PPC: BOOK3S: Disable/Enable TM looking at the ibm, pa-features device tree entry

From: Michael Neuling <[email-masked]>
Date: Thu, 01 May 2014 15:01:40 +1000

Aneesh Kumar K.V <[email-masked]> wrote:

> Runtime disable transactional memory feature looking at pa-features
> device tree entry. This provides a mechanism to disable TM on P8
> systems.

What are we actually achieving with this?

> Signed-off-by: Aneesh Kumar K.V <[email-masked]>
> ---
>  arch/powerpc/kernel/prom.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/arch/powerpc/kernel/prom.c b/arch/powerpc/kernel/prom.c
> index 668aa4791fd7..537bd7e7db0b 100644
> --- a/arch/powerpc/kernel/prom.c
> +++ b/arch/powerpc/kernel/prom.c
> @@ -161,6 +161,11 @@ static struct ibm_pa_feature {
>  	{CPU_FTR_NODSISRALIGN, 0, 0,	1, 1, 1},
>  	{0, MMU_FTR_CI_LARGE_PAGE, 0,	1, 2, 0},
>  	{CPU_FTR_REAL_LE, PPC_FEATURE_TRUE_LE, 5, 0, 0},
> +	/*
> +	 * We should use CPU_FTR_TM_COMP so that if we disable TM, it won't get
> +	 * enabled via device tree
> +	 */
> +	{CPU_FTR_TM_COMP, 0, 0,		22, 0, 0},

What does this do to guests?  Will it turn TM unavailable into an
illegal instruction?

Mikey

>  };
>  
>  static void __init scan_features(unsigned long node, unsigned char *ftrs,
> -- 
> 1.9.1
> 
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