Re: [PATCH v3 2/2] powerpc/shared: Use static key to detect shared processor

[Waiman Long <longman@redhat.com>]

On 12/5/19 3:32 AM, Srikar Dronamraju wrote:
> With the static key shared processor available, is_shared_processor()
> can return without having to query the lppaca structure.
>
> Cc: Parth Shah <parth@linux.ibm.com>
> Cc: Ihor Pasichnyk <Ihor.Pasichnyk@ibm.com>
> Cc: Juri Lelli <juri.lelli@redhat.com>
> Cc: Phil Auld <pauld@redhat.com>
> Cc: Waiman Long <longman@redhat.com>
> Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
> ---
> Changelog v1 (https://patchwork.ozlabs.org/patch/1204192/) ->v2:
> Now that we no more refer to lppaca, remove the comment.
>
> Changelog v2->v3:
> Code is now under CONFIG_PPC_SPLPAR as it depends on CONFIG_PPC_PSERIES.
> This was suggested by Waiman Long.
>
>  arch/powerpc/include/asm/spinlock.h | 9 ++-------
>  1 file changed, 2 insertions(+), 7 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/spinlock.h b/arch/powerpc/include/asm/spinlock.h
> index de817c25deff..e83d57f27566 100644
> --- a/arch/powerpc/include/asm/spinlock.h
> +++ b/arch/powerpc/include/asm/spinlock.h
> @@ -111,13 +111,8 @@ static inline void splpar_rw_yield(arch_rwlock_t *lock) {};
>  
>  static inline bool is_shared_processor(void)
>  {
> -/*
> - * LPPACA is only available on Pseries so guard anything LPPACA related to
> - * allow other platforms (which include this common header) to compile.
> - */
> -#ifdef CONFIG_PPC_PSERIES
> -	return (IS_ENABLED(CONFIG_PPC_SPLPAR) &&
> -		lppaca_shared_proc(local_paca->lppaca_ptr));
> +#ifdef CONFIG_PPC_SPLPAR
> +	return static_branch_unlikely(&shared_processor);
>  #else
>  	return false;
>  #endif

Acked-by: Waiman Long <longman@redhat.com>