[PATCH v3 1/6] powerpc/mm: any thread in one core can be the first to setup TLB1

[Denis Kirjanov]

On 11/20/15, Chenhui Zhao <chenhui.zhao at freescale.com> wrote:
> On e6500, in the case of cpu hotplug, either thread in one core
> may be the first thread initilzing the TLB1. The subsequent threads
> must not setup it again.
>
> The code is derived from the comment of Scott Wood.
>
> Signed-off-by: Chenhui Zhao <chenhui.zhao at freescale.com>
> ---
>  arch/powerpc/include/asm/cputhreads.h | 7 +++++++
>  arch/powerpc/mm/tlb_nohash.c          | 4 +---
>  2 files changed, 8 insertions(+), 3 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/cputhreads.h
> b/arch/powerpc/include/asm/cputhreads.h
> index ba42e46..b56cece 100644
> --- a/arch/powerpc/include/asm/cputhreads.h
> +++ b/arch/powerpc/include/asm/cputhreads.h
> @@ -94,6 +94,13 @@ static inline int cpu_last_thread_sibling(int cpu)
>  	return cpu | (threads_per_core - 1);
>  }
>
> +static inline u32 get_tensr(void)
> +{
> +	if (cpu_has_feature(CPU_FTR_SMT))
> +		return mfspr(SPRN_TENSR);
> +	else
> +		return 1;
> +}
If i get it right, SPRN_TENSR used in the code only if CONFIG_PPC64
is defined. Then we can make it noop on ppc32.

Thanks!

>
>  #endif /* _ASM_POWERPC_CPUTHREADS_H */
> diff --git a/arch/powerpc/mm/tlb_nohash.c b/arch/powerpc/mm/tlb_nohash.c
> index bb04e4d..f466848 100644
> --- a/arch/powerpc/mm/tlb_nohash.c
> +++ b/arch/powerpc/mm/tlb_nohash.c
> @@ -640,9 +640,7 @@ static void early_init_this_mmu(void)
>  		 * transient mapping would cause problems.
>  		 */
>  #ifdef CONFIG_SMP
> -		if (cpu != boot_cpuid &&
> -		    (cpu != cpu_first_thread_sibling(cpu) ||
> -		     cpu == cpu_first_thread_sibling(boot_cpuid)))
> +		if (hweight32(get_tensr()) > 1)
>  			map = false;
>  #endif
>
> --
> 1.9.1
>
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