Subject: Re: [PATCH 2/2] powerpc/mm: don't do tlbie for updatepp request with NO HPTE fault

From: Benjamin Herrenschmidt <[email-masked]>
Date: Tue, 02 Dec 2014 10:59:37 +1100

On Mon, 2014-11-03 at 20:21 +0530, Aneesh Kumar K.V wrote:
> --- a/arch/powerpc/mm/hash_native_64.c
> +++ b/arch/powerpc/mm/hash_native_64.c
> @@ -283,11 +283,11 @@ static long native_hpte_remove(unsigned long hpte_group)
>  
>  static long native_hpte_updatepp(unsigned long slot, unsigned long newpp,
>                                  unsigned long vpn, int bpsize,
> -                                int apsize, int ssize, int local)
> +                                int apsize, int ssize, unsigned long flags)
>  {
>         struct hash_pte *hptep = htab_address + slot;
>         unsigned long hpte_v, want_v;
> -       int ret = 0;
> +       int ret = 0, local = 0;
>  
>         want_v = hpte_encode_avpn(vpn, bpsize, ssize);
>  
> @@ -322,8 +322,15 @@ static long native_hpte_updatepp(unsigned long slot, unsigned long newpp,
>                 }
>                 native_unlock_hpte(hptep);
>         }
> -       /* Ensure it is out of the tlb too. */
> -       tlbie(vpn, bpsize, apsize, ssize, local);
> +
> +       if (flags & HPTE_LOCAL_UPDATE)
> +               local = 1;
> +       /*
> +        * Ensure it is out of the tlb too if it is not a nohpte fault
> +        */
> +       if (!(flags & HPTE_NOHPTE_UPDATE))
> +               tlbie(vpn, bpsize, apsize, ssize, local);
> +
>         return ret;
>  }

An additional refinement we discussed that I'd like you to test/measure
is to basically always be local for updatepp unless we have a flag that
forces us not to.

That flag would be set by copro faults only.

Can you do something on top of this series ?

Cheers,
Ben.