linux-kernel - Re: [PATCH 2/8] mm, powerpc, x86: introduce an additional vma bit for powerpc pkey

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Message-Id: <20180508161828.GA5474@ram.oc3035372033.ibm.com>
Date:   Tue, 8 May 2018 09:18:28 -0700
From:   Ram Pai <linuxram@...ibm.com>
To:     Michael Ellerman <mpe@...erman.id.au>
Cc:     mingo@...hat.com, linuxppc-dev@...abs.org, linux-mm@...ck.org,
        x86@...nel.org, linux-kernel@...r.kernel.org, dave.hansen@...el.com
Subject: Re: [PATCH 2/8] mm, powerpc, x86: introduce an additional vma bit
 for powerpc pkey

On Wed, May 09, 2018 at 12:59:42AM +1000, Michael Ellerman wrote:
> From: Ram Pai <linuxram@...ibm.com>
> 
> Currently only 4bits are allocated in the vma flags to hold 16
> keys. This is sufficient for x86. PowerPC  supports  32  keys,
> which needs 5bits. This patch allocates an  additional bit.
> 
> Reviewed-by: Ingo Molnar <mingo@...nel.org>
> Acked-by: Balbir Singh <bsingharora@...il.com>
> Signed-off-by: Ram Pai <linuxram@...ibm.com>
> [mpe: Fold in #if VM_PKEY_BIT4 as noticed by Dave Hansen]
> Signed-off-by: Michael Ellerman <mpe@...erman.id.au>
> ---
>  fs/proc/task_mmu.c | 3 +++
>  include/linux/mm.h | 3 ++-
>  2 files changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
> index 541392a62608..c2163606e6fb 100644
> --- a/fs/proc/task_mmu.c
> +++ b/fs/proc/task_mmu.c
> @@ -679,6 +679,9 @@ static void show_smap_vma_flags(struct seq_file *m, struct vm_area_struct *vma)
>  		[ilog2(VM_PKEY_BIT1)]	= "",
>  		[ilog2(VM_PKEY_BIT2)]	= "",
>  		[ilog2(VM_PKEY_BIT3)]	= "",
> +#if VM_PKEY_BIT4
> +		[ilog2(VM_PKEY_BIT4)]	= "",
> +#endif
>  #endif /* CONFIG_ARCH_HAS_PKEYS */
>  	};
>  	size_t i;
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index c6a6f2492c1b..abfd758ff83a 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -231,9 +231,10 @@ extern unsigned int kobjsize(const void *objp);
>  #ifdef CONFIG_ARCH_HAS_PKEYS
>  # define VM_PKEY_SHIFT	VM_HIGH_ARCH_BIT_0
>  # define VM_PKEY_BIT0	VM_HIGH_ARCH_0	/* A protection key is a 4-bit value */
> -# define VM_PKEY_BIT1	VM_HIGH_ARCH_1
> +# define VM_PKEY_BIT1	VM_HIGH_ARCH_1	/* on x86 and 5-bit value on ppc64   */
>  # define VM_PKEY_BIT2	VM_HIGH_ARCH_2
>  # define VM_PKEY_BIT3	VM_HIGH_ARCH_3
> +# define VM_PKEY_BIT4	VM_HIGH_ARCH_4
>  #endif /* CONFIG_ARCH_HAS_PKEYS */

this has to be: 

+#if defined(CONFIG_PPC)
+# define VM_PKEY_BIT4  VM_HIGH_ARCH_4
+#else
+# define VM_PKEY_BIT4  0
+#endif