linux-kernel - Re: [RFC v4 01/17] mm: introduce an additional vma bit for powerpc pkey

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Date:   Tue, 27 Jun 2017 20:54:09 +1000
From:   Balbir Singh <bsingharora@...il.com>
To:     Ram Pai <linuxram@...ibm.com>, linuxppc-dev@...ts.ozlabs.org,
        linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
        linux-mm@...ck.org, x86@...nel.org, linux-doc@...r.kernel.org,
        linux-kselftest@...r.kernel.org
Cc:     benh@...nel.crashing.org, paulus@...ba.org, mpe@...erman.id.au,
        khandual@...ux.vnet.ibm.com, aneesh.kumar@...ux.vnet.ibm.com,
        dave.hansen@...el.com, hbabu@...ibm.com, arnd@...db.de,
        akpm@...ux-foundation.org, corbet@....net, mingo@...hat.com
Subject: Re: [RFC v4 01/17] mm: introduce an additional vma bit for powerpc
 pkey

On Tue, 2017-06-27 at 03:11 -0700, Ram Pai wrote:
> Currently there are only 4bits in the vma flags to support 16 keys
> on x86.  powerpc supports 32 keys, which needs 5bits. This patch
> introduces an addition bit in the vma flags.
> 
> Signed-off-by: Ram Pai <linuxram@...ibm.com>
> ---
>  fs/proc/task_mmu.c |  6 +++++-
>  include/linux/mm.h | 18 +++++++++++++-----
>  2 files changed, 18 insertions(+), 6 deletions(-)
> 
> diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
> index f0c8b33..2ddc298 100644
> --- a/fs/proc/task_mmu.c
> +++ b/fs/proc/task_mmu.c
> @@ -666,12 +666,16 @@ static void show_smap_vma_flags(struct seq_file *m, struct vm_area_struct *vma)
>  		[ilog2(VM_MERGEABLE)]	= "mg",
>  		[ilog2(VM_UFFD_MISSING)]= "um",
>  		[ilog2(VM_UFFD_WP)]	= "uw",
> -#ifdef CONFIG_X86_INTEL_MEMORY_PROTECTION_KEYS
> +#ifdef CONFIG_ARCH_HAS_PKEYS
>  		/* These come out via ProtectionKey: */
>  		[ilog2(VM_PKEY_BIT0)]	= "",
>  		[ilog2(VM_PKEY_BIT1)]	= "",
>  		[ilog2(VM_PKEY_BIT2)]	= "",
>  		[ilog2(VM_PKEY_BIT3)]	= "",
> +#endif /* CONFIG_ARCH_HAS_PKEYS */
> +#ifdef CONFIG_PPC64_MEMORY_PROTECTION_KEYS
> +		/* Additional bit in ProtectionKey: */
> +		[ilog2(VM_PKEY_BIT4)]	= "",
>  #endif

Not sure why these are linked with smap bits, but I guess the keys live
in the Supervisor Mode Access Prevention area?

Balbir Singh.