[RFC v5 11/38] mm: introduce an additional vma bit for powerpc pkey
Ram Pai
linuxram at us.ibm.com
Thu Jul 13 08:23:31 AEST 2017
On Tue, Jul 11, 2017 at 11:10:46AM -0700, Dave Hansen wrote:
> On 07/05/2017 02:21 PM, 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 at us.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
>
> I'd probably just leave the #ifdef out and eat the byte or whatever of
> storage that this costs us on x86.
fine with me.
>
> > };
> > size_t i;
> > diff --git a/include/linux/mm.h b/include/linux/mm.h
> > index 7cb17c6..3d35bcc 100644
> > --- a/include/linux/mm.h
> > +++ b/include/linux/mm.h
> > @@ -208,21 +208,29 @@ extern int overcommit_kbytes_handler(struct ctl_table *, int, void __user *,
> > #define VM_HIGH_ARCH_BIT_1 33 /* bit only usable on 64-bit architectures */
> > #define VM_HIGH_ARCH_BIT_2 34 /* bit only usable on 64-bit architectures */
> > #define VM_HIGH_ARCH_BIT_3 35 /* bit only usable on 64-bit architectures */
> > +#define VM_HIGH_ARCH_BIT_4 36 /* bit only usable on 64-bit arch */
>
> Please just copy the above lines.
Just copying over makes checkpatch.pl unhappy. It exceeds 80 columns.
>
> > #define VM_HIGH_ARCH_0 BIT(VM_HIGH_ARCH_BIT_0)
> > #define VM_HIGH_ARCH_1 BIT(VM_HIGH_ARCH_BIT_1)
> > #define VM_HIGH_ARCH_2 BIT(VM_HIGH_ARCH_BIT_2)
> > #define VM_HIGH_ARCH_3 BIT(VM_HIGH_ARCH_BIT_3)
> > +#define VM_HIGH_ARCH_4 BIT(VM_HIGH_ARCH_BIT_4)
> > #endif /* CONFIG_ARCH_USES_HIGH_VMA_FLAGS */
> >
> > -#if defined(CONFIG_X86)
> > -# define VM_PAT VM_ARCH_1 /* PAT reserves whole VMA at once (x86) */
> > -#if defined (CONFIG_X86_INTEL_MEMORY_PROTECTION_KEYS)
> > +#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_BIT0 VM_HIGH_ARCH_0
> > # define VM_PKEY_BIT1 VM_HIGH_ARCH_1
> > # define VM_PKEY_BIT2 VM_HIGH_ARCH_2
> > # define VM_PKEY_BIT3 VM_HIGH_ARCH_3
> > -#endif
> > +#endif /* CONFIG_ARCH_HAS_PKEYS */
>
> We have the space here, so can we just say that it's 4-bits on x86 and 5
> on ppc?
sure.
>
> > +#if defined(CONFIG_PPC64_MEMORY_PROTECTION_KEYS)
> > +# define VM_PKEY_BIT4 VM_HIGH_ARCH_4 /* additional key bit used on ppc64 */
> > +#endif /* CONFIG_PPC64_MEMORY_PROTECTION_KEYS */
>
> Why bother #ifdef'ing a #define?
ok.
RP
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