Re: [RFC PATCH 6/6] ARM: mm: Transparent huge page support for non-LPAE systems.

[Steve Capper <steve.capper@arm.com>]

On Fri, Jan 04, 2013 at 05:04:57AM +0000, Christoffer Dall wrote:
> On Thu, Oct 18, 2012 at 12:15 PM, Steve Capper <steve.capper@arm.com> wrote:
> > Much of the required code for THP has been implemented in the earlier non-LPAE
> > HugeTLB patch.
> >
> > One more domain bits is used (to store whether or not the THP is splitting).
> 
> s/bits/bit/
> 
Thanks.

> >
> > Some THP helper functions are defined; and we have to re-define pmd_page such
> > that it distinguishes between page tables and sections.
> 
> super nit: not sure the semi-colon is warranted here.
> 
Cheers, it is a superfluous semicolon.

> >
> > Signed-off-by: Will Deacon <will.deacon@arm.com>
> > Signed-off-by: Steve Capper <steve.capper@arm.com>
> > ---
> >  arch/arm/Kconfig                      |    2 +-
> >  arch/arm/include/asm/pgtable-2level.h |   68 ++++++++++++++++++++++++++++++++-
> >  arch/arm/include/asm/pgtable-3level.h |    2 +
> >  arch/arm/include/asm/pgtable.h        |    7 +++-
> >  4 files changed, 75 insertions(+), 4 deletions(-)
> >
> > diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
> > index 9621d5f..d459673 100644
> > --- a/arch/arm/Kconfig
> > +++ b/arch/arm/Kconfig
> > @@ -1773,7 +1773,7 @@ config SYS_SUPPORTS_HUGETLBFS
> >
> >  config HAVE_ARCH_TRANSPARENT_HUGEPAGE
> >         def_bool y
> > -       depends on ARM_LPAE
> > +       depends on SYS_SUPPORTS_HUGETLBFS
> >
> >  source "mm/Kconfig"
> >
> > diff --git a/arch/arm/include/asm/pgtable-2level.h b/arch/arm/include/asm/pgtable-2level.h
> > index 34f4775..67eabb4 100644
> > --- a/arch/arm/include/asm/pgtable-2level.h
> > +++ b/arch/arm/include/asm/pgtable-2level.h
> > @@ -179,6 +179,13 @@ static inline pmd_t *pmd_offset(pud_t *pud, unsigned long addr)
> >                 clean_pmd_entry(pmdp);  \
> >         } while (0)
> >
> > +
> 
> stray whitespace?
> 

Thanks.

> > +#ifdef CONFIG_TRANSPARENT_HUGEPAGE
> > +#define _PMD_HUGE(pmd) ((pmd_val(pmd) & PMD_TYPE_MASK) == PMD_TYPE_SECT)
> > +#else
> > +#define _PMD_HUGE(pmd) (0)
> > +#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
> > +
> >  /* we don't need complex calculations here as the pmd is folded into the pgd */
> >  #define pmd_addr_end(addr,end) (end)
> >
> > @@ -197,7 +204,6 @@ static inline pmd_t *pmd_offset(pud_t *pud, unsigned long addr)
> >
> >  #define HPAGE_SHIFT             PMD_SHIFT
> >  #define HPAGE_SIZE              (_AC(1, UL) << HPAGE_SHIFT)
> > -#define HPAGE_MASK              (~(HPAGE_SIZE - 1))
> >  #define HUGETLB_PAGE_ORDER      (HPAGE_SHIFT - PAGE_SHIFT)
> >
> >  #define HUGE_LINUX_PTE_COUNT       (PAGE_OFFSET >> HPAGE_SHIFT)
> > @@ -209,6 +215,7 @@ static inline pmd_t *pmd_offset(pud_t *pud, unsigned long addr)
> >   */
> >  #define PMD_DSECT_DIRTY                (_AT(pmdval_t, 1) << 5)
> >  #define PMD_DSECT_AF           (_AT(pmdval_t, 1) << 6)
> > +#define PMD_DSECT_SPLITTING    (_AT(pmdval_t, 1) << 7)
> >
> >  #define PMD_BIT_FUNC(fn,op) \
> >  static inline pmd_t pmd_##fn(pmd_t pmd) { pmd_val(pmd) op; return pmd; }
> > @@ -261,8 +268,67 @@ static inline pmd_t pmd_modify(pmd_t pmd, pgprot_t newprot)
> >         return __pmd(pmdval);
> >  }
> >
> > +#else
> > +#define        HPAGE_SIZE      0
> 
> why this and the conditional define of _PMD_HUGE, you could just do
> like in pgtable.h and put the #ifdef around the condition in
> pmd_page(pmt_t pmd).
> 

Thanks, I'll take a look at this.

> >  #endif /* CONFIG_SYS_SUPPORTS_HUGETLBFS */
> >
> > +#define HPAGE_MASK              (~(HPAGE_SIZE - 1))
> > +
> > +#ifdef CONFIG_TRANSPARENT_HUGEPAGE
> > +#define pmd_mkhuge(pmd)                (__pmd((pmd_val(pmd) & ~PMD_TYPE_MASK) | PMD_TYPE_SECT))
> > +
> > +PMD_BIT_FUNC(mkold, &= ~PMD_DSECT_AF);
> > +PMD_BIT_FUNC(mksplitting, |= PMD_DSECT_SPLITTING);
> > +PMD_BIT_FUNC(mkdirty, |= PMD_DSECT_DIRTY);
> > +PMD_BIT_FUNC(mkyoung, |= PMD_DSECT_AF);
> > +PMD_BIT_FUNC(mkwrite, |= PMD_SECT_AP_WRITE);
> > +PMD_BIT_FUNC(mknotpresent, &= ~PMD_TYPE_MASK);
> > +
> > +#define pmd_trans_splitting(pmd)       (pmd_val(pmd) & PMD_DSECT_SPLITTING)
> > +#define pmd_young(pmd)                 (pmd_val(pmd) & PMD_DSECT_AF)
> > +#define pmd_write(pmd)                 (pmd_val(pmd) & PMD_SECT_AP_WRITE)
> > +#define pmd_trans_huge(pmd)            ((pmd_val(pmd) & PMD_TYPE_MASK) == PMD_TYPE_SECT)
> > +
> > +static inline unsigned long pmd_pfn(pmd_t pmd)
> > +{
> > +       /*
> > +        * for a section, we need to mask off more of the pmd
> > +        * before looking up the pfn
> > +        */
> > +       if ((pmd_val(pmd) & PMD_TYPE_MASK) == PMD_TYPE_SECT)
> > +               return __phys_to_pfn(pmd_val(pmd) & HPAGE_MASK);
> > +       else
> > +               return __phys_to_pfn(pmd_val(pmd) & PHYS_MASK);
> > +}
> > +
> > +static inline pmd_t pfn_pmd(unsigned long pfn, pgprot_t prot)
> > +{
> > +       pmd_t pmd = __pmd(__pfn_to_phys(pfn) | PMD_SECT_AP_READ | PMD_SECT_nG);
> > +
> > +       return pmd_modify(pmd, prot);
> > +}
> > +
> > +#define mk_pmd(page,prot) pfn_pmd(page_to_pfn(page),prot);
> > +
> > +static inline int has_transparent_hugepage(void)
> > +{
> > +       return 1;
> > +}
> > +
> > +#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
> > +
> > +static inline struct page *pmd_page(pmd_t pmd)
> > +{
> > +       /*
> > +        * for a section, we need to mask off more of the pmd
> > +        * before looking up the page as it is a section descriptor.
> > +        */
> > +       if (_PMD_HUGE(pmd))
> > +               return phys_to_page(pmd_val(pmd) & HPAGE_MASK);
> > +
> > +       return phys_to_page(pmd_val(pmd) & PHYS_MASK);
> > +}
> > +
> >  #endif /* __ASSEMBLY__ */
> >
> >  #endif /* _ASM_PGTABLE_2LEVEL_H */
> > diff --git a/arch/arm/include/asm/pgtable-3level.h b/arch/arm/include/asm/pgtable-3level.h
> > index 31c071f..8360814 100644
> > --- a/arch/arm/include/asm/pgtable-3level.h
> > +++ b/arch/arm/include/asm/pgtable-3level.h
> > @@ -197,6 +197,8 @@ PMD_BIT_FUNC(mknotpresent, &= ~PMD_TYPE_MASK);
> >  #define pfn_pmd(pfn,prot)      (__pmd(((phys_addr_t)(pfn) << PAGE_SHIFT) | pgprot_val(prot)))
> >  #define mk_pmd(page,prot)      pfn_pmd(page_to_pfn(page),prot)
> >
> > +#define pmd_page(pmd)           pfn_to_page(__phys_to_pfn(pmd_val(pmd) & PHYS_MASK))
> > +
> >  static inline pmd_t pmd_modify(pmd_t pmd, pgprot_t newprot)
> >  {
> >         const pmdval_t mask = PMD_SECT_USER | PMD_SECT_XN | PMD_SECT_RDONLY;
> > diff --git a/arch/arm/include/asm/pgtable.h b/arch/arm/include/asm/pgtable.h
> > index 767aa7c..2d96381 100644
> > --- a/arch/arm/include/asm/pgtable.h
> > +++ b/arch/arm/include/asm/pgtable.h
> > @@ -169,11 +169,14 @@ extern pgd_t swapper_pg_dir[PTRS_PER_PGD];
> >
> >  static inline pte_t *pmd_page_vaddr(pmd_t pmd)
> >  {
> > +#ifdef SYS_SUPPORTS_HUGETLBFS
> > +       if ((pmd_val(pmd) & PMD_TYPE_MASK) == PMD_TYPE_SECT)
> > +               return __va(pmd_val(pmd) & HPAGE_MASK);
> > +#endif
> > +
> >         return __va(pmd_val(pmd) & PHYS_MASK & (s32)PAGE_MASK);
> >  }
> >
> > -#define pmd_page(pmd)          pfn_to_page(__phys_to_pfn(pmd_val(pmd) & PHYS_MASK))
> > -
> >  #ifndef CONFIG_HIGHPTE
> >  #define __pte_map(pmd)         pmd_page_vaddr(*(pmd))
> >  #define __pte_unmap(pte)       do { } while (0)
> > --
> > 1.7.9.5
> >
> The whole series looks functionally correct to me:
> 
> Reviewed-by: Christoffer Dall <c.dall@virtualopensystems.com>
> 

A big thank you for going through this Christoffer.

I'm correcting/simplifying/testing the huge pages code and will send out another
version soon.

Cheers,
-- 
Steve