linux-kernel - Re: [PATCH v16 06/25] powerpc: mm: Add p?d

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Date:   Mon, 09 Dec 2019 22:08:32 +1100
From:   Michael Ellerman <mpe@...erman.id.au>
To:     Steven Price <steven.price@....com>,
        Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org
Cc:     Steven Price <steven.price@....com>,
        Andy Lutomirski <luto@...nel.org>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Arnd Bergmann <arnd@...db.de>, Borislav Petkov <bp@...en8.de>,
        Catalin Marinas <catalin.marinas@....com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Ingo Molnar <mingo@...hat.com>,
        James Morse <james.morse@....com>,
        Jérôme Glisse <jglisse@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Will Deacon <will@...nel.org>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Mark Rutland <Mark.Rutland@....com>,
        "Liang\, Kan" <kan.liang@...ux.intel.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        linuxppc-dev@...ts.ozlabs.org, kvm-ppc@...r.kernel.org
Subject: Re: [PATCH v16 06/25] powerpc: mm: Add p?d_leaf() definitions

Steven Price <steven.price@....com> writes:
> walk_page_range() is going to be allowed to walk page tables other than
> those of user space. For this it needs to know when it has reached a
> 'leaf' entry in the page tables. This information is provided by the
> p?d_leaf() functions/macros.
>
> For powerpc pmd_large() already exists and does what we want, so hoist
> it out of the CONFIG_TRANSPARENT_HUGEPAGE condition and implement the
> other levels. Macros are used to provide the generic p?d_leaf() names.
>
> CC: Benjamin Herrenschmidt <benh@...nel.crashing.org>
> CC: Paul Mackerras <paulus@...ba.org>
> CC: Michael Ellerman <mpe@...erman.id.au>
> CC: linuxppc-dev@...ts.ozlabs.org
> CC: kvm-ppc@...r.kernel.org
> Signed-off-by: Steven Price <steven.price@....com>
> ---
>  arch/powerpc/include/asm/book3s/64/pgtable.h | 30 ++++++++++++++------
>  1 file changed, 21 insertions(+), 9 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/book3s/64/pgtable.h b/arch/powerpc/include/asm/book3s/64/pgtable.h
> index b01624e5c467..3dd7b6f5edd0 100644
> --- a/arch/powerpc/include/asm/book3s/64/pgtable.h
> +++ b/arch/powerpc/include/asm/book3s/64/pgtable.h
> @@ -923,6 +923,12 @@ static inline int pud_present(pud_t pud)
>  	return !!(pud_raw(pud) & cpu_to_be64(_PAGE_PRESENT));
>  }
>  
> +#define pud_leaf	pud_large
> +static inline int pud_large(pud_t pud)
> +{
> +	return !!(pud_raw(pud) & cpu_to_be64(_PAGE_PTE));
> +}

We already have:

#define pud_is_leaf pud_is_leaf
static inline bool pud_is_leaf(pud_t pud)
{
	return !!(pud_raw(pud) & cpu_to_be64(_PAGE_PTE));
}

And so on.

These went in relatively recently in:

  d6eacedd1f0e ("powerpc/book3s: Use config independent helpers for page table walk")


Assuming those all work for you, maybe your patch in this series should
just do:

#define pud_leaf pud_is_leaf

And so on. And then we can do a patch later to change the arch/powerpc
code to use pud_leaf() etc. directly and drop the "is" versions.

cheers


> @@ -966,6 +972,12 @@ static inline int pgd_present(pgd_t pgd)
>  	return !!(pgd_raw(pgd) & cpu_to_be64(_PAGE_PRESENT));
>  }
>  
> +#define pgd_leaf	pgd_large
> +static inline int pgd_large(pgd_t pgd)
> +{
> +	return !!(pgd_raw(pgd) & cpu_to_be64(_PAGE_PTE));
> +}
> +
>  static inline pte_t pgd_pte(pgd_t pgd)
>  {
>  	return __pte_raw(pgd_raw(pgd));
> @@ -1133,6 +1145,15 @@ static inline bool pmd_access_permitted(pmd_t pmd, bool write)
>  	return pte_access_permitted(pmd_pte(pmd), write);
>  }
>  
> +#define pmd_leaf	pmd_large
> +/*
> + * returns true for pmd migration entries, THP, devmap, hugetlb
> + */
> +static inline int pmd_large(pmd_t pmd)
> +{
> +	return !!(pmd_raw(pmd) & cpu_to_be64(_PAGE_PTE));
> +}
> +
>  #ifdef CONFIG_TRANSPARENT_HUGEPAGE
>  extern pmd_t pfn_pmd(unsigned long pfn, pgprot_t pgprot);
>  extern pmd_t mk_pmd(struct page *page, pgprot_t pgprot);
> @@ -1159,15 +1180,6 @@ pmd_hugepage_update(struct mm_struct *mm, unsigned long addr, pmd_t *pmdp,
>  	return hash__pmd_hugepage_update(mm, addr, pmdp, clr, set);
>  }
>  
> -/*
> - * returns true for pmd migration entries, THP, devmap, hugetlb
> - * But compile time dependent on THP config
> - */
> -static inline int pmd_large(pmd_t pmd)
> -{
> -	return !!(pmd_raw(pmd) & cpu_to_be64(_PAGE_PTE));
> -}
> -
>  static inline pmd_t pmd_mknotpresent(pmd_t pmd)
>  {
>  	return __pmd(pmd_val(pmd) & ~_PAGE_PRESENT);
> -- 
> 2.20.1