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From:   Paul Burton <paul.burton@mips.com>
To:     Steven Price <steven.price@arm.com>
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Subject: Re: [PATCH v9 04/21] mips: mm: Add p?d_leaf() definitions
Thread-Topic: [PATCH v9 04/21] mips: mm: Add p?d_leaf() definitions
Thread-Index: AQHVQKQWHhmeZU4KlE2qPPJZI7g5vqbXLM0A
Date:   Mon, 22 Jul 2019 21:47:24 +0000
Message-ID: <20190722214722.wdlj6a3der3r2oro@pburton-laptop>
References: <20190722154210.42799-1-steven.price@arm.com>
 <20190722154210.42799-5-steven.price@arm.com>
In-Reply-To: <20190722154210.42799-5-steven.price@arm.com>
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Hi Steven,

On Mon, Jul 22, 2019 at 04:41:53PM +0100, Steven Price wrote:
> 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.
>=20
> For mips, we only support large pages on 64 bit.

That ceases to be true with commit 35476311e529 ("MIPS: Add partial
32-bit huge page support") in mips-next, so I think it may be best to
move the definition to asm/pgtable.h so that both 32b & 64b kernels can
pick it up.

Thanks,
    Paul

> For 64 bit if _PAGE_HUGE is defined we can simply look for it. When not
> defined we can be confident that there are no leaf pages in existence
> and fall back on the generic implementation (added in a later patch)
> which returns 0.
>=20
> CC: Ralf Baechle <ralf@linux-mips.org>
> CC: Paul Burton <paul.burton@mips.com>
> CC: James Hogan <jhogan@kernel.org>
> CC: linux-mips@vger.kernel.org
> Signed-off-by: Steven Price <steven.price@arm.com>
> ---
>  arch/mips/include/asm/pgtable-64.h | 8 ++++++++
>  1 file changed, 8 insertions(+)
>=20
> diff --git a/arch/mips/include/asm/pgtable-64.h b/arch/mips/include/asm/p=
gtable-64.h
> index 93a9dce31f25..2bdbf8652b5f 100644
> --- a/arch/mips/include/asm/pgtable-64.h
> +++ b/arch/mips/include/asm/pgtable-64.h
> @@ -273,6 +273,10 @@ static inline int pmd_present(pmd_t pmd)
>  	return pmd_val(pmd) !=3D (unsigned long) invalid_pte_table;
>  }
> =20
> +#ifdef _PAGE_HUGE
> +#define pmd_leaf(pmd)	((pmd_val(pmd) & _PAGE_HUGE) !=3D 0)
> +#endif
> +
>  static inline void pmd_clear(pmd_t *pmdp)
>  {
>  	pmd_val(*pmdp) =3D ((unsigned long) invalid_pte_table);
> @@ -297,6 +301,10 @@ static inline int pud_present(pud_t pud)
>  	return pud_val(pud) !=3D (unsigned long) invalid_pmd_table;
>  }
> =20
> +#ifdef _PAGE_HUGE
> +#define pud_leaf(pud)	((pud_val(pud) & _PAGE_HUGE) !=3D 0)
> +#endif
> +
>  static inline void pud_clear(pud_t *pudp)
>  {
>  	pud_val(*pudp) =3D ((unsigned long) invalid_pmd_table);
> --=20
> 2.20.1
>=20