[PATCH v9 04/21] mips: mm: Add p?d_leaf() definitions

[PATCH v9 04/21] mips: mm: Add p?d_leaf() definitions

[Steven Price]

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 mips, we only support large pages on 64 bit.

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.

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(+)

diff --git a/arch/mips/include/asm/pgtable-64.h b/arch/mips/include/asm/pgtable-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) != (unsigned long) invalid_pte_table;
 }
 
+#ifdef _PAGE_HUGE
+#define pmd_leaf(pmd)	((pmd_val(pmd) & _PAGE_HUGE) != 0)
+#endif
+
 static inline void pmd_clear(pmd_t *pmdp)
 {
 	pmd_val(*pmdp) = ((unsigned long) invalid_pte_table);
@@ -297,6 +301,10 @@ static inline int pud_present(pud_t pud)
 	return pud_val(pud) != (unsigned long) invalid_pmd_table;
 }
 
+#ifdef _PAGE_HUGE
+#define pud_leaf(pud)	((pud_val(pud) & _PAGE_HUGE) != 0)
+#endif
+
 static inline void pud_clear(pud_t *pudp)
 {
 	pud_val(*pudp) = ((unsigned long) invalid_pmd_table);
-- 
2.20.1

Re: [PATCH v9 04/21] mips: mm: Add p?d_leaf() definitions

[Paul Burton]

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.
> 
> 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.
> 
> 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(+)
> 
> diff --git a/arch/mips/include/asm/pgtable-64.h b/arch/mips/include/asm/pgtable-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) != (unsigned long) invalid_pte_table;
>  }
>  
> +#ifdef _PAGE_HUGE
> +#define pmd_leaf(pmd)	((pmd_val(pmd) & _PAGE_HUGE) != 0)
> +#endif
> +
>  static inline void pmd_clear(pmd_t *pmdp)
>  {
>  	pmd_val(*pmdp) = ((unsigned long) invalid_pte_table);
> @@ -297,6 +301,10 @@ static inline int pud_present(pud_t pud)
>  	return pud_val(pud) != (unsigned long) invalid_pmd_table;
>  }
>  
> +#ifdef _PAGE_HUGE
> +#define pud_leaf(pud)	((pud_val(pud) & _PAGE_HUGE) != 0)
> +#endif
> +
>  static inline void pud_clear(pud_t *pudp)
>  {
>  	pud_val(*pudp) = ((unsigned long) invalid_pmd_table);
> -- 
> 2.20.1
> 

Re: [PATCH v9 04/21] mips: mm: Add p?d_leaf() definitions

[Steven Price]

On 22/07/2019 22:47, Paul Burton wrote:
> 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.
>>
>> 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 for pointing that out. I'll move the definitions as you suggest.

Steve

> 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.
>>
>> 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(+)
>>
>> diff --git a/arch/mips/include/asm/pgtable-64.h b/arch/mips/include/asm/pgtable-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) != (unsigned long) invalid_pte_table;
>>  }
>>  
>> +#ifdef _PAGE_HUGE
>> +#define pmd_leaf(pmd)	((pmd_val(pmd) & _PAGE_HUGE) != 0)
>> +#endif
>> +
>>  static inline void pmd_clear(pmd_t *pmdp)
>>  {
>>  	pmd_val(*pmdp) = ((unsigned long) invalid_pte_table);
>> @@ -297,6 +301,10 @@ static inline int pud_present(pud_t pud)
>>  	return pud_val(pud) != (unsigned long) invalid_pmd_table;
>>  }
>>  
>> +#ifdef _PAGE_HUGE
>> +#define pud_leaf(pud)	((pud_val(pud) & _PAGE_HUGE) != 0)
>> +#endif
>> +
>>  static inline void pud_clear(pud_t *pudp)
>>  {
>>  	pud_val(*pudp) = ((unsigned long) invalid_pmd_table);
>> -- 
>> 2.20.1
>>
> 
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