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

[Steven Price <steven.price@arm.com>]

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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