Re: [PATCH v9 4/7] powerpc: mm: Default p{m,u}d_pte implementations

[Rohan McLure <rmclure@linux.ibm.com>]

On 11/30/23 18:35, Christophe Leroy wrote:
>
> Le 30/11/2023 à 03:53, Rohan McLure a écrit :
>> For 32-bit systems which have no usecases for p{m,u}d_pte() prior to
>> page table checking, implement default stubs.
> Is that the best solution ?
>
> If I understand correctly, it is only needed for 
> pmd_user_accessible_page(). Why not provide a stub 
> pmd_user_accessible_page() that returns false on those architectures ?
Yep, this seems reasonable to me.
>
> Same for pud_user_accessible_page()
>
> But if you decide to keep it I think that:
> - It should be squashed with following patch to make it clear it's 
> needed for that only.
> - Remove the WARN_ONCE().
I might however move those WARN_ONCE() calls to the default, false-returning
p{m,u}d_user_accessible_page() implementations, to be consistent with
pud_pfn().
> - Only have a special one for books/64 and a generic only common to he 3 
> others.
>
>> Signed-off-by: Rohan McLure <rmclure@linux.ibm.com>
>> ---
>> v9: New patch
>> ---
>>   arch/powerpc/include/asm/book3s/64/pgtable.h |  3 +++
>>   arch/powerpc/include/asm/nohash/64/pgtable.h |  2 ++
>>   arch/powerpc/include/asm/pgtable.h           | 17 +++++++++++++++++
>>   3 files changed, 22 insertions(+)
>>
>> diff --git a/arch/powerpc/include/asm/book3s/64/pgtable.h b/arch/powerpc/include/asm/book3s/64/pgtable.h
>> index 8fdb7667c509..2454174b26cb 100644
>> --- a/arch/powerpc/include/asm/book3s/64/pgtable.h
>> +++ b/arch/powerpc/include/asm/book3s/64/pgtable.h
>> @@ -887,6 +887,8 @@ static inline int pud_present(pud_t pud)
>>   
>>   extern struct page *pud_page(pud_t pud);
>>   extern struct page *pmd_page(pmd_t pmd);
>> +
>> +#define pud_pte pud_pte
>>   static inline pte_t pud_pte(pud_t pud)
>>   {
>>   	return __pte_raw(pud_raw(pud));
>> @@ -1043,6 +1045,7 @@ static inline void __kernel_map_pages(struct page *page, int numpages, int enabl
>>   }
>>   #endif
>>   
>> +#define pmd_pte pmd_pte
>>   static inline pte_t pmd_pte(pmd_t pmd)
>>   {
>>   	return __pte_raw(pmd_raw(pmd));
>> diff --git a/arch/powerpc/include/asm/nohash/64/pgtable.h b/arch/powerpc/include/asm/nohash/64/pgtable.h
>> index f58cbebde26e..09a34fe196ae 100644
>> --- a/arch/powerpc/include/asm/nohash/64/pgtable.h
>> +++ b/arch/powerpc/include/asm/nohash/64/pgtable.h
>> @@ -93,6 +93,7 @@ static inline void pmd_clear(pmd_t *pmdp)
>>   	*pmdp = __pmd(0);
>>   }
>>   
>> +#define pmd_pte pmd_pte
>>   static inline pte_t pmd_pte(pmd_t pmd)
>>   {
>>   	return __pte(pmd_val(pmd));
>> @@ -134,6 +135,7 @@ static inline pmd_t *pud_pgtable(pud_t pud)
>>   
>>   extern struct page *pud_page(pud_t pud);
>>   
>> +#define pud_pte pud_pte
>>   static inline pte_t pud_pte(pud_t pud)
>>   {
>>   	return __pte(pud_val(pud));
>> diff --git a/arch/powerpc/include/asm/pgtable.h b/arch/powerpc/include/asm/pgtable.h
>> index 9c0f2151f08f..d7d0f47760d3 100644
>> --- a/arch/powerpc/include/asm/pgtable.h
>> +++ b/arch/powerpc/include/asm/pgtable.h
>> @@ -233,6 +233,23 @@ static inline int pud_pfn(pud_t pud)
>>   }
>>   #endif
>>   
>> +#ifndef pmd_pte
>> +#define pmd_pte pmd_pte
>> +static inline pte_t pmd_pte(pmd_t pmd)
>> +{
>> +	WARN_ONCE(1, "pmd: platform does not use pmd entries directly");
>> +	return __pte(pmd_val(pmd));
>> +}
>> +#endif
>> +
>> +#ifndef pud_pte
>> +#define pud_pte pud_pte
>> +static inline pte_t pud_pte(pud_t pud)
>> +{
>> +	WARN_ONCE(1, "pud: platform does not use pud entries directly");
>> +	return __pte(pud_val(pud));
>> +}
>> +#endif
>>   #endif /* __ASSEMBLY__ */
>>   
>>   #endif /* _ASM_POWERPC_PGTABLE_H */