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

[Christophe Leroy <christophe.leroy@csgroup.eu>]

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 ?

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().
- 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 */