Re: [PATCH 6/9] mm: convert PTE table entry to pte

["David Hildenbrand (Arm)" <david@xxxxxxxxxx>]

On 8/10/26 13:06, Muhammad Usama Anjum wrote:
> On 10/08/2026 7:44 am, Alexander Gordeev wrote:
>> On Fri, Aug 07, 2026 at 05:26:04PM +0100, Muhammad Usama Anjum wrote:
>>> Yes, this is particular line is for non MMU. In this case, 
>>> CONIFG_ARCH_HAS_HW_PTE
>>> would never be defined. Hence hw_pte_t is just pte_t and direct dereference 
>>> is
>>> allowed. I'd thought a lot about it; is better to leave direct dereference 
>>> here
>>> or use some helper. Then used __pte_from_hw() was already being used in 
>>> generic
>>> ptep_get().
>>
>> But in case CONIFG_ARCH_HAS_HW_PTE=n __pte_from_hw() is still gets called.
>> That looks inconsistent to me. Why not just call ptep_deref() (see below)?
> 
> Agreed. Calling __pte_from_hw() directly exposes the representation
> conversion at the call site. I will introduce ptep_deref() and use it
> here.
> 
>>
>>> There are only two users of __pte_from_hw() at this time. 
>>>
>>> ptep_get_sw() or ptep_get_deref() is better name here?
>>
>> ptep_deref() would be it.
>>
>> Do you agree to the suggested API requirements?
> 
> Yes. hw_pte_t * identifies storage containing hardware-formatted PTEs,
> regardless of whether it is attached. ptep_get() is used for attached
> entries and may provide additional architecture-specific handling.
> ptep_deref() is used for unattached entries and performs only the raw
> storage-to-value conversion.
> 
> For review, this patch would become:
> 
> diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
> index bc0b9c65aa1d0..ce900d2652d91 100644
> --- a/include/linux/hugetlb.h
> +++ b/include/linux/hugetlb.h
> @@ -1283,7 +1283,7 @@ static inline pte_t huge_ptep_clear_flush(struct 
> vm_area_struct *vma,
>  #ifdef CONFIG_MMU
>       return ptep_get(ptep);
>  #else
> -     return *ptep;
> +     return ptep_deref(ptep);
>  #endif
>  }
>  
> diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
> index 1768421755a9c..08613593f3320 100644
> --- a/include/linux/pgtable.h
> +++ b/include/linux/pgtable.h
> @@ -490,6 +490,13 @@ static inline int pudp_set_access_flags(struct 
> vm_area_struct *vma,
>  #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
>  #endif
>  
> +#ifndef ptep_deref
> +static inline pte_t ptep_deref(hw_pte_t *ptep)
> +{
> +     return __pte_from_hw(*ptep);
> +}
> +#endif
> +
>  #ifndef ptep_get
>  static inline pte_t ptep_get(hw_pte_t *ptep)
>  {
> 

I mean, how many such users do we expect? 1? :)

Why have a helper for that then, that seems to encourage it's use, when really
people should be using ptep_get() ?

-- 
Cheers,

David