Re: [PATCH v2 2/6] arm64: use hw_pte_val for HW PTE atomics

[Ryan Roberts]

On 22/09/2026 18:31, Muhammad Usama Anjum wrote:
> The low-level atomic PTE update paths take the address of
> pte_val(*ptep). That assumes HW PTE storage can be passed directly to
> the SW PTE value accessor and no longer type-checks when hw_pte_t is
> distinct.
> 
> Use hw_pte_val() for the lvalues passed to compare-exchange and exchange
> operations. The atomic operations and their ordering are unchanged.
> 
> Signed-off-by: Muhammad Usama Anjum <usama.anjum@xxxxxxx>

Reviewed-by: Ryan Roberts <ryan.roberts@xxxxxxx>

> ---
> Chagnes in v2:
> - Remove comment change
> - Move hw_pte_val() to generic series
> ---
>  arch/arm64/include/asm/pgtable.h | 10 +++++-----
>  arch/arm64/mm/fault.c            |  2 +-
>  2 files changed, 6 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
> index 652ce413be389..4768ec59de555 100644
> --- a/arch/arm64/include/asm/pgtable.h
> +++ b/arch/arm64/include/asm/pgtable.h
> @@ -1303,7 +1303,7 @@ static inline bool __ptep_test_and_clear_young(struct vm_area_struct *vma,
>  	do {
>  		old_pte = pte;
>  		pte = pte_mkold(pte);
> -		pte_val(pte) = cmpxchg_relaxed(&pte_val(*ptep),
> +		pte_val(pte) = cmpxchg_relaxed(&hw_pte_val(*ptep),
>  					       pte_val(old_pte), pte_val(pte));
>  	} while (pte_val(pte) != pte_val(old_pte));
>  
> @@ -1346,7 +1346,7 @@ static inline pte_t __ptep_get_and_clear_anysz(struct mm_struct *mm,
>  					       hw_pte_t *ptep,
>  					       unsigned long pgsize)
>  {
> -	pte_t pte = __pte(xchg_relaxed(&pte_val(*ptep), 0));
> +	pte_t pte = __pte(xchg_relaxed(&hw_pte_val(*ptep), 0));
>  
>  	switch (pgsize) {
>  	case PAGE_SIZE:
> @@ -1422,7 +1422,7 @@ static inline void ___ptep_set_wrprotect(struct mm_struct *mm,
>  	do {
>  		old_pte = pte;
>  		pte = pte_wrprotect(pte);
> -		pte_val(pte) = cmpxchg_relaxed(&pte_val(*ptep),
> +		pte_val(pte) = cmpxchg_relaxed(&hw_pte_val(*ptep),
>  					       pte_val(old_pte), pte_val(pte));
>  	} while (pte_val(pte) != pte_val(old_pte));
>  }
> @@ -1460,7 +1460,7 @@ static inline void __clear_young_dirty_pte(struct vm_area_struct *vma,
>  		if (flags & CYDP_CLEAR_DIRTY)
>  			pte = pte_mkclean(pte);
>  
> -		pte_val(pte) = cmpxchg_relaxed(&pte_val(*ptep),
> +		pte_val(pte) = cmpxchg_relaxed(&hw_pte_val(*ptep),
>  					       pte_val(old_pte), pte_val(pte));
>  	} while (pte_val(pte) != pte_val(old_pte));
>  }
> @@ -1830,7 +1830,7 @@ static inline bool ptep_try_set(hw_pte_t *ptep, pte_t new_pte)
>  {
>  	pteval_t old = 0;
>  
> -	if (!try_cmpxchg(&pte_val(*ptep), &old, pte_val(new_pte)))
> +	if (!try_cmpxchg(&hw_pte_val(*ptep), &old, pte_val(new_pte)))
>  		return false;
>  
>  	/*
> diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
> index b77f4be88e3ea..3322f4e7174dc 100644
> --- a/arch/arm64/mm/fault.c
> +++ b/arch/arm64/mm/fault.c
> @@ -235,7 +235,7 @@ int __ptep_set_access_flags_anysz(struct vm_area_struct *vma,
>  		pteval ^= PTE_RDONLY;
>  		pteval |= pte_val(entry);
>  		pteval ^= PTE_RDONLY;
> -		pteval = cmpxchg_relaxed(&pte_val(*ptep), old_pteval, pteval);
> +		pteval = cmpxchg_relaxed(&hw_pte_val(*ptep), old_pteval, pteval);
>  	} while (pteval != old_pteval);
>  
>  	/*
>