Re: [PATCH mm-unstable RFC v4 2/7] arm64/mm: use PTE-level pgprot for huge PFN helpers

[Will Deacon]

On Tue, May 26, 2026 at 10:49:58PM +0800, Yin Tirui wrote:
> Make the arm64 PMD/PUD PFN helpers use PTE-level pgprot_t as the basic
> format.
> 
> pfn_pmd() and pfn_pud() now translate PTE-level attributes into block
> entries. pmd_pgprot() and pud_pgprot() translate block descriptor
> attributes back into PTE-level attributes.
> 
> Remove mk_pmd_sect_prot() and mk_pud_sect_prot().
> 
> Signed-off-by: Yin Tirui <yintirui@xxxxxxxxxx>
> ---
>  arch/arm64/include/asm/pgtable.h | 48 ++++++++++++++++++++++----------
>  arch/arm64/mm/mmu.c              |  4 +--
>  2 files changed, 36 insertions(+), 16 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
> index 4dfa42b7d053..c3ee12e14f86 100644
> --- a/arch/arm64/include/asm/pgtable.h
> +++ b/arch/arm64/include/asm/pgtable.h
> @@ -511,16 +511,6 @@ static inline pmd_t pte_pmd(pte_t pte)
>  	return __pmd(pte_val(pte));
>  }
>  
> -static inline pgprot_t mk_pud_sect_prot(pgprot_t prot)
> -{
> -	return __pgprot((pgprot_val(prot) & ~PUD_TYPE_MASK) | PUD_TYPE_SECT);
> -}
> -
> -static inline pgprot_t mk_pmd_sect_prot(pgprot_t prot)
> -{
> -	return __pgprot((pgprot_val(prot) & ~PMD_TYPE_MASK) | PMD_TYPE_SECT);
> -}
> -
>  static inline pte_t pte_swp_mkexclusive(pte_t pte)
>  {
>  	return set_pte_bit(pte, __pgprot(PTE_SWP_EXCLUSIVE));
> @@ -628,7 +618,13 @@ static inline pmd_t pmd_mkspecial(pmd_t pmd)
>  #define __pmd_to_phys(pmd)	__pte_to_phys(pmd_pte(pmd))
>  #define __phys_to_pmd_val(phys)	__phys_to_pte_val(phys)
>  #define pmd_pfn(pmd)		((__pmd_to_phys(pmd) & PMD_MASK) >> PAGE_SHIFT)
> -#define pfn_pmd(pfn,prot)	__pmd(__phys_to_pmd_val((phys_addr_t)(pfn) << PAGE_SHIFT) | pgprot_val(prot))
> +static inline pmd_t pfn_pmd(unsigned long pfn, pgprot_t prot)
> +{
> +	pmd_t pmd = __pmd(__phys_to_pmd_val((phys_addr_t)pfn << PAGE_SHIFT) |
> +			  pgprot_val(prot));
> +
> +	return pmd_mkhuge(pmd);
> +}

There's a slight potential difference in behaviour here, in that the old
mk_pXd_sect_prot() helpers would always return a pgprot_t with the valid
bit set, whereas pXd_mkhuge() preserve it from the input prot.

I couldn't find any places that cared about this, though, so:

Acked-by: Will Deacon <will@xxxxxxxxxx>

Will