Re: [PATCH v3 02/13] powerpc/mm: Move setting pte specific flags to pfn_pte

[Anshuman Khandual <anshuman.khandual@arm.com>]

On 08/27/2020 01:34 PM, Aneesh Kumar K.V wrote:
> powerpc used to set the pte specific flags in set_pte_at(). This is different
> from other architectures. To be consistent with other architecture update
> pfn_pte to set _PAGE_PTE on ppc64. Also, drop now unused pte_mkpte.
> 
> We add a VM_WARN_ON() to catch the usage of calling set_pte_at() without setting
> _PAGE_PTE bit. We will remove that after a few releases.
> 
> With respect to huge pmd entries, pmd_mkhuge() takes care of adding the
> _PAGE_PTE bit.
> 
> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
> ---
>  arch/powerpc/include/asm/book3s/64/pgtable.h | 15 +++++++++------
>  arch/powerpc/include/asm/nohash/pgtable.h    |  5 -----
>  arch/powerpc/mm/pgtable.c                    |  5 -----
>  3 files changed, 9 insertions(+), 16 deletions(-)
> 
> diff --git a/arch/powerpc/include/asm/book3s/64/pgtable.h b/arch/powerpc/include/asm/book3s/64/pgtable.h
> index 079211968987..2382fd516f6b 100644
> --- a/arch/powerpc/include/asm/book3s/64/pgtable.h
> +++ b/arch/powerpc/include/asm/book3s/64/pgtable.h
> @@ -619,7 +619,7 @@ static inline pte_t pfn_pte(unsigned long pfn, pgprot_t pgprot)
>  	VM_BUG_ON(pfn >> (64 - PAGE_SHIFT));
>  	VM_BUG_ON((pfn << PAGE_SHIFT) & ~PTE_RPN_MASK);
>  
> -	return __pte(((pte_basic_t)pfn << PAGE_SHIFT) | pgprot_val(pgprot));
> +	return __pte(((pte_basic_t)pfn << PAGE_SHIFT) | pgprot_val(pgprot) | _PAGE_PTE);
>  }
>  
>  static inline unsigned long pte_pfn(pte_t pte)
> @@ -655,11 +655,6 @@ static inline pte_t pte_mkexec(pte_t pte)
>  	return __pte_raw(pte_raw(pte) | cpu_to_be64(_PAGE_EXEC));
>  }
>  
> -static inline pte_t pte_mkpte(pte_t pte)
> -{
> -	return __pte_raw(pte_raw(pte) | cpu_to_be64(_PAGE_PTE));
> -}
> -
>  static inline pte_t pte_mkwrite(pte_t pte)
>  {
>  	/*
> @@ -823,6 +818,14 @@ static inline int pte_none(pte_t pte)
>  static inline void __set_pte_at(struct mm_struct *mm, unsigned long addr,
>  				pte_t *ptep, pte_t pte, int percpu)
>  {
> +
> +	VM_WARN_ON(!(pte_raw(pte) & cpu_to_be64(_PAGE_PTE)));
> +	/*
> +	 * Keep the _PAGE_PTE added till we are sure we handle _PAGE_PTE
> +	 * in all the callers.
> +	 */
> +	 pte = __pte_raw(pte_raw(pte) | cpu_to_be64(_PAGE_PTE));
> +
>  	if (radix_enabled())
>  		return radix__set_pte_at(mm, addr, ptep, pte, percpu);
>  	return hash__set_pte_at(mm, addr, ptep, pte, percpu);
> diff --git a/arch/powerpc/include/asm/nohash/pgtable.h b/arch/powerpc/include/asm/nohash/pgtable.h
> index 4b7c3472eab1..6277e7596ae5 100644
> --- a/arch/powerpc/include/asm/nohash/pgtable.h
> +++ b/arch/powerpc/include/asm/nohash/pgtable.h
> @@ -140,11 +140,6 @@ static inline pte_t pte_mkold(pte_t pte)
>  	return __pte(pte_val(pte) & ~_PAGE_ACCESSED);
>  }
>  
> -static inline pte_t pte_mkpte(pte_t pte)
> -{
> -	return pte;
> -}
> -
>  static inline pte_t pte_mkspecial(pte_t pte)
>  {
>  	return __pte(pte_val(pte) | _PAGE_SPECIAL);
> diff --git a/arch/powerpc/mm/pgtable.c b/arch/powerpc/mm/pgtable.c
> index 9c0547d77af3..ab57b07ef39a 100644
> --- a/arch/powerpc/mm/pgtable.c
> +++ b/arch/powerpc/mm/pgtable.c
> @@ -184,9 +184,6 @@ void set_pte_at(struct mm_struct *mm, unsigned long addr, pte_t *ptep,
>  	 */
>  	VM_WARN_ON(pte_hw_valid(*ptep) && !pte_protnone(*ptep));
>  
> -	/* Add the pte bit when trying to set a pte */
> -	pte = pte_mkpte(pte);
> -
>  	/* Note: mm->context.id might not yet have been assigned as
>  	 * this context might not have been activated yet when this
>  	 * is called.
> @@ -275,8 +272,6 @@ void set_huge_pte_at(struct mm_struct *mm, unsigned long addr, pte_t *ptep, pte_
>  	 */
>  	VM_WARN_ON(pte_hw_valid(*ptep) && !pte_protnone(*ptep));
>  
> -	pte = pte_mkpte(pte);
> -
>  	pte = set_pte_filter(pte);
>  
>  	val = pte_val(pte);
> 

There is one checkpatch.pl warning for this patch.

WARNING: Possible unwrapped commit description (prefer a maximum 75 chars per line)
#6: 
powerpc used to set the pte specific flags in set_pte_at(). This is different

total: 0 errors, 1 warnings, 61 lines checked