[PATCH] powerpc/mm: Use pte_advance_pfn() in set_huge_pte_at()

[PATCH] powerpc/mm: Use pte_advance_pfn() in set_huge_pte_at()

[Andrew Donnellan]

In set_huge_pte_at(), replace the existing open coded pte value
calculation with the new helper pte_advance_pfn().

Signed-off-by: Andrew Donnellan <ajd@linux.ibm.com>
---
 arch/powerpc/mm/pgtable.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/powerpc/mm/pgtable.c b/arch/powerpc/mm/pgtable.c
index 56d7e8960e77d877390d6bcbf0d8a305cc222101..9073e373e1e8a88f904cae592e1e8c34707545e6 100644
--- a/arch/powerpc/mm/pgtable.c
+++ b/arch/powerpc/mm/pgtable.c
@@ -365,7 +365,7 @@ void set_huge_pte_at(struct mm_struct *mm, unsigned long addr, pte_t *ptep,
 
 	for (i = 0; i < sz / pdsize; i++, ptep++, addr += pdsize) {
 		__set_pte_at(mm, addr, ptep, pte, 0);
-		pte = __pte(pte_val(pte) + ((unsigned long long)pdsize / PAGE_SIZE << PFN_PTE_SHIFT));
+		pte = pte_advance_pfn(pte, pdsize / PAGE_SIZE);
 	}
 }
 #endif

---
base-commit: ea1013c1539270e372fc99854bc6e4d94eaeff66
change-id: 20251219-set_huge_pte_at_pte_advance_pfn-0ae18078fcca


--
Andrew Donnellan    OzLabs, ADL Canberra
ajd@linux.ibm.com   IBM Australia Limited

Re: [PATCH] powerpc/mm: Use pte_advance_pfn() in set_huge_pte_at()

[Christophe Leroy (CS GROUP)]

Hi Andrew,

Le 18/12/2025 à 17:21, Andrew Donnellan a écrit :
> In set_huge_pte_at(), replace the existing open coded pte value
> calculation with the new helper pte_advance_pfn().
> 
> Signed-off-by: Andrew Donnellan <ajd@linux.ibm.com>
> ---
>   arch/powerpc/mm/pgtable.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/powerpc/mm/pgtable.c b/arch/powerpc/mm/pgtable.c
> index 56d7e8960e77d877390d6bcbf0d8a305cc222101..9073e373e1e8a88f904cae592e1e8c34707545e6 100644
> --- a/arch/powerpc/mm/pgtable.c
> +++ b/arch/powerpc/mm/pgtable.c
> @@ -365,7 +365,7 @@ void set_huge_pte_at(struct mm_struct *mm, unsigned long addr, pte_t *ptep,
>   
>   	for (i = 0; i < sz / pdsize; i++, ptep++, addr += pdsize) {
>   		__set_pte_at(mm, addr, ptep, pte, 0);
> -		pte = __pte(pte_val(pte) + ((unsigned long long)pdsize / PAGE_SIZE << PFN_PTE_SHIFT));
> +		pte = pte_advance_pfn(pte, pdsize / PAGE_SIZE);

How can this work ?

pdsize is 4M, PAGE_SIZE is 4k so pdsize/PAGE_SIZE is 0x400.

PFN_PTE_SHIFT is 24.

0x400 << 24 is more than what an unsigned long can contain in 
pte_advance_pfn()

Christophe

>   	}
>   }
>   #endif
> 
> ---
> base-commit: ea1013c1539270e372fc99854bc6e4d94eaeff66
> change-id: 20251219-set_huge_pte_at_pte_advance_pfn-0ae18078fcca
> 
> 
> --
> Andrew Donnellan    OzLabs, ADL Canberra
> ajd@linux.ibm.com   IBM Australia Limited
> 

Re: [PATCH] powerpc/mm: Use pte_advance_pfn() in set_huge_pte_at()

[Andrew Donnellan]

On Thu, 2025-12-18 at 19:29 +0100, Christophe Leroy (CS GROUP) wrote:
> >   	for (i = 0; i < sz / pdsize; i++, ptep++, addr += pdsize) {
> >   		__set_pte_at(mm, addr, ptep, pte, 0);
> > -		pte = __pte(pte_val(pte) + ((unsigned long long)pdsize /
> > PAGE_SIZE << PFN_PTE_SHIFT));
> > +		pte = pte_advance_pfn(pte, pdsize / PAGE_SIZE);
> 
> How can this work ?
> 
> pdsize is 4M, PAGE_SIZE is 4k so pdsize/PAGE_SIZE is 0x400.
> 
> PFN_PTE_SHIFT is 24.
> 
> 0x400 << 24 is more than what an unsigned long can contain in 
> pte_advance_pfn()

Ah, in spite of the explicit unsigned long long cast that should've reminded me
otherwise, I forgot that a long isn't 64 bits on 32 bit machines.
> 



-- 
Andrew Donnellan    OzLabs, ADL Canberra
ajd@linux.ibm.com   IBM Australia Limited