On 23.01.24 12:38, Ryan Roberts wrote:

On 23/01/2024 11:31, David Hildenbrand wrote:

quoted

quoted

quoted

quoted

If high bits are used for
something else, then we might produce a garbage PTE on overflow, but that
shouldn't really matter I concluded for folio_pte_batch() purposes, we'd not
detect "belongs to this folio batch" either way.

Exactly.

quoted

Maybe it's likely cleaner to also have a custom pte_next_pfn() on ppc, I just
hope that we don't lose any other arbitrary PTE bits by doing the pte_pgprot().

I don't see the need for ppc to implement pte_next_pfn().

Agreed.

So likely we should then do on top for powerpc (whitespace damage):

diff --git a/arch/powerpc/mm/pgtable.c b/arch/powerpc/mm/pgtable.c
index a04ae4449a025..549a440ed7f65 100644
--- a/arch/powerpc/mm/pgtable.c
+++ b/arch/powerpc/mm/pgtable.c

@@ -220,10 +220,7 @@ void set_ptes(struct mm_struct *mm, unsigned long addr,

pte_t *ptep,
                         break;
                 ptep++;
                 addr += PAGE_SIZE;
-               /*
-                * increment the pfn.
-                */
-               pte = pfn_pte(pte_pfn(pte) + 1, pte_pgprot((pte)));
+               pte = pte_next_pfn(pte);
         }
  }

Looks like commit 47b8def9358c ("powerpc/mm: Avoid calling
arch_enter/leave_lazy_mmu() in set_ptes") changed from doing the simple
increment to this more complex approach, but the log doesn't say why.

@Aneesh, was that change on purpose?

-- 
Cheers,

David / dhildenb


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