[PATCH v7 2/7] arm64/vmalloc: Allow arch_vmap_pte_range_map_size to batch multiple CONT_PTE

[Barry Song]

On Wed, Jul 22, 2026 at 2:17 AM David Carlier <devnexen at gmail.com> wrote:
>
> Barry, Wen - the returned span is capped at PMD_SIZE >> 1 but only
> checked for CONT_PTE_SIZE alignment. In the batched vmap() path pages
> are only contiguous within a naturally aligned block, so when a PMD
> boundary splits a batch the next region starts mid block and the span
> runs past the contiguous run - set_huge_pte_at() maps the wrong pages,
> tail of the array left unmapped, no warning.
>
> What do you think of clamping the span to the pfn physical alignment,
> like 8xx does:
>
>         while (!IS_ALIGNED(PFN_PHYS(pfn), size))
>                 size >>= 1;

Thanks, David.

I noticed that 8xx has simplified this to a simple

    if (!IS_ALIGNED(PFN_PHYS(pfn), size))

Could we do the same here?

diff --git a/arch/arm64/include/asm/vmalloc.h b/arch/arm64/include/asm/vmalloc.h
index d665f9d68742..a27101e24f76 100644
--- a/arch/arm64/include/asm/vmalloc.h
+++ b/arch/arm64/include/asm/vmalloc.h
@@ -46,6 +46,8 @@ static inline unsigned long
arch_vmap_pte_range_map_size(unsigned long addr,

        size = min3(end - addr, 1UL << max_page_shift, PMD_SIZE >> 1);
        size = rounddown_pow_of_two(size);
+       if (!IS_ALIGNED(PFN_PHYS(pfn), size) || size < CONT_PTE_SIZE)
+               return PAGE_SIZE;
        return size;
 }

>
> Cheers.