Re: [PATCH] x86/mm: don't apply va_align to hugetlb mappings on AMD F15h

[Dave Hansen]

On 9/19/26 01:47, Laurent Wandrebeck wrote:
>  static unsigned long get_align_mask(struct file *filp)
>  {
> -       if (filp && is_file_hugepages(filp))
> +       if (is_file_hugepages(filp))
>                 return huge_page_mask_align(filp);
>         /* handle 32- and 64-bit case with a single conditional */
>         if (va_align.flags < 0 || !(va_align.flags & (2 - mmap_is_ia32())))

I'd just leave that hunk out for now. It's harmless to leave.

> @@ -50,9 +50,13 @@ static unsigned long get_align_mask(struct file *filp)
>   * value before calling vm_unmapped_area() or ORed directly to the
>   * address.
>   */
> -static unsigned long get_align_bits(void)
> +static unsigned long get_align_bits(struct file *filp)
>  {
> -       return va_align.bits & get_align_mask(NULL);
> +       /* hugetlb mappings must stay on the huge page boundary. */
> +       if (is_file_hugepages(filp))
> +               return 0;

I don't find that comment helpful. The function is kinda misnamed a bit
too. Maybe a comment like this?

	/*
	 * va_align.bits is smaller than the huge page size and will
	 * lead to misaligned huge pages. Ignore it for huge mappings.
	 */

> +       return va_align.bits & get_align_mask(filp);
>  }
>  
>  static int __init control_va_addr_alignment(char *str)
> @@ -157,7 +161,7 @@ arch_get_unmapped_area(struct file *filp, unsigned long addr, unsigned long len,
>         }
>         if (filp) {
>                 info.align_mask = get_align_mask(filp);
> -               info.align_offset += get_align_bits();
> +               info.align_offset += get_align_bits(filp);
>         }
>  
>         return vm_unmapped_area(&info);
> @@ -222,7 +226,7 @@ arch_get_unmapped_area_topdown(struct file *filp, unsigned long addr0,
>  
>         if (filp) {
>                 info.align_mask = get_align_mask(filp);
> -               info.align_offset += get_align_bits();
> +               info.align_offset += get_align_bits(filp);
>         }

That looks fine too. I would rather this whole mechanism die,
personally. But this is a fine, backportable fix.