Re: [PATCH] x86/mm/pti: in pti_clone_pgtable() don't increase addr by PUD_SIZE

Thomas Gleixner
2019-08-20T11:16:48Z

On Tue, 20 Aug 2019, Peter Zijlstra wrote:
> What that code wants to do is skip to the end of the pud, a pmd_size
> increase will not do that. And right below this, there's a second
> instance of this exact pattern.
>
> Did I get the below right?
>
> ---
> diff --git a/arch/x86/mm/pti.c b/arch/x86/mm/pti.c
> index b196524759ec..32b20b3cb227 100644
> --- a/arch/x86/mm/pti.c
> +++ b/arch/x86/mm/pti.c
> @@ -330,12 +330,14 @@ pti_clone_pgtable(unsigned long start, unsigned long end,
>
> pud = pud_offset(p4d, addr);
> if (pud_none(*pud)) {
> + addr &= PUD_MASK;
> addr += PUD_SIZE;

round_up(addr, PUD_SIZE);

perhaps?

> continue;
> }
>
> pmd = pmd_offset(pud, addr);
> if (pmd_none(*pmd)) {
> + addr &= PMD_MASK;
> addr += PMD_SIZE;
> continue;
> }
>