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

On Tue, 2019-08-20 at 13:16 +0200, Thomas Gleixner wrote:

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?

Won't that keep returning the same address forever if addr & PUD_MASK == 0?