quoted

  #ifndef pte_batch_hint

diff --git a/mm/kasan/shadow.c b/mm/kasan/shadow.c
index 5d2a876035d6..c49b029d3593 100644
--- a/mm/kasan/shadow.c
+++ b/mm/kasan/shadow.c

@@ -305,7 +305,7 @@ static int kasan_populate_vmalloc_pte(pte_t *ptep, unsigned long addr,
  	pte_t pte;
  	int index;
  
-	arch_leave_lazy_mmu_mode();
+	lazy_mmu_mode_pause();

I wonder if there really are use cases that *require* pause/resume? I think
these kasan cases could be correctly implemented using a new nest level instead?
Are there cases where the effects really need to be immediate or do the effects
just need to be visible when you get to where the resume is?

If the latter, that could just be turned into a nested disable (e.g. a flush).
In this case, there is only 1 PTE write so no benefit, but I wonder if other
cases may have more PTE writes that could then still be batched. It would be
nice to simplify the API by removing pause/resume if we can?

It has clear semantics, clearer than some nest-disable IMHO.

Maybe you can elaborate how you would change ("simplify") the API in 
that regard? What would the API look like?