On 05/29/2017 06:32 PM, David Hildenbrand wrote:

>       new = old = pgste_get_lock(ptep);
>       pgste_val(new) &= ~(PGSTE_GR_BIT | PGSTE_GC_BIT |
> @@ -748,6 +764,11 @@ int reset_guest_reference_bit(struct mm_struct *mm, 
> unsigned long addr)
>       ptep = get_locked_pte(mm, addr, &ptl);
>       if (unlikely(!ptep))
>               return -EFAULT;
> +     if (!pgtable_has_pgste(mm, __pa(ptep))) {
> +             pte_unmap_unlock(ptep, ptl);
> +             WARN_ONCE(true, "Guest address on page table without pgste");

All these WARN_ONCE. Is there a way how a malicious user can trigger this or is 
this checked
everywhere and triggered would be indeed a bug?

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