Re: [PATCH 6/6] x86: Fix stray A/D bit setting into non-present PTEs

[Nadav Amit]

Dave Hansen <dave@xxxxxxxx> wrote:

> +pte_t ptep_clear_flush(struct vm_area_struct *vma, unsigned long address,
> +		       pte_t *ptep)
> +{
> +	struct mm_struct *mm = vma->vm_mm;
> +	pte_t pte;
> +
> +	pte = ptep_get_and_clear(mm, address, ptep);
> +	if (pte_accessible(mm, pte)) {
> +		flush_tlb_page(vma, address);
> +		/*
> +		 * Ensure that the compiler orders our set_pte()
> +		 * after the flush_tlb_page() no matter what.
> +		 */
> +		barrier();

I donât think such a barrier (after remote TLB flush) is needed.
Eventually, if a remote flush takes place, you get csd_lock_wait() to be
called, and then smp_rmb() is called (which is essentially a barrier()
call on x86).

Regards,
Nadav