On Thu, 4 Mar 2021 10:16:53 +0800
Aili Yao <yaoa...@kingsoft.com> wrote:
> On Wed, 3 Mar 2021 15:41:35 +0000
> "Luck, Tony" <tony.l...@intel.com> wrote:
>
> > > For error address with sigbus, i think this is not an issue resulted by
> > > the patch i post, before my patch, the issue is already there.
> > > I don't find a realizable way to get the correct address for same reason
> > > --- we don't know whether the page mapping is there or not when
> > > we got to kill_me_maybe(), in some case, we may get it, but there are a
> > > lot of parallel issue need to consider, and if failed we have to fallback
> > > to the error brach again, remaining current code may be an easy option;
> > >
> >
> > My RFC patch from yesterday removes the uncertainty about whether the page
> > is there or not. After it walks the page
> > tables we know that the poison page isn't mapped (note that patch is RFC
> > for a reason ... I'm 90% sure that it should
> > do a bit more that just clear the PRESENT bit).
> >
> > So perhaps memory_failure() has queued a SIGBUS for this task, if so, we
> > take it when we return from kill_me_maybe()
And when this happen, the process will receive an SIGBUS with AO level, is it
proper as not an AR?
> > If not, we will return to user mode and re-execute the failing instruction
> > ... but because the page is unmapped we will take a #PF
>
> Got this, I have some error thoughts here.
>
>
> > The x86 page fault handler will see that the page for this physical address
> > is marked HWPOISON, and it will send the SIGBUS
> > (just like it does if the page had been removed by an earlier UCNA/SRAO
> > error).
>
> if your methods works, should it be like this?
>
> 1582 pteval =
> swp_entry_to_pte(make_hwpoison_entry(subpage));
> 1583 if (PageHuge(page)) {
> 1584 hugetlb_count_sub(compound_nr(page), mm);
> 1585 set_huge_swap_pte_at(mm, address,
> 1586 pvmw.pte, pteval,
> 1587
> vma_mmu_pagesize(vma));
> 1588 } else {
> 1589 dec_mm_counter(mm, mm_counter(page));
> 1590 set_pte_at(mm, address, pvmw.pte,
> pteval);
> 1591 }
>
> the page fault check if it's a poison page using is_hwpoison_entry(),
>
And if it works, does we need some locking mechanism before we call
walk_page_range();
if we lock, does we need to process the blocking interrupted error as other
places will do?
--
Thanks!
Aili Yao
