On Thu, 4 Mar 2021 12:19:41 +0800
Aili Yao <yaoa...@kingsoft.com> wrote:
> 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?
>
And another thing:
Do we need a call to flush_tlb_page(vma, address) to make the pte changes into
effect?
--
Thanks!
Aili Yao
