linux-kernel - Re: [PATCH v2 2/9] mm/hugetlb: separate path for hwpoison entry in copy_hugetlb_page

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Message-ID: <20220627064830.GC2159330@hori.linux.bs1.fc.nec.co.jp>
Date:   Mon, 27 Jun 2022 06:48:31 +0000
From:   HORIGUCHI NAOYA(堀口　直也) 
        <naoya.horiguchi@....com>
To:     Mike Kravetz <mike.kravetz@...cle.com>
CC:     Naoya Horiguchi <nao.horiguchi@...il.com>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        David Hildenbrand <david@...hat.com>,
        Miaohe Lin <linmiaohe@...wei.com>,
        Liu Shixin <liushixin2@...wei.com>,
        Yang Shi <shy828301@...il.com>,
        Oscar Salvador <osalvador@...e.de>,
        Muchun Song <songmuchun@...edance.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 2/9] mm/hugetlb: separate path for hwpoison entry in
 copy_hugetlb_page_range()

On Fri, Jun 24, 2022 at 01:57:57PM -0700, Mike Kravetz wrote:
> On 06/24/22 08:51, Naoya Horiguchi wrote:
> > From: Naoya Horiguchi <naoya.horiguchi@....com>
> > 
> > Originally copy_hugetlb_page_range() handles migration entries and hwpoisone
> > entries in similar manner.  But recently the related code path has more code
> > for migration entries, and when is_writable_migration_entry() was converted
> > to !is_readable_migration_entry(), hwpoison entries on source processes got
> > to be unexpectedly updated (which is legitimate for migration entries, but
> > not for hwpoison entries).  This results in unexpected serious issues like
> > kernel panic when foking processes with hwpoison entries in pmd.
> > 
> > Separate the if branch into one for hwpoison entries and one for migration
> > entries.
> > 
> > Fixes: 6c287605fd56 ("mm: remember exclusively mapped anonymous pages with PG_anon_exclusive")
> > Signed-off-by: Naoya Horiguchi <naoya.horiguchi@....com>
> > Cc: <stable@...r.kernel.org> # 5.18
> > ---
> >  mm/hugetlb.c | 9 +++++++--
> >  1 file changed, 7 insertions(+), 2 deletions(-)
> 
> Thank you!
> 
> Reviewed-by: Mike Kravetz <mike.kravetz@...cle.com>
> (with typos pointed out by Miaohe Lin)
> 
> Just curious, are there any hwpoisoned tests in any test suite?  I run
> libhugetlbfs tests and ltp on a regular basis which sometimes catch
> regressions.  If there are no tests in any suite today, this might be
> something we want to consider for future work.

mce-tests (https://git.kernel.org/pub/scm/utils/cpu/mce/mce-test.git) has
some test cases about hwpoison (under cases/function/hwpoison/), but this
tool mostly focuses on MCE and does not have enough hwpoison testcases.
So I'm maintaining my own test suite
(https://github.com/nhoriguchi/mm_regression) for long to help my own
hwpoison development/maintenance.  I'd like to make this tool more handy
so that other developers or testsuites can easily run the hwpoison testing,
although I need more work for it.

Thanks,
Naoya Horiguchi