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From:   Suren Baghdasaryan <surenb@google.com>
Date:   Wed, 5 Jul 2023 10:22:27 -0700
Message-ID: <CAJuCfpGTNF9BWBxZoqYKSDrtq=iJoN1n8oTc=Yu0pPzW8cs8rQ@mail.gmail.com>
Subject: Re: [PATCH v3 2/2] mm: disable CONFIG_PER_VMA_LOCK until its fixed
To:     David Hildenbrand <david@redhat.com>
Cc:     akpm@linux-foundation.org, jirislaby@kernel.org,
        jacobly.alt@gmail.com, holger@applied-asynchrony.com,
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On Wed, Jul 5, 2023 at 10:16=E2=80=AFAM David Hildenbrand <david@redhat.com=
> wrote:
>
> On 05.07.23 19:12, Suren Baghdasaryan wrote:
> > A memory corruption was reported in [1] with bisection pointing to the
> > patch [2] enabling per-VMA locks for x86.
> > Disable per-VMA locks config to prevent this issue while the problem is
> > being investigated. This is expected to be a temporary measure.
> >
> > [1] https://bugzilla.kernel.org/show_bug.cgi?id=3D217624
> > [2] https://lore.kernel.org/all/20230227173632.3292573-30-surenb@google=
.com
> >
> > Reported-by: Jiri Slaby <jirislaby@kernel.org>
> > Closes: https://lore.kernel.org/all/dbdef34c-3a07-5951-e1ae-e9c6e3cdf51=
b@kernel.org/
> > Reported-by: Jacob Young <jacobly.alt@gmail.com>
> > Closes: https://bugzilla.kernel.org/show_bug.cgi?id=3D217624
> > Fixes: 0bff0aaea03e ("x86/mm: try VMA lock-based page fault handling fi=
rst")
> > Cc: stable@vger.kernel.org
> > Signed-off-by: Suren Baghdasaryan <surenb@google.com>
> > ---
> >   mm/Kconfig | 3 ++-
> >   1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/mm/Kconfig b/mm/Kconfig
> > index 09130434e30d..0abc6c71dd89 100644
> > --- a/mm/Kconfig
> > +++ b/mm/Kconfig
> > @@ -1224,8 +1224,9 @@ config ARCH_SUPPORTS_PER_VMA_LOCK
> >          def_bool n
> >
> >   config PER_VMA_LOCK
> > -     def_bool y
> > +     bool "Enable per-vma locking during page fault handling."
> >       depends on ARCH_SUPPORTS_PER_VMA_LOCK && MMU && SMP
> > +     depends on BROKEN
> >       help
> >         Allow per-vma locking during page fault handling.
> >
> Do we have any testing results (that don't reveal other issues :) ) for
> patch #1? Not sure if we really want to mark it broken if patch #1 fixes
> the issue.

I tested the fix using the only reproducer provided in the reports
plus kernel compilation and my fork stress test. All looked good and
stable but I don't know if other reports had the same issue or
something different.
I think the urgency to disable the feature stems from the timeline
being very close to when distributions will start using the 6.4 stable
kernel version.

>
> --
> Cheers,
>
> David / dhildenb
>