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From:   Marco Elver <elver@google.com>
Date:   Thu, 9 Apr 2020 09:03:12 +0200
Message-ID: <CANpmjNMiHNVh3BVxZUqNo4jW3DPjoQPrn-KEmAJRtSYORuryEA@mail.gmail.com>
Subject: Re: KCSAN + KVM = host reset
To:     Qian Cai <cai@lca.pw>
Cc:     Paolo Bonzini <pbonzini@redhat.com>,
        "paul E. McKenney" <paulmck@kernel.org>,
        kasan-dev <kasan-dev@googlegroups.com>,
        LKML <linux-kernel@vger.kernel.org>, kvm@vger.kernel.org
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On Wed, 8 Apr 2020 at 23:29, Qian Cai <cai@lca.pw> wrote:
>
>
>
> > On Apr 8, 2020, at 5:25 PM, Paolo Bonzini <pbonzini@redhat.com> wrote:
> >
> > On 08/04/20 22:59, Qian Cai wrote:
> >> Running a simple thing on this AMD host would trigger a reset right aw=
ay.
> >> Unselect KCSAN kconfig makes everything work fine (the host would also
> >> reset If only "echo off > /sys/kernel/debug/kcsan=E2=80=9D before runn=
ing qemu-kvm).
> >
> > Is this a regression or something you've just started to play with?  (I=
f
> > anything, the assembly language conversion of the AMD world switch that
> > is in linux-next could have reduced the likelihood of such a failure,
> > not increased it).
>
> I don=E2=80=99t remember I had tried this combination before, so don=E2=
=80=99t know if it is a
> regression or not.

What happens with KASAN? My guess is that, since it also happens with
"off", something that should not be instrumented is being
instrumented.

What happens if you put a 'KCSAN_SANITIZE :=3D n' into
arch/x86/kvm/Makefile? Since it's hard for me to reproduce on this
exact system, I'd ask you to narrow it down by placing 'KCSAN_SANITIZE
:=3D n' into suspect subsystems' Makefiles. Once you get it to work with
that, we can refine the solution.

Thanks,
-- Marco