linux-kernel - Re: WARNING: suspicious RCU usage - while installing a VM on a CPU listed under nohz

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Date:   Wed, 29 Jul 2020 10:38:18 +0800
From:   Wanpeng Li <kernellwp@...il.com>
To:     Nitesh Narayan Lal <nitesh@...hat.com>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        KVM list <kvm@...r.kernel.org>,
        Wanpeng Li <wanpengli@...cent.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Liran Alon <liran.alon@...cle.com>,
        "frederic@...nel.org" <frederic@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Juri Lelli <juri.lelli@...hat.com>
Subject: Re: WARNING: suspicious RCU usage - while installing a VM on a CPU
 listed under nohz_full

Hi Nitesh，
On Wed, 29 Jul 2020 at 09:00, Wanpeng Li <kernellwp@...il.com> wrote:
>
> On Tue, 28 Jul 2020 at 22:40, Nitesh Narayan Lal <nitesh@...hat.com> wrote:
> >
> > Hi,
> >
> > I have recently come across an RCU trace with the 5.8-rc7 kernel that has the
> > debug configs enabled while installing a VM on a CPU that is listed under
> > nohz_full.
> >
> > Based on some of the initial debugging, my impression is that the issue is
> > triggered because of the fastpath that is meant to optimize the writes to x2APIC
> > ICR that eventually leads to a virtual IPI in fixed delivery mode, is getting
> > invoked from the quiescent state.

Could you try latest linux-next tree? I guess maybe some patches are
pending in linux-next tree, I can't reproduce against linux-next tree.