linux-kernel - Re: [PATCH] KVM: LAPIC: Also cancel preemption timer when disarm LAPIC timer

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Message-ID: <CANRm+Cx8sNJmwB3kYWxfcWJNi9A3AdAtLdpwMduiRTfkz2PJVw@mail.gmail.com>
Date:   Wed, 25 Mar 2020 08:16:13 +0800
From:   Wanpeng Li <kernellwp@...il.com>
To:     Vitaly Kuznetsov <vkuznets@...hat.com>
Cc:     LKML <linux-kernel@...r.kernel.org>, kvm <kvm@...r.kernel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>
Subject: Re: [PATCH] KVM: LAPIC: Also cancel preemption timer when disarm
 LAPIC timer

On Tue, 24 Mar 2020 at 23:24, Vitaly Kuznetsov <vkuznets@...hat.com> wrote:
>
> Wanpeng Li <kernellwp@...il.com> writes:
>
> > From: Wanpeng Li <wanpengli@...cent.com>
> >
> > The timer is disarmed when switching between TSC deadline and other modes,
> > we should set everything to disarmed state, however, LAPIC timer can be
> > emulated by preemption timer, it still works if vmx->hv_deadline_timer is
> > not -1. This patch also cancels preemption timer when disarm LAPIC timer.
> >
> > Signed-off-by: Wanpeng Li <wanpengli@...cent.com>
> > ---
> >  arch/x86/kvm/lapic.c | 6 ++++++
> >  1 file changed, 6 insertions(+)
> >
> > diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
> > index 338de38..a38f1a8 100644
> > --- a/arch/x86/kvm/lapic.c
> > +++ b/arch/x86/kvm/lapic.c
> > @@ -1445,6 +1445,8 @@ static void limit_periodic_timer_frequency(struct kvm_lapic *apic)
> >       }
> >  }
> >
> > +static void cancel_hv_timer(struct kvm_lapic *apic);
> > +
>
> Nitpick: cancel_hv_timer() is only 4 lines long so I'd suggest we move
> it instead of adding a forward declaration.

There are other preemption timer operations like start_hv_timer etc
around cancel_hv_timer, so it is not that suitable to move directly.

    Wanpeng