> -----Original Message-----
> From: Sean Christopherson <seanjc@xxxxxxxxxx>
> Sent: Thursday, October 13, 2022 12:06 AM
> To: Li,Rongqing <lirongqing@xxxxxxxxx>
> Cc: kvm@xxxxxxxxxxxxxxx; Peter Shier <pshier@xxxxxxxxxx>; Jim Mattson
> <jmattson@xxxxxxxxxx>; Wanpeng Li <wanpengli@xxxxxxxxxxx>
> Subject: Re: [PATCH][RFC] KVM: x86: Don't reset deadline to period when timer
> is in one shot mode
>
> +Jim, Peter, and Wanpeng
>
> On Wed, Oct 12, 2022, Li RongQing wrote:
> > In one-shot mode, the APIC timer stops counting when the timer reaches
> > zero, so don't reset deadline to period for one shot mode
> >
> > Signed-off-by: Li RongQing <lirongqing@xxxxxxxxx>
> > ---
> > arch/x86/kvm/lapic.c | 8 ++++++--
> > 1 file changed, 6 insertions(+), 2 deletions(-)
> >
> > diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c index
> > 9dda989..bf39027 100644
> > --- a/arch/x86/kvm/lapic.c
> > +++ b/arch/x86/kvm/lapic.c
> > @@ -1840,8 +1840,12 @@ static bool set_target_expiration(struct kvm_lapic
> *apic, u32 count_reg)
> > if (unlikely(count_reg != APIC_TMICT)) {
> > deadline = tmict_to_ns(apic,
> > kvm_lapic_get_reg(apic, count_reg));
> > - if (unlikely(deadline <= 0))
> > - deadline = apic->lapic_timer.period;
> > + if (unlikely(deadline <= 0)) {
> > + if (apic_lvtt_period(apic))
> > + deadline = apic->lapic_timer.period;
> > + else
> > + deadline = 0;
> > + }
>
> This is not the standard "count has reached zero" path, it's the "vCPU is
> migrated and the timer needs to be resumed on the destination" path.
> Zeroing the deadline here will not squash the timer, IIUC it will cause the timer
> to immediately fire.
>
> That said, I think the patch is actually correct
Should we set deadline to 0 when it is expired whether the timer is one shot mode or period mode ?
>even though the shortlog+changelog are wrong.
I will rewrite it
Thanks
-Li
