Re: [PATCH v3 1/2] KVM: X86: Less kvmclock sync induced vmexits after VM boots

[Wanpeng Li <kernellwp@xxxxxxxxx>]

On Mon, 17 Feb 2020 at 19:23, Paolo Bonzini <pbonzini@xxxxxxxxxx> wrote:
>
> On 17/02/20 11:36, Wanpeng Li wrote:
> >
> > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> > index fb5d64e..d0ba2d4 100644
> > --- a/arch/x86/kvm/x86.c
> > +++ b/arch/x86/kvm/x86.c
> > @@ -9390,8 +9390,9 @@ void kvm_arch_vcpu_postcreate(struct kvm_vcpu *vcpu)
> >      if (!kvmclock_periodic_sync)
> >          return;
> >
> > -    schedule_delayed_work(&kvm->arch.kvmclock_sync_work,
> > -                    KVMCLOCK_SYNC_PERIOD);
> > +    if (kvm->created_vcpus == 1)
> > +        schedule_delayed_work(&kvm->arch.kvmclock_sync_work,
> > +                        KVMCLOCK_SYNC_PERIOD);
>
> This is called with kvm->lock not held, so you can have
> kvm->created_vcpus == 2 by the time you get here.  You can test instead
> "if (vcpu->vcpu_idx == 0)".

Agreed.

    Wanpeng