Re: [PATCH v11 08/11] KVM: x86/pmu: Emulate LBR feature via guest LBR event

[Xu, Like]

On 2020/5/19 19:03, Peter Zijlstra wrote:
> On Thu, May 14, 2020 at 04:30:51PM +0800, Like Xu wrote:
> > @@ -6698,6 +6698,7 @@ static fastpath_t vmx_vcpu_run(struct kvm_vcpu *vcpu)
> >   
> >   	if (vcpu_to_pmu(vcpu)->version)
> >   		atomic_switch_perf_msrs(vmx);
> > +
> >   	atomic_switch_umwait_control_msr(vmx);
> >   
> >   	if (enable_preemption_timer)
> Is this where the test to see if any of the KVM events went into ERROR
> state should go?
Yes, I chose the same location to do LBR availability check in the next 
patch 0010.

Actually for normal vPMU counters and their events,
I'm not sure whether pr_warn() should also be used widely.

The current approach is to keep vPMC silent when it may be inaccurate.

I may need @Paolo's attitude on this issue.

Thanks,
Like Xu
> 	if (event->state == PERF_EVENT_STATE_ERROR) {
> 		pr_warn("unhappy, someone stole our counter\n");
> 	}
>
> like..