Re: [PATCH v11 05/11] perf/x86: Keep LBR stack unchanged in host context for guest LBR event

[Peter Zijlstra]

On Thu, May 14, 2020 at 04:30:48PM +0800, Like Xu wrote:
> @@ -544,7 +562,12 @@ void intel_pmu_lbr_enable_all(bool pmi)
>  {
>  	struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
>  
> -	if (cpuc->lbr_users)
> +	/*
> +	 * When the LBR hardware is scheduled for a guest LBR event,
> +	 * the guest will dis/enables LBR itself at the appropriate time,
> +	 * including configuring MSR_LBR_SELECT.
> +	 */
> +	if (cpuc->lbr_users && !cpuc->guest_lbr_enabled)
>  		__intel_pmu_lbr_enable(pmi);
>  }

No!, that should be done through perf_event_attr::exclude_host, as I
believe all the other KVM event do it.