linux-kernel - Re: [PATCH 2/2] KVM: SVM: Introduce trace point for the slow-path of avic_kic_target

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Date:   Mon, 18 Apr 2022 14:03:21 +0300
From:   Maxim Levitsky <mlevitsk@...hat.com>
To:     Suravee Suthikulpanit <suravee.suthikulpanit@....com>,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc:     pbonzini@...hat.com, seanjc@...gle.com, joro@...tes.org,
        jon.grimm@....com, wei.huang2@....com, terry.bowman@....com
Subject: Re: [PATCH 2/2] KVM: SVM: Introduce trace point for the slow-path
 of avic_kic_target_vcpus

On Thu, 2022-04-14 at 00:11 -0500, Suravee Suthikulpanit wrote:
> This can help identify potential performance issues when handles
> AVIC incomplete IPI due vCPU not running.
> 
> Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@....com>
> ---
>  arch/x86/kvm/svm/avic.c |  2 ++
>  arch/x86/kvm/trace.h    | 20 ++++++++++++++++++++
>  arch/x86/kvm/x86.c      |  1 +
>  3 files changed, 23 insertions(+)
> 
> diff --git a/arch/x86/kvm/svm/avic.c b/arch/x86/kvm/svm/avic.c
> index 92d8e0de1fb4..e5fb4931a2f1 100644
> --- a/arch/x86/kvm/svm/avic.c
> +++ b/arch/x86/kvm/svm/avic.c
> @@ -440,6 +440,8 @@ static void avic_kick_target_vcpus(struct kvm *kvm, struct kvm_lapic *source,
>  	if (!avic_kick_target_vcpus_fast(kvm, source, icrl, icrh, index))
>  		return;
>  
> +	trace_kvm_avic_kick_vcpu_slowpath(icrh, icrl, index);
> +
>  	/*
>  	 * Wake any target vCPUs that are blocking, i.e. waiting for a wake
>  	 * event.  There's no need to signal doorbells, as hardware has handled
> diff --git a/arch/x86/kvm/trace.h b/arch/x86/kvm/trace.h
> index e3a24b8f04be..de4762517569 100644
> --- a/arch/x86/kvm/trace.h
> +++ b/arch/x86/kvm/trace.h
> @@ -1459,6 +1459,26 @@ TRACE_EVENT(kvm_avic_ga_log,
>  		  __entry->vmid, __entry->vcpuid)
>  );
>  
> +TRACE_EVENT(kvm_avic_kick_vcpu_slowpath,
> +	    TP_PROTO(u32 icrh, u32 icrl, u32 index),
> +	    TP_ARGS(icrh, icrl, index),
> +
> +	TP_STRUCT__entry(
> +		__field(u32, icrh)
> +		__field(u32, icrl)
> +		__field(u32, index)
> +	),
> +
> +	TP_fast_assign(
> +		__entry->icrh = icrh;
> +		__entry->icrl = icrl;
> +		__entry->index = index;
> +	),
> +
> +	TP_printk("icrh:icrl=%#08x:%08x, index=%u",
> +		  __entry->icrh, __entry->icrl, __entry->index)
> +);
> +
>  TRACE_EVENT(kvm_hv_timer_state,
>  		TP_PROTO(unsigned int vcpu_id, unsigned int hv_timer_in_use),
>  		TP_ARGS(vcpu_id, hv_timer_in_use),
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index d0fac57e9996..c2da6c7516b0 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -12978,6 +12978,7 @@ EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_pi_irte_update);
>  EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_avic_unaccelerated_access);
>  EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_avic_incomplete_ipi);
>  EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_avic_ga_log);
> +EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_avic_kick_vcpu_slowpath);
>  EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_apicv_accept_irq);
>  EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_vmgexit_enter);
>  EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_vmgexit_exit);

Reviewed-by: Maxim Levitsky <mlevitsk@...hat.com>

Best regards,
        Maxim Levitsky