linux-kernel - Re: [RFC 2/3] x86: KVM: stats: Add stat counter for IRQs injected via APICv

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Message-ID: <56130d48-706f-d1d0-bd23-69544298f353@oracle.com>
Date: Thu, 15 Feb 2024 08:16:55 -0800
From: Dongli Zhang <dongli.zhang@...cle.com>
To: Alejandro Jimenez <alejandro.j.jimenez@...cle.com>, kvm@...r.kernel.org
Cc: seanjc@...gle.com, pbonzini@...hat.com, linux-kernel@...r.kernel.org,
        joao.m.martins@...cle.com, boris.ostrovsky@...cle.com,
        mark.kanda@...cle.com, suravee.suthikulpanit@....com,
        mlevitsk@...hat.com
Subject: Re: [RFC 2/3] x86: KVM: stats: Add stat counter for IRQs injected via
 APICv

Hi Alejandro,

Is there any use case of this counter in the bug?

E.g., there are already trace_kvm_apicv_accept_irq() there. The ftrace or ebpf
would be able to tell if the hardware accelerated interrupt delivery is active?.

Any extra benefits? E.g., if this counter may need to match with any other
counter in the KVM/guest so that a bug can be detected? That will be very helpful.

Thank you very much!

Dongli Zhang

On 2/15/24 08:01, Alejandro Jimenez wrote:
> Export binary stat counting how many interrupts have been delivered via
> APICv/AVIC acceleration from the host. This is one of the most reliable
> methods to detect when hardware accelerated interrupt delivery is active,
> since APIC timer interrupts are regularly injected and exercise these
> code paths.
> 
> Signed-off-by: Alejandro Jimenez <alejandro.j.jimenez@...cle.com>
> ---
>  arch/x86/include/asm/kvm_host.h | 1 +
>  arch/x86/kvm/svm/svm.c          | 3 +++
>  arch/x86/kvm/vmx/vmx.c          | 2 ++
>  arch/x86/kvm/x86.c              | 1 +
>  4 files changed, 7 insertions(+)
> 
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index 9b960a523715..b6f18084d504 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -1564,6 +1564,7 @@ struct kvm_vcpu_stat {
>  	u64 preemption_other;
>  	u64 guest_mode;
>  	u64 notify_window_exits;
> +	u64 apicv_accept_irq;
>  };
>  
>  struct x86_instruction_info;
> diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
> index e90b429c84f1..2243af08ed39 100644
> --- a/arch/x86/kvm/svm/svm.c
> +++ b/arch/x86/kvm/svm/svm.c
> @@ -3648,6 +3648,9 @@ void svm_complete_interrupt_delivery(struct kvm_vcpu *vcpu, int delivery_mode,
>  	}
>  
>  	trace_kvm_apicv_accept_irq(vcpu->vcpu_id, delivery_mode, trig_mode, vector);
> +
> +	++vcpu->stat.apicv_accept_irq;
> +
>  	if (in_guest_mode) {
>  		/*
>  		 * Signal the doorbell to tell hardware to inject the IRQ.  If
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index d4e6625e0a9a..f7db75ae2c55 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -4275,6 +4275,8 @@ static void vmx_deliver_interrupt(struct kvm_lapic *apic, int delivery_mode,
>  	} else {
>  		trace_kvm_apicv_accept_irq(vcpu->vcpu_id, delivery_mode,
>  					   trig_mode, vector);
> +
> +		++vcpu->stat.apicv_accept_irq;
>  	}
>  }
>  
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index f7f598f066e7..2ad70cf6e52c 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -304,6 +304,7 @@ const struct _kvm_stats_desc kvm_vcpu_stats_desc[] = {
>  	STATS_DESC_COUNTER(VCPU, preemption_other),
>  	STATS_DESC_IBOOLEAN(VCPU, guest_mode),
>  	STATS_DESC_COUNTER(VCPU, notify_window_exits),
> +	STATS_DESC_COUNTER(VCPU, apicv_accept_irq),
>  };
>  
>  const struct kvm_stats_header kvm_vcpu_stats_header = {