linux-kernel - Re: [PATCH 7/8] KVM: x86: Trace re-injected exceptions

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Date:   Mon, 04 Apr 2022 15:14:01 +0300
From:   Maxim Levitsky <mlevitsk@...hat.com>
To:     Sean Christopherson <seanjc@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>
Cc:     Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        "Maciej S . Szmigiero" <maciej.szmigiero@...cle.com>
Subject: Re: [PATCH 7/8] KVM: x86: Trace re-injected exceptions

On Sat, 2022-04-02 at 01:09 +0000, Sean Christopherson wrote:
> Trace exceptions that are re-injected, not just those that KVM is
> injecting for the first time.  Debugging re-injection bugs is painful
> enough as is, not having visibility into what KVM is doing only makes
> things worse.
> 
> Signed-off-by: Sean Christopherson <seanjc@...gle.com>
> ---
>  arch/x86/kvm/x86.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 7a066cf92692..384091600bc2 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -9382,6 +9382,10 @@ int kvm_check_nested_events(struct kvm_vcpu *vcpu)
>  
>  static void kvm_inject_exception(struct kvm_vcpu *vcpu)
>  {
> +	trace_kvm_inj_exception(vcpu->arch.exception.nr,
> +				vcpu->arch.exception.has_error_code,
> +				vcpu->arch.exception.error_code);
> +

Can we use a {new tracepoint / new parameter for this tracepoint} for this to avoid confusion?

Best regards,
	Maxim Levitsky



>  	if (vcpu->arch.exception.error_code && !is_protmode(vcpu))
>  		vcpu->arch.exception.error_code = false;
>  	static_call(kvm_x86_queue_exception)(vcpu);
> @@ -9439,10 +9443,6 @@ static int inject_pending_event(struct kvm_vcpu *vcpu, bool *req_immediate_exit)
>  
>  	/* try to inject new event if pending */
>  	if (vcpu->arch.exception.pending) {
> -		trace_kvm_inj_exception(vcpu->arch.exception.nr,
> -					vcpu->arch.exception.has_error_code,
> -					vcpu->arch.exception.error_code);
> -
>  		vcpu->arch.exception.pending = false;
>  		vcpu->arch.exception.injected = true;
>