linux-kernel - Re: [PATCH] kvm: tracing: Fix unmatched kvm_entry and kvm

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Date:   Sat, 16 Jan 2021 02:25:57 +0100
From:   Dario Faggioli <dfaggioli@...e.com>
To:     linux-kernel@...r.kernel.org
Cc:     Lorenzo Brescia <lorenzo.brescia@....unito.it>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org
Subject: Re: [PATCH] kvm: tracing: Fix unmatched kvm_entry and kvm_exit
 events

On Wed, 2020-12-23 at 14:45 +0000, Dario Faggioli wrote:
> From: Lorenzo Brescia <lorenzo.brescia@....unito.it>
> 
> On VMX, if we exit and then re-enter immediately without leaving
> the vmx_vcpu_run() function, the kvm_entry event is not logged.
> That means we will see one (or more) kvm_exit, without its (their)
> corresponding kvm_entry, as shown here:
> 
>  CPU-1979 [002] 89.871187: kvm_entry: vcpu 1
>  CPU-1979 [002] 89.871218: kvm_exit:  reason MSR_WRITE
>  CPU-1979 [002] 89.871259: kvm_exit:  reason MSR_WRITE
> 
> It also seems possible for a kvm_entry event to be logged, but then
> we leave vmx_vcpu_run() right away (if vmx->emulation_required is
> true). In this case, we will have a spurious kvm_entry event in the
> trace.
> 
Gentle ping... :-)

Thanks and Regards

-- 
Dario Faggioli, Ph.D
http://about.me/dario.faggioli
Virtualization Software Engineer
SUSE Labs, SUSE https://www.suse.com/
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