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Subject: Re: [PATCH] KVM: SVM: Add tracepoint for cr_interception
To:     Vitaly Kuznetsov <vkuznets@redhat.com>
Cc:     "hpa@zytor.com" <hpa@zytor.com>, "bp@alien8.de" <bp@alien8.de>,
        "mingo@redhat.com" <mingo@redhat.com>,
        "tglx@linutronix.de" <tglx@linutronix.de>, joro@8bytes.org,
        "jmattson@google.com" <jmattson@google.com>,
        "wanpengli@tencent.com" <wanpengli@tencent.com>,
        sean.j.christopherson@intel.com,
        "pbonzini@redhat.com" <pbonzini@redhat.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "kvm@vger.kernel.org" <kvm@vger.kernel.org>,
        "x86@kernel.org" <x86@kernel.org>
References: <f3031602-db3b-c4fe-b719-d402663b0a2b@gmail.com>
 <87imctoinr.fsf@vitty.brq.redhat.com>
From:   Haiwei Li <lihaiwei.kernel@gmail.com>
Message-ID: <5b8d366f-db2d-489d-bb48-5c0287323ec6@gmail.com>
Date:   Fri, 4 Sep 2020 20:44:04 +0800
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On 20/9/4 20:01, Vitaly Kuznetsov wrote:
> Haiwei Li <lihaiwei.kernel@gmail.com> writes:
> 
>> From: Haiwei Li <lihaiwei@tencent.com>
>>
>> Add trace_kvm_cr_write and trace_kvm_cr_read for svm.
>>
>> Signed-off-by: Haiwei Li <lihaiwei@tencent.com>
>> ---
>>    arch/x86/kvm/svm/svm.c | 2 ++
>>    1 file changed, 2 insertions(+)
>>
>> diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
>> index 03dd7bac8034..2c6dea48ba62 100644
>> --- a/arch/x86/kvm/svm/svm.c
>> +++ b/arch/x86/kvm/svm/svm.c
>> @@ -2261,6 +2261,7 @@ static int cr_interception(struct vcpu_svm *svm)
> 
> There are two special cases when we go to emulate_on_interception() and
> these won't be logged but I don't think this is a must.
> 
>>    	if (cr >= 16) { /* mov to cr */
>>    		cr -= 16;
>>    		val = kvm_register_read(&svm->vcpu, reg);
>> +		trace_kvm_cr_write(cr, val);
>>    		switch (cr) {
>>    		case 0:
>>    			if (!check_selective_cr0_intercepted(svm, val))
>> @@ -2306,6 +2307,7 @@ static int cr_interception(struct vcpu_svm *svm)
>>    			return 1;
>>    		}
>>    		kvm_register_write(&svm->vcpu, reg, val);
>> +		trace_kvm_cr_read(cr, val);
> 
> The 'default:' case above does 'return 1;' so we won't get the trace but
> I understand you put trace_kvm_cr_read() here so you can log the
> returned 'val', #UD should be clearly visible.
> 
>>    	}
>>    	return kvm_complete_insn_gp(&svm->vcpu, err);
>>    }
>> --
>> 2.18.4
>>
> 
> Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>

Thanks a lot.

>