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Subject: Re: [PATCH] KVM: nVMX: Fix the NMI IDT-vectoring info handling
To: Wanpeng Li <kernellwp@gmail.com>, Paolo Bonzini <pbonzini@redhat.com>
References: <1474515259-3197-1-git-send-email-wanpeng.li@hotmail.com>
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Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        kvm <kvm@vger.kernel.org>, Wanpeng Li <wanpeng.li@hotmail.com>,
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        Bandan Das <bsd@redhat.com>
From: Jan Kiszka <jan.kiszka@siemens.com>
Message-ID: <c2367d8a-96a1-ee49-27c4-d9a98489ae5d@siemens.com>
Date: Thu, 22 Sep 2016 12:04:30 +0200
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On 2016-09-22 11:45, Wanpeng Li wrote:
> 2016-09-22 17:37 GMT+08:00 Paolo Bonzini <pbonzini@redhat.com>:
>>
>>
>> On 22/09/2016 05:34, Wanpeng Li wrote:
>>> -     if (vmx->rmode.vm86_active) {
>>> -             if (kvm_inject_realmode_interrupt(vcpu, NMI_VECTOR, 0) != EMULATE_DONE)
>>> -                     kvm_make_request(KVM_REQ_TRIPLE_FAULT, vcpu);
>>> -             return;
>>> +             ++vcpu->stat.nmi_injections;
>>> +             vmx->nmi_known_unmasked = false;
>>> +             if (vmx->rmode.vm86_active) {
>>> +                     if (kvm_inject_realmode_interrupt(vcpu, NMI_VECTOR, 0) != EMULATE_DONE)
>>> +                             kvm_make_request(KVM_REQ_TRIPLE_FAULT, vcpu);
>>> +                     return;
>>> +             }
>>>       }
>>>       vmcs_write32(VM_ENTRY_INTR_INFO_FIELD,
>>>                       INTR_TYPE_NMI_INTR | INTR_INFO_VALID_MASK | NMI_VECTOR);
>>
>> Hi,
>>
>> the patch is mostly okay but the "if (vmx->rmode.vm86_active)" part
>> should be done also if the VCPU is in guest mode.  See
>> vmx_queue_exception for a similar example.
> 
> Thanks for pointing out. :)
> 
>>
>> I would like to know which processors lack virtual NMI support.  I'd
>> rather rip that code out...
> 
> At least the Sandy Bridge server on my hand supports Virtual NMIs, I
> don't have machine older than this.

IIRC, my last-but-one notebook was lacking vNMI, and that was a Core 2
Duo. Maybe there are embedded product out there relying on this
emulation, but I don't have any evidence.

Jan

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