linux-kernel - Re: [PATCH 5/7] KVM: SVM: Add VNMI support in inject

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Date:   Fri, 17 Jun 2022 20:35:21 +0530
From:   "Shukla, Santosh" <santosh.shukla@....com>
To:     Maxim Levitsky <mlevitsk@...hat.com>,
        Paolo Bonzini <pbonzini@...hat.com>
Cc:     Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        Tom Lendacky <thomas.lendacky@....com>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 5/7] KVM: SVM: Add VNMI support in inject_nmi



On 6/7/2022 6:44 PM, Maxim Levitsky wrote:
> On Thu, 2022-06-02 at 19:56 +0530, Santosh Shukla wrote:
>> Inject the NMI by setting V_NMI in the VMCB interrupt control. processor
>> will clear V_NMI to acknowledge processing has started and will keep the
>> V_NMI_MASK set until the processor is done with processing the NMI event.
>>
>> Signed-off-by: Santosh Shukla <santosh.shukla@....com>
>> ---
>>  arch/x86/kvm/svm/svm.c | 7 ++++++-
>>  1 file changed, 6 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
>> index a405e414cae4..200f979169e0 100644
>> --- a/arch/x86/kvm/svm/svm.c
>> +++ b/arch/x86/kvm/svm/svm.c
>> @@ -3385,11 +3385,16 @@ static void svm_inject_nmi(struct kvm_vcpu *vcpu)
>>  {
>>         struct vcpu_svm *svm = to_svm(vcpu);
>>  
>> +       ++vcpu->stat.nmi_injections;
>> +       if (is_vnmi_enabled(svm->vmcb)) {
>> +               svm->vmcb->control.int_ctl |= V_NMI_PENDING;
>> +               return;
>> +       }
> Here I would advice to have a warning to check if vNMI is already pending.
> 
Yes, in v2.

> Also we need to check what happens if we make vNMI pending and get #SMI,
> while in #NMI handler, or if #NMI is blocked due to interrupt window.
>

V_NMI_MASK should be saved as 1 in the save area and
hypervisor will resume the NMI handler after handling the SMI.

Thanks,
Santosh
 
> Best regards,
> 	Maxim Levitsky
> 
> 
>> +
>>         svm->vmcb->control.event_inj = SVM_EVTINJ_VALID | SVM_EVTINJ_TYPE_NMI;
>>         vcpu->arch.hflags |= HF_NMI_MASK;
>>         if (!sev_es_guest(vcpu->kvm))
>>                 svm_set_intercept(svm, INTERCEPT_IRET);
>> -       ++vcpu->stat.nmi_injections;
>>  }
>>  
>>  static void svm_inject_irq(struct kvm_vcpu *vcpu)
> 
>