On 6/7/2022 6:42 PM, Maxim Levitsky wrote:
> On Tue, 2022-06-07 at 16:10 +0300, Maxim Levitsky wrote:
>> On Thu, 2022-06-02 at 19:56 +0530, Santosh Shukla wrote:
>>> In the VNMI case, Report NMI is not allowed when the processor set the
>>> V_NMI_MASK to 1 which means the Guest is busy handling VNMI.
>>>
>>> Signed-off-by: Santosh Shukla <santosh.shukla@xxxxxxx>
>>> ---
>>> arch/x86/kvm/svm/svm.c | 6 ++++++
>>> 1 file changed, 6 insertions(+)
>>>
>>> diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
>>> index d67a54517d95..a405e414cae4 100644
>>> --- a/arch/x86/kvm/svm/svm.c
>>> +++ b/arch/x86/kvm/svm/svm.c
>>> @@ -3483,6 +3483,9 @@ bool svm_nmi_blocked(struct kvm_vcpu *vcpu)
>>> struct vmcb *vmcb = svm->vmcb;
>>> bool ret;
>>>
>>> + if (is_vnmi_enabled(vmcb) && is_vnmi_mask_set(vmcb))
>>> + return true;
>>
>> How does this interact with GIF? if the guest does clgi, will the
>> CPU update the V_NMI_MASK on its own If vGIF is enabled?
>>
Yes.
>> What happens if vGIF is disabled and vNMI is enabled? KVM then intercepts
>> the stgi/clgi, and it should then update the V_NMI_MASK?
>>
No.
For both case - HW takes the V_NMI event at the boundary of VMRUN instruction.
>>
>>
>>
>>> +
>>> if (!gif_set(svm))
>>> return true;
>>>
>>> @@ -3618,6 +3621,9 @@ static void svm_enable_nmi_window(struct kvm_vcpu *vcpu)
>>> {
>>> struct vcpu_svm *svm = to_svm(vcpu);
>>>
>>> + if (is_vnmi_enabled(svm->vmcb) && is_vnmi_mask_set(svm->vmcb))
>>> + return;
>>
>> This might have hidden assumption that we will only enable NMI window when vNMI is masked.
>
> Also what if vNMI is already pending?
>
If V_NMI_MASK set, that means V_NMI is pending, if so then inject another V_NMI in next VMRUN.
Thanks,
Santosh
> Best regards,
> Maxim Levitsky
>>
>>
>>
>>> +
>>> if ((vcpu->arch.hflags & (HF_NMI_MASK | HF_IRET_MASK)) == HF_NMI_MASK)
>>> return; /* IRET will cause a vm exit */
>>>
>>
>>
>> Best regards,
>> Maxim Levitsky
>
>
