Gleb Natapov wrote on 2012-12-05:
> On Wed, Dec 05, 2012 at 03:43:41AM +0000, Zhang, Yang Z wrote:
>>>> @@ -5657,12 +5673,20 @@ static int vcpu_enter_guest(struct kvm_vcpu
>>> *vcpu)
>>>> }
>>>>
>>>> if (kvm_check_request(KVM_REQ_EVENT, vcpu) || req_int_win) {
>>>> + /* update archtecture specific hints for APIC
>>>> + * virtual interrupt delivery */
>>>> + if (kvm_x86_ops->update_irq)
>>>> + kvm_x86_ops->update_irq(vcpu);
>>>> +
>>>> inject_pending_event(vcpu);
>>>>
>>>> /* enable NMI/IRQ window open exits if needed */
>>>> if (vcpu->arch.nmi_pending)
>>>> kvm_x86_ops->enable_nmi_window(vcpu);
>>>> - else if (kvm_cpu_has_interrupt(vcpu) || req_int_win)
>>>> + else if (kvm_apic_vid_enabled(vcpu)) {
>>>> + if (kvm_cpu_has_extint(vcpu))
>>>> + kvm_x86_ops->enable_irq_window(vcpu);
>>>
>>> If RVI is non-zero, then interrupt window should not be enabled,
>>> accordingly to 29.2.2:
>>>
>>> "If a virtual interrupt has been recognized (see Section 29.2.1), it will
>>> be delivered at an instruction boundary when the following conditions all
>>> hold: (1) RFLAGS.IF = 1; (2) there is no blocking by STI; (3) there is no
>>> blocking by MOV SS or by POP SS; and (4) the "interrupt-window exiting"
>>> VM-execution control is 0."
>> Right. Must check RVI here.
>>
> Why? We request interrupt window here because there is ExtINT interrupt
> pending. ExtINT interrupt has a precedence over APIC interrupts (our
> current code is incorrect!), so we want vmexit as soon as interrupts are
>
> allowed to inject ExtINT and we do not want virtual interrupt to be
> delivered. I think the (4) there is exactly for this situation.
One queston: kvm_cpu_has_extint() function check the interrupt from PIC. If PIC is working, APIC must in virtual wire mode. According to spec, when APIC is virtual wire mode, then APIC is totally bypassing. So apic_has_interrupt() and pic_has_interrupt() are mutually exclusive. If kvm_apic_has_interrupt() return true, then kvm_cpu_has_extint will never return true, and vice versa. Am I right? If answer is yes, then we don't check RVI here.
> --
> Gleb.
Best regards,
Yang
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