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SubjectRe: [PATCH 2/3] kvm: x86: do not use KVM_REQ_EVENT for APICv interrupt injection
On 2016/9/28 19:50, Paolo Bonzini wrote:
> On 28/09/2016 13:40, Wu, Feng wrote:
>> IIUIC, the issue you describe above is that IPI for posted-interrupts may be
>> issued between
>> vcpu->mode = IN_GUEST_MODE;
>> and
>> local_irq_disable();
>> But if that really happens, we will call kvm_vcpu_kick() in
>> vmx_deliver_posted_interrupt(), hence the vcpu->mode will be changed
>> to EXITING_GUEST_MODE, then we will goto cancel_injection in
>> vcpu_enter_guest, so the posted-interrupt will be delivered to guest
>> in the next vmentry. Seems I cannot see the problem. Do I miss something?
> No, if that happens kvm_trigger_posted_interrupt returns true, hence
> kvm_vcpu_kick is not called. With the fix, the IPI is processed as soon
> as the guest enters non-root mode, and the interrupt is injected.
> The other issue occurs when the IPI is sent between
> kvm_x86_ops->hwapic_irr_update(vcpu,
> kvm_lapic_find_highest_irr(vcpu));
> and
> vcpu->mode = IN_GUEST_MODE;
> In this case, kvm_vcpu_kick is called but it (correctly) doesn't do
> anything because it sees vcpu->mode == OUTSIDE_GUEST_MODE. Then the
> guest is entered with PIR.ON, but the PI interrupt is not pending and
> hence the interrupt is never delivered to the guest. The fix for this
> is to move the RVI update after IN_GUEST_MODE. Then the source CPU uses
> the posted interrupt IPI instead of kvm_cpu_kick, and everything works.

Please ignore my previous reply. It seems you already aware the issue
and get the resolution to fix it.:-)

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