Messages in this thread |  | | Subject | Re: [PATCH 2/3] kvm: x86: do not use KVM_REQ_EVENT for APICv interrupt injection | From | Yang Zhang <> | Date | Fri, 14 Oct 2016 15:37:38 +0800 |
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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.:-)
-- Yang Alibaba Cloud Computing
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