On 13/07/2017 04:53, peng.hao2@xxxxxxxxxx wrote: > > I think what you're seeing is a race like this: > > > > VCPU 0 VCPU 1 > > [qemu] kvm_get_mp_state > > [kvm] kvm_apic_accept_events > > __apic_accept_irq > > set KVM_APIC_SIPI > > [qemu] kvm_get_vcpu_events > > I suspect that sipi_vector is lost when hotplug cpu in some time. > > VCPU0 VCPU1 (hotplug) > [kvm] apic_send_ipi > [kvm] __apic_accept_irq > [kvm] set vcpu1.sipi_vector > [kvm] set KVM_APIC_SIPI > [kvm] wakeup vcpu1 thread [qemu] kvm_put_vcpu_events > [kvm] set vcpu1.sipi_vector=0 > [kvm] kvm_apic_accept_events > [kvm] kvm_vcpu_deliver_sipi_vector(sipi_vector=0) So I suggest the following changes in QEMU: - reorder kvm_get_vcpu_events, then kvm_get_mp_state, then the others. This is just to be safe and ensure that a KVM_APIC_SIPI event is not lost. - don't set KVM_VCPUEVENT_VALID_SIPI_VECTOR unless the mp_state is KVM_MP_STATE_SIPI_RECEIVED (which will only happen for old kernels). - call kvm_put_mp_state after kvm_put_vcpu_events, so that KVM_APIC_SIPI is only set after the sipi_vector is in place. Thanks, Paolo
