On 15/01/2015 13:36, Li Kaihang wrote: > This patch fix a external interrupt injecting bug in linux 3.19-rc4. > > GuestOS is running and handling some interrupt with RFLAGS.IF = 0 while a external interrupt coming, > then can lead to a vm exit,in this case,we must avoid inject this external interrupt or it will generate > a processor hardware exception causing virtual machine crash. I do not understand what is happening here. Between the time the processor starts delivering an external interrupt to the VM, and the time it decides to do a vm exit because of an external interrupt in the host, IF becomes 0. What is the cause of the external interrupt? Why does IF become 0? > Now, I show more details about this problem: > > A general external interrupt processing for a running virtual machine is shown in the following: > > Step 1: > a ext intr gen a vm_exit How did the external interrupt cause the IDT-vectoring information field to be set? External interrupts for the host are not among the causes listed in "27.2.3 Information for VM Exits During Event Delivery". > --> vmx_complete_interrupts --> __vmx_complete_interrupts --> case INTR_TYPE_EXT_INR: kvm_queue_interrupt(vcpu, vector, type == INTR_TYPE_SOFT_INTR); > > Step 2: > kvm_x86_ops->handle_external_intr(vcpu); Why is this relevant? The external interrupt is a vectored event, so it sets VM-exit interruption information (27.2.2 Information for VM Exits Due to Vectored Events). It doesn't set the IDT-vectoring information field. Paolo > Step 3: > get back to vcpu_enter_guest after a while cycle,then run inject_pending_event > > Step 4: > if (vcpu->arch.interrupt.pending) { > kvm_x86_ops->set_irq(vcpu); > return 0; > } > > Step 5: > kvm_x86_ops->run(vcpu) --> vm_entry inject vector to guestos IDT > > for the above steps, step 4 and 5 will be a processor hardware exception if step1 happen while guestos RFLAGS.IF = 0, that is to say, guestos interrupt is disabled. > So we should add a logic to judge in step 1 whether a external interrupt need to be pended then inject directly, in the process, we don't need to worry about > this external interrupt lost because the next Step 2 will handle and choose a best chance to inject it by virtual interrupt controller. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html