Thanks,MST! :-) I will change the order back and have a test again. On 2014/7/31 22:37, Michael S. Tsirkin wrote: > On Thu, Jul 31, 2014 at 04:31:00PM +0200, Michael S. Tsirkin wrote: >> On Thu, Jul 31, 2014 at 07:47:24PM +0800, Zhangjie (HZ) wrote: >>> [The test scenario]: >>> >>> Doing migration between two Hosts roundly(A->B, B->A) ,after about 20 times, network of the VM is unreachable. >>> There are other 20 VMs in each Host, and they send ipv4 or ipv6 and multicast packets to each other. >>> Sometimes the CPU idle of the Host maybe 0; >>> >>> [Problem description]: >>> >>> I wonder if it was interrupts missing that cause the network unreachable. >>> In the migration process of kvm, source end should suspend, which include steps as follows: >>> 1. do_vm_stop->pause_all_vcpus >>> 2. vm_state_notify-> vhost_net_stop->set_guest_notifiers->kvm_virtio_pci_vq_vector_release >>> 3. vm_state_notify-> vhost_net_stop-> vhost_net_stop_one->OST_NET_SET_BACKEND-> vhost_net_flush_vq-> vhost_work_flush >>> This may cause interrupts missing. Supose the scene that, virtqueue_notify() is called in virtio_net, >>> then the VM is paused. And, just before the portiowrite being handled, eventfd of kvm is released. >>> Then, vhost could not sense the notify, and the tx notify is lost. >>> On the other side, if eventfd of kvm is released just after vhost_notify(), and before eventfd_signal(), then rx signal by vhost is lost. >> >> Could be a bug in userspace: should should cleanups notifiers >> after it stops vhost. >> >> Could you please send this to appropriate mailing lists? >> I have a policy against off-list discussions. > > Also, Jason, could you take a look please? > Looks like your patch a9f98bb5ebe6fb1869321dcc58e72041ae626ad8 > changed the order of stopping the device. > Previously vhost_dev_stop would disable backend and only afterwards, > unset guest notifiers. You now unset guest notifiers while vhost is still > active. Looks like this can lose events? > > > >> -- >> MST > . > -- Best Wishes! Zhang Jie -- 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
