There's been some discussion of this already in the kvm list, but I want to summarize what I've found and also include the qemu-devel list in an effort to find a solution to this problem. Running a netperf test between two kvm guests results in the guest's network interface shutting down. I originally found this using kvm guests on two different machines that were connected via a 10GbE link. However, I found this problem can be easily reproduced using two guests on the same machine. I am running the 2.6.32 level of the kvm.git tree and the 0.12.1.2 level of the qemu-kvm.git tree. The setup includes two bridges, br0 and br1. The commands used to start the guests are as follows: usr/local/bin/qemu-system-x86_64 -name cape-vm001 -m 1024 -drive file=/autobench/var/tmp/cape-vm001- raw.img,if=virtio,index=0,media=disk,boot=on -net nic,model=virtio,vlan=0,macaddr=00:16:3E:00:62:51,netdev=cape-vm001-eth0 - netdev tap,id=cape-vm001-eth0,script=/autobench/var/tmp/ifup-kvm- br0,downscript=/autobench/var/tmp/ifdown-kvm-br0 -net nic,model=virtio,vlan=1,macaddr=00:16:3E:00:62:D1,netdev=cape-vm001-eth1 - netdev tap,id=cape-vm001-eth1,script=/autobench/var/tmp/ifup-kvm- br1,downscript=/autobench/var/tmp/ifdown-kvm-br1 -vnc :1 -monitor telnet::5701,server,nowait -snapshot -daemonize usr/local/bin/qemu-system-x86_64 -name cape-vm002 -m 1024 -drive file=/autobench/var/tmp/cape-vm002- raw.img,if=virtio,index=0,media=disk,boot=on -net nic,model=virtio,vlan=0,macaddr=00:16:3E:00:62:61,netdev=cape-vm002-eth0 - netdev tap,id=cape-vm002-eth0,script=/autobench/var/tmp/ifup-kvm- br0,downscript=/autobench/var/tmp/ifdown-kvm-br0 -net nic,model=virtio,vlan=1,macaddr=00:16:3E:00:62:E1,netdev=cape-vm002-eth1 - netdev tap,id=cape-vm002-eth1,script=/autobench/var/tmp/ifup-kvm- br1,downscript=/autobench/var/tmp/ifdown-kvm-br1 -vnc :2 -monitor telnet::5702,server,nowait -snapshot -daemonize The ifup-kvm-br0 script takes the (first) qemu created tap device and brings it up and adds it to bridge br0. The ifup-kvm-br1 script take the (second) qemu created tap device and brings it up and adds it to bridge br1. Each ethernet device within a guest is on it's own subnet. For example: guest 1 eth0 has addr 192.168.100.32 and eth1 has addr 192.168.101.32 guest 2 eth0 has addr 192.168.100.64 and eth1 has addr 192.168.101.64 On one of the guests run netserver: netserver -L 192.168.101.32 -p 12000 On the other guest run netperf: netperf -L 192.168.101.64 -H 192.168.101.32 -p 12000 -t TCP_STREAM -l 60 -c -C -- -m 16K -M 16K It may take more than one netperf run (I find that my second run almost always causes the shutdown) but the network on the eth1 links will stop working. I did some debugging and found that in qemu on the guest running netserver: - the receive_disabled variable is set and never gets reset - the read_poll event handler for the eth1 tap device is disabled and never re-enabled These conditions result in no packets being read from the tap device and sent to the guest - effectively shutting down the network. Network connectivity can be restored by shutting down the guest interfaces, unloading the virtio_net module, re-loading the virtio_net module and re-starting the guest interfaces. I'm continuing to work on debugging this, but would appreciate if some folks with more qemu network experience could try to recreate and debug this. If my kernel config matters, I can provide that. Thanks, Tom -- 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
