** Description changed: Binary package hint: kvm ===================================== SRU justification: 1. Impact: Networking can freeze for a while when VMs are started or stopped. - 2. How addressed: a patch was cherry-picked from upstream, which makes sure to assign the libvirt bridge a low enough macaddr that the VM's macaddr will be higher, so that the bridge does not change macaddrs, which is the cause of the hangs. + 2. How addressed: a patch was cherry-picked from upstream, which carefully chooses high enough macaddr for newly created network interfaces so that the bridge does not change macaddrs, which is the cause of the hangs. 3. Patch: see the linked bzr tree 4. Regression potential: very unlikely as this patch is upstream, and only affects the mac address chosen for the libvirt brige. 5. To reproduce: Define a VM with a macaddr lower than the bridge's. Start the VM. ===================================== Serious networking problems with KVM running a Windows XP x64 host using bridged networking. This may be a KVM bug, or a bridged-networking or ethernet driver bug; I unfortunately don't have the skills to tell the difference but will do what I can to help pinpoint the problem. My Setup: - Lucid 64bit installed on dual quad-core (Intel) Dell Precision R710, 32Gb RAM. - One KVM instance running Windows XP x64 with 16Gb RAM, using bridged networking. Symptoms occur with both standard "-net nic" KVM network drivers (rtl8139?) and virtio network drivers on Windows. Either way I am also using "-net tap" so I can get out to the real network. - I'm starting KVM from the command line instead of using libvirt & virt-manager, because I need to specify sockets/cores/threads for my CPU. Otherwise Windows XP only uses 2 CPUs. I don't think this is relevant but who knows. The Problem: The KVM windows image starts up fine, and at first works properly. But after a very short duration, usually less than two minutes, the networking freezes up. Can't get to the internet, can't access local shares, nothing. Sometimes it magically comes back; sometimes it's gone forever. An interesting, possibly related detail: If I shut down the Windows image, the host machine's networking freezes up for many seconds just as the image is exiting. After the exit is complete and KVM is completely shut down, I can ssh or VNC back into the host machine again without problems. So, after restarting the KVM image I try running the "iperf" network performance tool in two modes. 1) From a separate PC on my LAN, I can run iperf between the Lucid *host* and that PC, and never have any problems. I can consistently get 800 Mbits/sec up and 200 MBits/sec down. (I've run it about 50 times) 2) From the separate PC to the KVM Windows image running on the Lucid host: - it sometimes runs successfully with 130Mbit/sec in both directions; - other times gets just 25-40Mbit/sec; - and sometimes it fails completely with the error message "write failed: Connection reset by peer. read on server close failed: Connection reset by peer". What can I do to help pinpoint this bug? My hunch is the error is in the bridging or the ethernet driver, but I don't know how to test that since I only use bridging for KVM clients! Any ideas on what I can do? I really want to help diagnose this.
-- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/584048 Title: kvm images losing connectivity w/bridged network -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
