On Wed, Jan 11, 2012 at 4:18 PM, Bernd Schubert <bernd.schubert@xxxxxxxxxxxxxxxxxx> wrote: > On 01/11/2012 05:04 PM, Stefan Hajnoczi wrote: >> Try pinging the host's IP address from inside the guest. Run tcpdump >> on the guest's tap interface from the host and observe whether or not >> you see any packets being sent from the guest. > > > Seems arp requests are still going out, but then don't go in: > > 17:16:21.202547 ARP, Reply 192.168.123.1 is-at 00:25:90:38:09:cd (oui > Unknown), length 28 > 17:16:21.538724 ARP, Request who-has squeeze1 tell squeeze3, length 28 > 17:16:21.539026 ARP, Reply squeeze1 is-at 52:54:00:12:34:11 (oui Unknown), > length 28 > 17:16:22.200912 ARP, Request who-has 192.168.123.1 tell squeeze3, length 28 Okay, so it seems networking from the tap device and beyond is fine. >> rmmod virtio_net inside the guest and then modprobe virtio_net again. >> See if network connectivity is restored (remember to rerun DHCP or >> whatever, if necessary). > > > Yep, that makes it work again. But probably is not the real solution ;) It's just another piece of information which helps debug this :). At least nothing has wedged itself into an unrecoverable state. When you said the problem happens without vhost, did you explicitly run vhost=off? Or did you just omit "vhost=on"? This sounds like a guest kernel/driver issue. I recommend testing git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git in the guest to see if this has already been fixed. If you have the -dbg RPMs installed it may be possible to insert a probe into the virtio_net kernel module and observe receive interrupts. This does require the right kernel CONFIG_ but you might already have it enabled: $ sudo perf probe --add skb_recv_done $ sudo perf record -e probe:skb_recv_done -a ...send some packets to the guest... ^C $ sudo perf script If you see no skb_recv_done events then the guest driver is not receiving a notification when packets are received. You can find more about how to use perf-probe(1) at http://blog.vmsplice.net/2011/03/how-to-use-perf-probe.html. Stefan -- 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
