On Mon, Jul 30, 2012 at 7:08 PM, Bernd Schubert <bernd.schub...@itwm.fraunhofer.de> wrote: > On 07/30/2012 07:33 PM, Bernd Schubert wrote: >> >> Hello Stefan, >> >> Stefan Hajnoczi <stefanha <at> gmail.com> writes: >>> >>> >>> On Wed, Jan 11, 2012 at 4:18 PM, Bernd Schubert >>> <bernd.schubert <at> itwm.fraunhofer.de> 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. >>>> >>>> >> >> >> sorry for my terribly late reply. As usual I got distracted by too many >> other >> things and then returned the hardware I was running the VMs on. My new >> desktop >> system is better suitable to run kvm and I can easily reproduce it now >> with 3.5 >> on host and guest side. So its not fixed in recent versions yet. >> >> >>>> >>>> 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"? >> >> >> It was definitely off and I can confirm that it also locks up with >> vhost=on and >> vhost=off with 3.5. >> >>> >>> 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. >> >> >> Ah nice, I would have used systemtap, but always wanted to check how to do >> it >> with perf :) >> >> So once the virtio NIC has locked up, I don't get any events from it >> anymore - >> until I remove/re-insert the virtio module (including ifup/ifdown). I will >> try >> to find some time later on this week to look into it again. >> Any further ideas how to proceed (I haven't even checked yet how virtio >> works at >> all...). > > > > I took a quick glance where skb_recv_done is registered at all and traced it > back to vp_find_vqs(). Looking into that function I noticed MSI and so tried > to boot with pci=nomsi. And indeed I guessed it right, with pci=nomsi I > don't get any lockups anymore. > Am I the only one booting kvm-qemu usually with enabled MSI?
MSI enabled is good and is the default with modern qemu-kvm + guest OSes. Michael: Any ideas? Stefan -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
