From mboxrd@z Thu Jan  1 00:00:00 1970
From: bugzilla-daemon@bugzilla.kernel.org
Subject: [Bug 42829] New: KVM Guest with virtio network driver loses network
 connectivity
Date: Mon, 27 Feb 2012 22:39:26 GMT
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https://bugzilla.kernel.org/show_bug.cgi?id=42829

           Summary: KVM Guest with virtio network driver loses network
                    connectivity
           Product: Virtualization
           Version: unspecified
    Kernel Version: 3.3.0-rc5
          Platform: All
        OS/Version: Linux
              Tree: Mainline
            Status: NEW
          Severity: high
          Priority: P1
         Component: kvm
        AssignedTo: virtualization_kvm@kernel-bugs.osdl.org
        ReportedBy: stefan.bosak@gmail.com
                CC: avi@redhat.com
        Regression: Yes


Description:
------------
Running KVM guests with virtio network interfaces, the guest will
(probably in some - unidentified - circumstances) stop receiving packets.
A tcpdump on the bugged interface will show only ARP requests being
sent by the server and unanswered.

Possible workarounds:

Temporarily:
- restart network interface in guest

Permanent:
- use e1000 network driver as replacement of virtio_net driver


How to reproduce:
-----------------
1) start KVM guest:
qemu-kvm
-nodefaults
-name vps
-chroot /chroot
-runas kvm
-pidfile /var/run/kvm/vps.pid
-vnc 1.2.3.4:0
-vga std --full-screen
-smp 2 -m 1g -cpu host
-mem-path /hugepages
-mem-prealloc
-kvm-shadow-memory 1g
-enable-kvm
-daemonize
-rtc base=localtime,clock=host,driftfix=none
-balloon virtio
-net nic,model=virtio,vlan=0,macaddr=52:54:00:33:22:11
-net bridge,br=br0,vlan=0
-drive aio=native,index=0,media=disk,cache=none,if=virtio,file=vps.img
-boot order=c,menu=off &

2) generate huge trafic (after few minutes virtio network card crashed):
 from host to guest:
  screen ping 10.8.7.2 -s 65507
  screen iperf -s -i 1 -f M
 from guest to host:
  screen ping 10.8.7.1 -s 65507
  screen iperf -c 10.8.7.2 -i 1 -f M

3) restart guest network interface and repeat step 2) until network crash again

Above situation occurs on (my tests):
host kernel 3.3+
qemu-kvm 1.0+
any guest Linux 2.6+ - 3.3+ kernel
any guest Windows 7+

Same situation described from other users on some forums:
http://bugs.centos.org/view.php?id=5526

http://serverfault.com/questions/362038/
qemu-kvm-virtual-machine-virtio-network-freeze-under-load
(possible, not tested old patch)

Please fix above crashing of virtio_net driver.

Thank you for your time.

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