UDP problem with virtio...

[Erik Brakkee <erik@brakkee.org>]

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Hi,


I am running a guest that exposes a NFS share to be used by a TViX box. The TViX box is not that advanced and uses NFS over UDP instead of TCP.
What I am seeing is that when I use the virtio network driver, the TViX box cannot mount the filesystem. However, when I use rtl8139 instead, it can.

The problem is easily reproduced:
1. Create a guest that uses a virtio network interface (bridging setup)
2. Expose an NFS share on the guest
3. mount the NFS share using 'mount -o udp host:/share /localdir'
4. verify that the NFS share cannot be mounted.
5. Modify the guest to use rtl8139 device emulation and stop the guest and start it
6. mount the NFS share using 'mount -o udp host:/share /localdir'
7. Verify tha the NFS share can be mounted

Now the bug reporting guidelines say that I should always use the latest KVM version but compiling KVM from source and using that is not really an option. The server is important enough not to mess around with. Therefore, my question is whether this problem has been seen before or not.

My configuration is as follows:

*Host*

centos 6.2
uname -a gives "Linux falcon.fritz.box 2.6.32-220.17.1.el6.x86_64 #1 SMP Wed May 16 00:01:37 BST 2012 x86_64 x86_64 x86_64 GNU/Linux"

KVM software: qemu-kvm-0.12.1.2-2.209.el6_2.5.x86_64

*Guest*

OpenSuSE 11.3
uname -a gives "Linux shikra 2.6.34.7-0.7-default #1 SMP 2010-12-13 11:13:53 +0100 x86_64 x86_64 x86_64 GNU/Linux"

I also see in the instructions I should try running qemu with some alternative switches, but I am not running qemu directly. I am using virt-manager and a domain.xml to configure how qemu runs. How should I modify the domain.xml to help in troubleshooting this issue?

Cheers
   Erik

PS. the domain.xml is attached.






[-- Attachment #2: shikra.xml --]
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<domain type='kvm' id='5'>
  <name>shikra</name>
  <uuid>3a524d9f-a9df-4280-d0d7-e7562a860147</uuid>
  <memory>6291456</memory>
  <currentMemory>6291456</currentMemory>
  <vcpu>8</vcpu>
  <os>
    <type arch='x86_64' machine='rhel6.2.0'>hvm</type>
    <boot dev='hd'/>
  </os>
  <features>
    <acpi/>
    <apic/>
    <pae/>
  </features>
  <clock offset='utc'/>
  <on_poweroff>destroy</on_poweroff>
  <on_reboot>restart</on_reboot>
  <on_crash>restart</on_crash>
  <devices>
    <emulator>/usr/libexec/qemu-kvm</emulator>
    <disk type='block' device='disk'>
      <driver name='qemu' type='raw' cache='none' io='native'/>
      <source dev='/dev/bootdisks/shikra'/>
      <target dev='vda' bus='virtio'/>
      <alias name='virtio-disk0'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x03' function='0x0'/>
    </disk>
    <disk type='block' device='disk'>
      <driver name='qemu' type='raw' cache='none' io='native'/>
      <source dev='/dev/shikraroot/disk'/>
      <target dev='vdb' bus='virtio'/>
      <alias name='virtio-disk1'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x04' function='0x0'/>
    </disk>
    <disk type='block' device='disk'>
      <driver name='qemu' type='raw' cache='none' io='native'/>
      <source dev='/dev/shikradata/disk'/>
      <target dev='vdc' bus='virtio'/>
      <alias name='virtio-disk2'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x05' function='0x0'/>
    </disk>
    <disk type='block' device='disk'>
      <driver name='qemu' type='raw' cache='none' io='native'/>
      <source dev='/dev/shikravcr/disk'/>
      <target dev='vdd' bus='virtio'/>
      <alias name='virtio-disk3'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x07' function='0x0'/>
    </disk>
    <interface type='bridge'>
      <mac address='52:54:00:01:01:01'/>
      <source bridge='br0'/>
      <target dev='vnet4'/>
      <model type='virtio'/>
      <alias name='net0'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x08' function='0x0'/>
    </interface>
    <interface type='network'>
      <mac address='52:54:00:01:01:02'/>
      <source network='default'/>
      <target dev='vnet5'/>
      <model type='virtio'/>
      <alias name='net1'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x09' function='0x0'/>
    </interface>
    <serial type='pty'>
      <source path='/dev/pts/3'/>
      <target port='0'/>
      <alias name='serial0'/>
    </serial>
    <console type='pty' tty='/dev/pts/3'>
      <source path='/dev/pts/3'/>
      <target type='serial' port='0'/>
      <alias name='serial0'/>
    </console>
    <input type='mouse' bus='ps2'/>
    <graphics type='vnc' port='5902' autoport='yes'/>
    <video>
      <model type='cirrus' vram='9216' heads='1'/>
      <alias name='video0'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x02' function='0x0'/>
    </video>
    <hostdev mode='subsystem' type='pci' managed='yes'>
      <source>
        <address domain='0x0000' bus='0x02' slot='0x08' function='0x0'/>
      </source>
      <alias name='hostdev0'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x0a' function='0x0'/>
    </hostdev>
    <hostdev mode='subsystem' type='pci' managed='yes'>
      <source>
        <address domain='0x0000' bus='0x02' slot='0x09' function='0x0'/>
      </source>
      <alias name='hostdev1'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x0b' function='0x0'/>
    </hostdev>
    <memballoon model='virtio'>
      <alias name='balloon0'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x06' function='0x0'/>
    </memballoon>
  </devices>
</domain>