[Xen-users] Run KVM guest on Xen

[Charles Gonçalves <charles.fg@xxxxxxxxx>]

I have a lot of KVM guests that run a big benchmark that I had to port to Xen for my PHD experiments. I'm trying to test the migration of KVM guests to Xen to see if I avoid to reconfiguring all the system. 

Does anyone have successfully made this kind of migration?

On my tests I couldn't make it work!

Created and KVM guest using libvirt that used qcow disks and have the following configuration : 

<domain type='kvm'>

  <name>test</name>

  <uuid>8b86300d-8279-453e-88c3-958a10182597</uuid>

  <memory unit='KiB'>524288</memory>

  <currentMemory unit='KiB'>524288</currentMemory>

  <vcpu placement='static'>1</vcpu>

  <os>

    <type arch='x86_64' machine='pc-i440fx-xenial'>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>destroy</on_crash>

  <devices>

    <emulator>/usr/bin/kvm-spice</emulator>

    <disk type='file' device='disk'>

      <driver name='qemu' type='qcow2'/>

      <source file='/var/lib/uvtool/libvirt/images/test.qcow'/>

      <target dev='vda' bus='virtio'/>

      <address type='pci' domain='0x0000' bus='0x00' slot='0x04' function='0x0'/>

    </disk>

    <disk type='file' device='disk'>

      <driver name='qemu' type='raw'/>

      <source file='/var/lib/uvtool/libvirt/images/test-ds.qcow'/>

      <target dev='vdb' bus='virtio'/>

      <address type='pci' domain='0x0000' bus='0x00' slot='0x05' function='0x0'/>

    </disk>

    <controller type='usb' index='0'>

      <address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x2'/>

    </controller>

    <controller type='pci' index='0' model='pci-root'/>

    <interface type='network'>

      <mac address='52:54:00:d0:74:26'/>

      <source network='default'/>

      <model type='virtio'/>

      <address type='pci' domain='0x0000' bus='0x00' slot='0x03' function='0x0'/>

    </interface>

    <serial type='pty'>

      <target port='0'/>

    </serial>

    <console type='pty'>

      <target type='serial' port='0'/>

    </console>

    <input type='mouse' bus='ps2'/>

    <input type='keyboard' bus='ps2'/>

    <graphics type='vnc' port='-1' autoport='yes' listen='127.0.0.1'>

      <listen type='address' address='127.0.0.1'/>

    </graphics>

    <video>

      <model type='cirrus' vram='16384' heads='1'/>

      <address type='pci' domain='0x0000' bus='0x00' slot='0x02' function='0x0'/>

    </video>

    <memballoon model='virtio'>

      <address type='pci' domain='0x0000' bus='0x00' slot='0x06' function='0x0'/>

    </memballoon>

  </devices>

</domain>

Then tryied to port the guest out of the box just changing to xen libvirt config file:

<domain type='xen'>

  <name>testmig</name>

  <uuid>8b86300d-8279-453e-88c3-958a10182597</uuid>

  <memory unit='KiB'>524288</memory>

  <currentMemory unit='KiB'>524288</currentMemory>

  <vcpu placement='static'>1</vcpu>

  <bootloader>/usr/lib/xen-4.6/bin/pygrub</bootloader>

  <os>

    <type arch='x86_64' machine='xenpv'>linux</type>

    <cmdline>root=/dev/xvda1 ro (null)</cmdline>

  </os>

  <clock offset='utc' adjustment='reset'/>

  <on_poweroff>destroy</on_poweroff>

  <on_reboot>restart</on_reboot>

  <on_crash>restart</on_crash>

  <devices>

    <disk type='file' device='disk'>

      <driver name='tap' type='qcow'/>

      <source file='/var/lib/uvtool/libvirt/images/test.qcow'/>

      <target dev='xvda1' bus='xen'/>

    </disk>

    <disk type='file' device='disk'>

      <driver name='tap' type='raw'/>

      <source file='/var/lib/uvtool/libvirt/images/test-ds.qcow'/>

      <target dev='xvda2' bus='xen'/>

    </disk>

    <interface type='bridge'>

      <mac address='52:54:00:d0:74:26'/>

      <source bridge='virbr0'/>

    </interface>

    <console type='pty'>

      <target type='xen' port='0'/>

    </console>

  </devices>

</domain>

And nothing, the libvirt says:

root@charles-OptiPlex-7010:/home/charles# virsh -c xen:/// create testmigration.xml 

error: Failed to create domain from testmigration.xml

error: internal error: libxenlight failed to create new domain 'testmig'

Then finally tried to use the xen itself porting the configuration :

root@charles-OptiPlex-7010:/etc/xen# cat testmig.cfg 

#

# Configuration file for the Xen instance testxn4, created

# by xen-tools 4.6.2 on Fri Dec  9 09:38:15 2016.

#

#

#  Kernel + memory size

#

bootloader = '/usr/lib/xen-4.6/bin/pygrub'

vcpus       = '1'

memory      = '512'

#

#  Disk device(s).

#

root        = '/dev/xvda2 ro'

disk        = [

                  'tap:qcow:/var/lib/uvtool/libvirt/images/test.qcow,xvda2,w',

                  'tap:qcow:/var/lib/uvtool/libvirt/images/test-ds.qcow,xvda1,w',

              ]

#

#  Physical volumes

#

#

#  Hostname

#

name        = 'testmig'

#

#  Networking

#

dhcp        = 'dhcp'

vif         = [ 'mac=52:54:00:d0:74:26,bridge=virbr0' ]

#

#  Behaviour

#

_on_poweroff_ = 'destroy'

on_reboot   = 'restart'

on_crash    = 'restart'

Again, no success:

root@charles-OptiPlex-7010:/etc/xen# xl create testmig.cfg

Parsing config from testmig.cfg

libxl: error: libxl_device.c:1269:libxl__wait_for_backend: Backend /local/domain/0/backend/qdisk/0/51760 not ready

libxl: error: libxl_bootloader.c:408:bootloader_disk_attached_cb: failed to attach local disk for bootloader execution

libxl: error: libxl_bootloader.c:279:bootloader_local_detached_cb: unable to detach locally attached disk

libxl: error: libxl_create.c:1144:domcreate_rebuild_done: cannot (re-)build domain: -3

libxl: error: libxl.c:1610:libxl__destroy_domid: non-existant domain 11

libxl: error: libxl.c:1568:domain_destroy_callback: unable to destroy guest with domid 11

libxl: error: libxl.c:1495:domain_destroy_cb: destruction of domain 11 failed

Any help? 

It would save me a LOT of time!

--

Charles F.'. Gonçalves

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