RHEL 6 VM does not detect the virtio disks and fails to boot in Openshift Virtualization.

Solution Verified - Updated

Environment

  • Openshift Container Platform (OCP) 4.xx
  • Openshift Virtualization (OCV) 4.xx
  • virtio_blk virtual disk
  • RHEL 6 guest
  • Migration Toolkit for Virtualization (MTV)

Issue

  • After importing or migrating a RHEL 6 VM to Openshift Virtualization, it fails to boot, sometimes, it shows kernel panic. 
? panic+0xa7/0x18b
? perf_event_exit_task+0xc0/0x340
? do_exit+0x853/0x860
? fput+0x25/0x30
? system_call-after_swapds_0x2/0x152
? do_group_exit+0x58/0xd0
? system_exit_group+0x17/0x20
? system_call_fastpath+0x35/0x3a
? system_call_after_swapgs+0xae/0x152
  • In the dracut rescue shell, it is observed that it does not detect the virtio disk.

Resolution

  • Patch the VM to use the virtio-transitional device models:
$ virtctl stop VM_NAME
$ oc patch vm VM_NAME --type=merge -p '{"spec":{"template":{"spec":{"domain":{"devices":{"useVirtioTransitional":true}}}}}}'
$ virtctl start VM_NAME

Root Cause

  • RHEL 6 does not support the non-transitional virtio device models.

Diagnostic Steps

  • Check if useVirtioTransitional is defined in the VM object:
$ oc get vm VM_NAME -o yaml
  • Check if virtio model used in the disks is 'non-transitional':
$ oc rsh virt-launcher-XXXXX virsh -r dumpxml VM_NAME

    <disk type='block' device='disk' model='virtio-non-transitional'>
      <driver name='qemu' type='raw' cache='none' error_policy='stop' io='native' discard='unmap'/>
      <source dev='/dev/vol-1' index='3'/>
      <backingStore/>
      <target dev='vda' bus='virtio'/>
      <alias name='ua-vol-1'/>
      <address type='pci' domain='0x0000' bus='0x04' slot='0x00' function='0x0'/>
    </disk>
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