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  1. OpenShift Virtualization
  2. CNV-42700

Cannot add Virtio-SCSI disks on VM having preference set to rhel.9 virtualmachineclusterpreference

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    • Icon: Bug Bug
    • Resolution: Done-Errata
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    • CNV v4.16.1
    • CNV v4.14.8, CNV v4.15.2
    • CNV Infrastructure
    • None
    • CNV Infra 256
    • High
    • No

      Description of problem:

      The rhel.9  cluster preference have preferredDiskDedicatedIoThread set to "true":

      # oc get VirtualMachineClusterPreference  rhel.9 -o yaml |yq '.spec.devices'
      preferredDiskBus: virtio
      preferredDiskDedicatedIoThread: true     <===
      preferredInterfaceModel: virtio
      preferredRng: {}

      It's not possible to add SCSI disk to the virtual machines using the above preference, because it will add "dedicatedIOThread: true" for all the disks and will fail with error below for SCSI disk:

      Error "IOThreads are not supported for disks on a scsi bus" for field "spec.template.spec.domain.devices.disks.domain.devices.disks[1]".

      In 4.14, where this Webhook rejection was not available (https://issues.redhat.com/browse/CNV-34292), it will allow to add the disk, but will fail during the VM startup:

       

      oc get vm rhel-9-skilled-cod -o yaml |yq '.spec.preference,.spec.template.spec.domain'
      kind: virtualmachineclusterpreference
      name: rhel.9
      revisionName: rhel-9-skilled-cod-rhel.9-0ab600fd-4a12-40ca-bd2b-a6065e9c830f-1
      devices:
        disks:
          - disk:
              bus: scsi
            name: disk-pregnant-muskox
      machine:
        type: pc-q35-rhel9.2.0
      resources: {}
      oc get vmi rhel-9-skilled-cod -o yaml |yq '.spec.domain.devices.disks[0]'
      dedicatedIOThread: true
      disk:
        bus: scsi
      name: disk-pregnant-muskox
      {"component":"virt-launcher","kind":"","level":"error","msg":"Failed to sync vmi","name":"rhel-9-skilled-cod","namespace":"nijin-cnv","pos":"server.go:202","reason":"virError(Code=67, Domain=10, Message='unsupported configuration: IOThreads not available for bus scsi target sda')","timestamp":"2024-06-05T15:36:11.954725Z","uid":"1f226cf1-ce5f-4e8a-8557-155bf4d6d7ed"}

       

      Version-Release number of selected component (if applicable):

      OpenShift Virtualization   4.15.2

      How reproducible:

      100%

      Steps to Reproduce:

      1. Create a VM from UI using instance and select rhel9 volume. 
      2. Once created, try to add a SCSI disk to the VM. It fails with error below:
      
      Error "IOThreads are not supported for disks on a scsi bus" for field "spec.template.spec.domain.devices.disks.domain.devices.disks[1]".
      
      

      Actual results:

      Cannot add Virtio-SCSI disks on VM having preference set  to rhel.9 virtualmachineclusterpreference

      Expected results:

      dedicatedIOThread: true shouldn't be passed for SCSI disks

      Additional info:

       

            rhn-support-lyarwood Lee Yarwood
            rhn-support-nashok Nijin Ashok
            Roni Kishner Roni Kishner
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              Created:
              Updated:
              Resolved: