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Chapter 5. Converting virtual machines to the Q35 machine type

In RHEL 10, the i440fx machine type is deprecated, and will be removed in a future major version of RHEL. In addition, using the q35 machine type provides additional benefits in comparison to i440fx, such as Advanced Host Controller Interface (AHCI) and virtual Input-output memory management unit (vIOMMU) emulation.

Therefore, Red Hat recommends converting your virtual machines (VMs) that use i440fx to use q35 instead. Note that you can also convert VM configurations that you have not defined yet.

Considerations

Changing a machine type of a VM is similar to changing the motherboard on a physical machine. As a consequence, converting the machine type of a VM from i440fx to q35 might, in some cases, cause problems with the functionality of the guest operating system.

Prerequisites

  • A VM on your RHEL 10 host is using the i440fx machine type. To confirm this, use the following command: 

    # virsh dumpxml <vm-name> | grep machine

<type arch='x86_64' machine='pc-i440fx-10.0.0'>hvm</type>
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  • You have backed up the original configuration of the VM, so you can use it for conversion and disaster recovery, if necessary. 

    # virsh dumpxml <vm-name> > <vm-name>-backup.xml
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Procedure for undefined VMs

  1. Adjust the configuration of the VM to use Q35. As the source configuration, use the backup file that you created previously. 

    # cat <vm-name>-backup.xml | virt-xml --edit --convert-to-q35 > <vm-name-q35>.xml
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  2. Define the VM. 

    # virsh define <vm-name-q35>.xml
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Procedure for defined VMs

  1. Adjust the configuration of the VM to use Q35. 

    # virt-xml <vm-name> --edit --convert-to-q35
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  2. If the VM is running, shut it down. 

    # virsh shutdown <vm-name>
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Verification

  1. Display the machine type of the VM. 

    # virsh dumpxml <vm-name> | grep machine

    <type arch='x86_64' machine='q35'>hvm</type>
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  2. Start the VM and check that you can log in to the guest operating system.

Troubleshooting

  • If you are using a Windows guest operating system, and the VM cannot find the boot device after the conversion, boot into safe mode, then reboot the VM.

  • If changing the machine type has made the VM not functional, define a new VM based on the backed-up configuration. 

    # virsh define <vm-name>-backup.xml
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