Chapter 19. Virtualization
This chapter lists the most notable changes to virtualization between RHEL 8 and RHEL 9.
19.1. Notable changes to KVM
KVM virtualization is no longer supported on IBM POWER
Red Hat Kernel-based Virtual Machine (KVM) for Red Hat Enterprise Linux 9.0 and later is not supported on IBM POWER hardware.
VM machine types based on RHEL 7.5 and earlier are unsupported
In RHEL 9, virtual machines (VMs) no longer support machine types based on RHEL 7.5 and earlier. These also include
pc-i440fx-rhel7.5.0 and earlier machine types, which were default in earlier major versions of RHEL. As a consequence, attempting to start a VM with such machine types on a RHEL 9 host fails with an
unsupported configuration error. If you encounter this problem after upgrading your host to RHEL 9, see the Red Hat KnowledgeBase.
RHEL 9 still supports the
pc-i440fx-rhel7.6.0 machine type. However, RHEL will remove support for all
i440x machine types in a future major update.
19.2. Notable changes to libvirt
In RHEL 9, the
libvirt library uses modular daemons that handle individual virtualization driver sets on your host. For example, the
virtqemud daemon handles QEMU drivers. This makes it possible to fine-grain a variety of tasks that involve virtualization drivers, such as resource load optimization and monitoring.
In addition, the monolithic libvirt daemon,
libvirtd, has become deprecated. However, if you upgrade from RHEL 8 to RHEL 9, your host will still use
libvirtd, which you can continue using in RHEL 9.
Nevertheless, Red Hat recommends enabling modular
libvirt daemons instead. For instructions, see the Configuring and managing virtualization document.
Note, however, that if you switch to using modular
libvirt daemons, pre-configured tasks that use
libvirtd will stop working.
virsh iface-* commands are now unsupported
virsh iface-* commands, such as
virsh iface-start and
virsh iface-destroy, are no longer supported in RHEL 9. Due to the removal of the
netcf package, the majority of them do not work. To create and modify network interfaces, use
NetworkManager utilities, such as
19.3. Notable changes to QEMU
QEMU no longer includes the SGA option ROM
In RHEL 9, the Serial Graphics Adapter (SGA) option ROM has been replaced by an equivalent functionality in SeaBIOS. However, if your virtual machine (VM) configuration uses the following XML fragament, this change will not affect your VM functionality.
TPM passthrough has been removed
It is no longer possible to assign a physical Trusted Platform Module (TPM) device using the passthrough back end to a VM on RHEL 9. Note that this was an unsupported feature in RHEL 8. Instead, use the vTPM functionality, which uses the emulator back end, and is fully supported.
Other unsupported devices
QEMU no longer supports the following virtual devices:
The Cirrus graphics device. The default graphics devices are now set to
stdvgaon BIOS-based machines and
bochs-displayon UEFI-based machines.
ac97audio device. In RHEL 9,
19.4. Notable changes to SPICE
SPICE has become unsupported
In RHEL 9, the SPICE remote display protocol is no longer supported. On a RHEL 9 host, VMs configured to use SPICE fail to start and instead display an
unsupported configuration error.
Instead of SPICE, Red Hat recommends using alternate solutions for remote display streaming:
For remote console access, use the
VNCprotocol. However, note that certain features available on SPICE are currently unsupported or do not work well on VNC. This includes:
- Smart card sharing from the host to the VM (It is now supported only by third party remote visualization solutions.)
- Audio playback from the VM to the host
- Automated VM screen resizing
- USB redirection from the host to the VM
- Drag & drop file transfer from the host to the VM
- In addition, VNC cannot be used by the GNOME Boxes application. As a consequence, Boxes is currently not available in RHEL 9.
- For advanced remote display functions, use third party tools such as RDP, HP ZCentral Remote Boost, or Mechdyne TGX.
For graphical VMs hosted on RHEL 9, Red Hat recommends using the
virtio-gpu virtual graphics cards.