Objectives

After completing this section, students should be able to describe the new capabilities introduced in the new Q35 emulation.

Updated QEMU Emulation

The Kernel-based Virtual Machine (KVM) kernel module and the QEMU emulator are the basis of virtualization in Red Hat Enterprise Linux 8. In this release, QEMU can now emulate the Intel Q35 motherboard chipset, which offers a better hardware platform for modern virtualized operating systems.

QEMU now emulates the Intel Q35 chipset and its associated Intel ICH9 (I/O controller hub) chipset.

The previous chipset provided only PCI ports (which are difficult to map to physical PCI-E ports), but the ICH9 chipset provides a PCI Express (PCI-E) bus. This supports PCI-E pass-through by directly mapping a PCI-E port inside the virtual machine to a PCI-E port on the host system.

Select the chipset to emulate when creating the virtual machine. If using the web console, virt-install, or virt-manager, the tool automatically chooses the Q35 chipset when a recent, supported operating system is selected.

For RHEL 7, RHEL 8, Microsoft Windows 2016, and Microsoft Windows 10 virtual machines, QEMU emulates the Q35 chipset. For RHEL 6 virtual machines, QEMU emulates the Intel 440FX chipset. The following screen capture shows the selection of the operating system in the web console.

Figure 8.1: Operating system selection in the web console

When you import a virtual machine from a system with an older version of QEMU, you may have to force the previous Intel 440FX chipset emulation. This is because the virtualized operating system already uses drivers for that chipset. If you choose the Q35 chipset emulation, which presents a new hardware model, the virtualized operating system may not have the appropriate drivers installed to use the emulated hardware.

You get the chipset emulation that a virtual machine uses in its XML file definition, in the os section. The following example shows a virtual machine using the new Q35 chipset emulation.

[user@demo ~]$ virsh dumpxml webserver1
<domain type='kvm' id='5'>
  <name>webserver1</name>
  <uuid>f6fbe32f-ef6c-4d8a-8db0-96551c82444b</uuid>
  <metadata>
    <libosinfo:libosinfo xmlns:libosinfo="http://libosinfo.org/xmlns/libvirt/domain/1.0">
      <libosinfo:os id="http://redhat.com/rhel/8.0"/>
    </libosinfo:libosinfo>
  </metadata>
  <memory unit='KiB'>8388608</memory>
  <currentMemory unit='KiB'>8388608</currentMemory>
  <vcpu placement='static'>1</vcpu>
  <resource>
    <partition>/machine</partition>
  </resource>
  <os>
    <type arch='x86_64' machine='pc-q35-rhel7.6.0'>hvm</type>
    <boot dev='cdrom'/>
    <boot dev='hd'/>
  </os>
...output omitted...

The following example shows a virtual machine using the old Intel 440FX chipset emulation.

[user@demo ~]$ virsh dumpxml myrhel6
<domain type='kvm' id='7'>
  <name>myrhel6</name>
  <uuid>51ffc808-d3d0-4220-adc9-32adea33d218</uuid>
  <metadata>
    <libosinfo:libosinfo xmlns:libosinfo="http://libosinfo.org/xmlns/libvirt/domain/1.0">
      <libosinfo:os id="http://redhat.com/rhel/5.0"/>
    </libosinfo:libosinfo>
  </metadata>
  <memory unit='KiB'>1048576</memory>
  <currentMemory unit='KiB'>1048576</currentMemory>
  <vcpu placement='static'>1</vcpu>
  <resource>
    <partition>/machine</partition>
  </resource>
  <os>
    <type arch='x86_64' machine='pc-i440fx-rhel7.6.0'>hvm</type>
    <boot dev='cdrom'/>
    <boot dev='hd'/>
  </os>
...output omitted...

List the supported chipset emulations with the virsh capabilities command.

[user@demo ~]# virsh capabilities
  <guest>
    <os_type>hvm</os_type>
    <arch name='x86_64'>
      <wordsize>64</wordsize>
      <emulator>/usr/libexec/qemu-kvm</emulator>
      <machine maxCpus='240'>pc-i440fx-rhel7.6.0</machine>
      <machine canonical='pc-i440fx-rhel7.6.0' maxCpus='240'>pc</machine>
      <machine maxCpus='240'>pc-i440fx-rhel7.0.0</machine>
      <machine maxCpus='384'>pc-q35-rhel7.6.0</machine>
      <machine canonical='pc-q35-rhel7.6.0' maxCpus='384'>q35</machine>
...output omitted...

The previous output from a RHEL 8 system shows that QEMU supports both the Q35 and the Intel 440FX chipset emulation. The pc machine type is an alias for the i440FX emulation, and the q35 machine type is an alias for the Q35 emulation.

Figure 8.2: Virtualization overview

The virt Yum module has one stream called rhel and a single default profile.

[user@demo ~]$ yum module list
Name          Stream           Profiles            Summary
virt          rhel [d][e]      common [d]          Virtualization module
...output omitted...

SCSI-3 Persistent Reservations with Virtio-SCSI