What are the differences between qemu-kvm and qemu-kvm-rhev and all sub-packages?

Environment

• Red Hat Enterprise Linux 6
• Red Hat Enterprise Linux 7
• Red Hat Virtualization
• Red Hat OpenStack

Issue

• I have noticed mention of qemu-kvm and qemu-kvm-rhev. It seems qemu-kvm-rhev offers more features than qemu-kvm, what are the differences?
• How do I get qemu-kvm-rhev?
• Why would I need to install qemu-kvm-rhev on my regular RHEL system?

Resolution

• qemu-kvm is offered in the regular RHEL channels and repositories.

• qemu-kvm-rhev is a special implementation included in the Red Hat Virtualization (RHV) and Red Hat OpenStack (RHOS) products.

• Some newer or advanced virtualization features have been implemented in qemu-kvm-rhev but couldn't be backported to RHEL's qemu-kvm for compatibility reasons.

• The qemu version delivered through RHEL channels is old compared to RHV/OpenStack and hence some performance improvements are missing in RHEL qemu-kvm

• Currently, some major features offered by qemu-kvm-rhev but not offered by qemu-kvm are:

  • Live snapshots and related tasks (e.g.: Live Storage Migration) (Admin. Guide)
  • Streaming, mirroring and live-merge (e.g.: Block-jobs, Live snapshot delete) (Technical Reference Guide)
  • I/O throttling via qemu (Storage quality of service in RHV)
  • I/O Threads (VM Management Guide)
  • Memory hotunplug (ACPI based)
  • Memory hotplug (ACPI based)
  • Support for Windows guests (Certified guest OS on RHEL with KVM, Certified guest OS on RHV/OSP)
  • Several Machine types missing (Certified guest OS on RHEL with KVM, Certified guest OS on RHV/OSP)
  • vhost-user (Content from github.com is not included.QEMU documentation)
  • CPU hotunplug
  • Scaling up to 288 vCPUs (KVM limits, RHV limits)
  • NUMA guest locality for PCIe

• Installing the qemu-kvm-rhev package outside of a RHV or Red Hat Openstack Platform environment is not supported.

NOTE: In Red Hat Enterprise Linux 8, qemu-kvm-rhev is not present. Instead, the Red Hat Enterprise Linux Advanced Virtualization offering is provided in the Red Hat repositories. Similarly to qemu-kvm-rhv, however, Advanced Virtualization is not supported outside of RHV, Red Hat Openstack Platform, and specific Red Hat Enterprise Linux subscriptions.

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