From Fedora Project Wiki

Summary

Combine the kvm and qemu packages into a single package.

Owner

Current status

  • Targeted release: Fedora 11
  • Last updated: 2009-03-26
  • Percentage of completion: 100%

Detailed Description

The QEMU package provides a processor and system emulator which enables users to launch guest virtual machines not only under the same hardware platform as the host machine, but also dramatically different hardware platforms. For example, QEMU can be used to run a PPC guest on a x86 host. QEMU dynamically translates the machine code of the guest architecture into the machine code of the host architecture.

KVM provides kernel support for running guests of the same architecture as the host. Guests run directly on the hardware with out any translation needed by the host, allowing much higher levels of performance to be attained. QEMU can now use the KVM kernel support for higher performance virtualization.

Currently, there is both a qemu package and kvm package. The kvm package's source is a fork of the QEMU source, but KVM regularily re-bases to the latest QEMU source and merging of KVM support into the QEMU code base is actively under-way. The medium term plan is for the KVM fork of QEMU to go away.

In anticipation of this, the package maintainers feel it would be a good idea to merge the packages now. This is to be done as follows:

  1. The qemu package is built using the kvm codebase.
  2. The qemu source package provides a sub-package for each group of target architectures - qemu-system-x86, qemu-system-ppc, qemu-system-sparc etc.
  3. The qemu-user sub-package contains the various user mode emulators.
  4. The qemu-common package contains BIOS binaries, documentation etc.
  5. The kvm package is obsoleted by qemu-system-x86 .
  6. A qemu meta-package requires all the different target sub-packages.

The qemu package previously contained binary BIOS images which were copied directly from the upstream release tarball without rebuilding from source. As part of the package merge, this long-standing issue is resolved by splitting those images into their own packages which are built from source - bochs-bios, vgabios and openbios.

Benefit to Fedora

A single package is far more maintainable than multiple packages. Any bug fixes or security errata involves much less work.

This change will have to be made eventually once the merge happens upstream. Doing the package merge now means we reap the benefits earlier.

Scope

No changes are required outside of the changes to the two packages in question.

Comps could be update to pull in qemu-system-x86 rather than kvm, but either works fine.

The kvm package needs to be blocked from rawhide.

The kvm bugzilla product's rawhide version needs removing. Bugs need migrating.

How To Test

Try updating or installing the pre-merge packages using e.g. yum update kvm. Check that updating kvm results in the qemu-system-x86 package being installed and that updating qemu pulls in the various sub-packages.

Aside from the package updating issue, this feature should be tested as any kvm or qemu upgrade. Test existing guest virtual machines or install new guests using the package and check they run correctly.

User Experience

No user visible change is expected. Users should be able to run guests in the very same way they did before.

The primary benefit to users is that the qemu package will no longer lag behind the kvm package.

Dependencies

There hadn't been a QEMU release in over a year (since 0.9.1). However, upstream recently released 0.10 which helps us to ship an actual released tarball rather than an arbitrary development snapshot.

Since we are building both QEMU and KVM from a kvm-userspace tarball, we need a KVM release based on the QEMU 0.10.x series. This is planned by the upstream KVM maintainer in the short term. In the meantime we're shipping a snapshot of KVM git.

Contingency Plan

No real contingency is required. If the change can't made in time for release, the status quo will remain.

Regressions may be introduced versus the current QEMU 0.9.1 release, but we don't consider that rolling back to a previous release will be an option. QEMU upstream is very active, so we expect any unanticipated regressions would be resolved quickly. This situation isn't really impacted by the merge.

Documentation

Release Notes

Fedora 11 includes a merge of the qemu and kvm RPMs. The merging of the two codebases continues upstream, but the Fedora package maintainers have chosen to merge the packages in order reduce the maintainership burden and provide better support.

Comments and Discussion

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