FWN/Beats/Virtualization

Virtualization

In this section, we cover discussion on the @et-mgmnt-tools-list, @fedora-virt, @fedora-xen-list, and @libvirt-list of Fedora virtualization technologies.

Contributing Writer: Dale Bewley

Enterprise Management Tools List

This section contains the discussion happening on the et-mgmt-tools list

New Release virt-manager 0.6.1

Cole Robinson announced[1] a new virt-manager release, version 0.6.1.

Virtual Machine Manager provides a graphical tool for administering virtual machines for KVM, Xen, and QEmu. Start, stop, add or remove virtual devices, connect to a graphical or serial console, and see resource usage statistics for existing VMs on local or remote machines. Uses libvirt as the backend management API.

New features:

VM disk and network stats reporting (Guido Gunther)
VM Migration support (Shigeki Sakamoto)
Support for adding sound devices to an existing VM
Enumerate host devices attached to an existing VM
Allow specifying a device model when adding a network device to an existing VM
Combine the serial console view with the VM Details window
Allow connection to multiple VM serial consoles
Bug fixes and many minor improvements.

[1] http://www.redhat.com/archives/et-mgmt-tools/2009-January/msg00067.html

New Release virtinst 0.4.1

Cole Robinson announced[1] a new virtinst release, version 0.4.1.

python-virtinst is a module that helps build and install libvirt based virtual machines. Currently supports KVM, QEmu and Xen virtual machines. Package includes several command line utilities, including virt-install (build and install new VMs) and virt-clone (clone an existing virtual machine).

New features:

Add virt-image -> vmx support to virt-convert, replacing virt-pack (Joey Boggs)
Add disk checksum support to virt-image (Joey Boggs)
Enhanced URL install support: Debian Xen paravirt, Ubuntu kernel and boot.iso, Mandriva kernel, and Solaris Xen Paravirt (Guido Gunther, John Levon, Cole Robinson)
Expanded test suite
Numerous bug fixes, cleanups, and minor improvements

[1] http://www.redhat.com/archives/et-mgmt-tools/2009-January/msg00068.html

Fedora Virtualization List

This section contains the discussion happening on the fedora-virt list.

Fedora Virt Status Update

True to his word, Mark McLoughlin posted[1] another weekly update on the status of virtualization development in Fedora. Some highlights included:

F11 Alpha Blockers - Workaround found for "unsynchronized TSC" issue[2] which caused guests on certain hosts to hang or crash.
New release of libvirt coming very soon. It's out now.
The KVM PCI Device Assignment[3] feature for F11 "received a very positive reception from FESCo", and "basic device assignment seems to be working."
"Related to PCI device assignment are Intel VT-d issues that have been reported recently. Basically, on some machines ... VT-d support is causing serious [problems] and, in one case, data loss."
New F11 feature page created for sVirt.[4] "sVirt integrates SELinux with the Fedora virtualization stack".
New patches[5] from Jeremy Fitzhardinge reduce the overhead of enabling paravirt_ops on bare-metal by 75% in testing.
Bug count climbed from 186 to 191.

[1] http://www.redhat.com/archives/fedora-virt/2009-January/msg00063.html

[2] https://bugzilla.redhat.com/475598

[3] http://fedoraproject.org/wiki/Features/KVM_PCI_Device_Assignment

[4] http://fedoraproject.org/wiki/Features/SVirt_Mandatory_Access_Control

Fedora Xen List

This section contains the discussion happening on the fedora-xen list.

Xen Users Future on Fedora

Evan Lavelle might have struck a nerve when wondering[1] if those who have invested years in xen on Fedora have been "shafted". "Xen isn't flavour of the month around here, but I assumed there were good reasons for that. Now, rather belatedly, I've found" that Red Hat acquired Qumranet and KVM. (FWN #143[2])

Neil Thompson thought[3] not. "Shafted?...I don't think so. We're just in a blip at the moment." Neil pointed out that "RHEL5, which has a number of years left, includes xen - I don't think Red Hat are going to mess their corporate clients around by removing it. The problem with F8 is that the kernel people could no longer drag an obsolete (2.6.21) kernel around just for xen, and decided to concentrate on helping get it into the mainstream kernel. This[4] has taken longer than expected."

Jan ONDREJ was also concerned[5] that, "KVM is still not a replacement for paravirtualized machines and I think fully virtualized KVM will be slower like a paravirtualized XEN."

Richard W.M. Jones countered[6] "KVM is a great replacement for Xen. It's much easier to use for a start -- no more rebooting into a completely separate kernel hypervisor. As long as you have the virtio drivers in the guest, which is the default for all new Linux distros, performance is roughly the same."

Apropos to the topic, but on another list, Mark McLoughlin explained[7] "Para-virtualization isn't always better. KVM uses full virtualization, meaning that it uses the processor's support for virtualization. This means you can run an unmodified guest OS on KVM. If you can modify the guest OS, then KVM does allow you to use paravirtualization for some performance sensitive operations - so e.g. we've got pvclock, pv MMU and virtio devices. Don't get tied up in marketing terminology - try both and decide for yourself which works best for you."

Support for dom0 is targeted[8] for kernel 2.6.29, but the changelogs[9] for the release candidates don't seem to indicate completion yet. Gerd Hoffmann confirmed[10] that "...most of the dom0 stuff missed the boat. Some prelimary stuff might be in though..." adding that "The pv_ops/dom0 kernel has some not-yet debugged storage issues (disk controller either fails after a while or doesn't work at all), which is the major stumbling block right now."

Daniel P. Berrange, of Red Hat Engineering, detailed the history of Xen on Fedora and explained "while it is definitely unfortunate that we don't have a Xen Dom0 kernel in Fedora 9/10, we are *not* trying to shaft anyone & will re-introduce Xen Dom0 kernels to Fedora when they become available." ... "It [is] still hard to say just when these will be accepted upstream, but there is a semi-reasonable [chance] we'll be able to turn Xen Dom0 back on in Fedora 11 kernels."[11]

[1] http://www.redhat.com/archives/fedora-xen/2009-January/msg00031.html

[2] http://fedoraproject.org/wiki/FWN/Issue143#Red_Hat_Acquires_Makers_of_KVM.2C_Qumranet_Inc.

[3] http://www.redhat.com/archives/fedora-xen/2009-January/msg00033.html

[4] http://fedoraproject.org/wiki/Features/XenPvopsDom0

[5] http://www.redhat.com/archives/fedora-xen/2009-January/msg00032.html

[6] http://www.redhat.com/archives/fedora-xen/2009-January/msg00041.html

[7] http://www.redhat.com/archives/et-mgmt-tools/2009-January/msg00063.html

[8] http://wiki.xensource.com/xenwiki/XenParavirtOps

[9] http://www.kernel.org/pub/linux/kernel/v2.6/testing/ChangeLog-2.6.29-rc2 http://www.kernel.org/pub/linux/kernel/v2.6/testing/ChangeLog-2.6.29-rc1

[10] http://www.redhat.com/archives/fedora-xen/2009-January/msg00056.html

[11] http://www.redhat.com/archives/fedora-xen/2009-January/msg00036.html

Migrating Xen DomU to KVM Guest

Talk of the future of Xen on Fedora led to talk of migrating guests to KVM. Fortunately, migrating a virtual machine from Xen to KVM is straight forward. Well, more or less.

Richard W.M. Jones explained[1] "Install a recent Linux kernel in the guest, adjust the [libvirt] configuration file, and reboot." Alternatively, xenner will enable running "the Xen PV guest unchanged (ie. without installing a new guest kernel)."

Ensure the guest kernel is new enough to support virtio network drivers >= 2.6.25
change the domain <type>, <os>, and <emulator> fields[2] - 'virsh edit <domname>'
"tell[3] the host to give the guest a virtio network card - change the NIC <model type='virtio'/>"

Richard finally noted[4] "For newly installed guests, recent anaconda just works everything out for you and puts the correct drivers into initrd." Mark McLoughlin provided the mkinitrd command to build the appropriate initrd in existing guests: 'mkinitrd --with virtio_pci --with virtio_blk -f /boot/initrd-$(kernelversion) $(kernelversion)' "You only need to do this once. After that, if a new kernel is installed while you're booted off a virtio disk, then mkinitrd will include the modules automatically."

Emre Erenoglu noted[5] "You will also need to specify /dev/vdX on the kernel root= line and make sure your init script inside your initrd triggers the virtio drivers at boot so that the /dev/vdX are created."

Mark McLoughlin added[6] a caveat. "the F9 x86_64 xen kernel didn't have support for running 32 bit binaries like grub, so the bootloader would never have been installed into the MBR. That works fine for pygrub, but not with KVM's real BIOS."

Also see this[7] guide to converting to virtio drivers.

[1] http://www.redhat.com/archives/fedora-xen/2009-January/msg00041.html

[2] http://libvirt.org/drvqemu.html

[3] http://www.redhat.com/archives/fedora-xen/2009-January/msg00048.html

[4] http://www.redhat.com/archives/fedora-xen/2009-January/msg00053.html

[5] http://www.redhat.com/archives/fedora-xen/2009-January/msg00058.html

[6] http://www.redhat.com/archives/fedora-xen/2009-January/msg00078.html

[7] http://wiki.libvirt.org/page/Virtio