Features/XenPvopsDom0

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Xen Pvops Dom0

Summary

pvops-based Package-x-generic-16.pngkernel to serve as Dom0 for a Xen-based system. Currently Fedora releases greater than 8 contain the Xen hypervisor and tools, but not a Xen Dom0-capable kernel.

Owner

Current status

In order to implement this feature, it is necessary to get full Xen Dom0 support upstream and in Fedora. The core Dom0 support has been accepted upstream and was released in Linux 2.6.37. Linux 2.6.39 brought support for the Xen network backend driver. Linux 3.0 brought the block backend driver. Linux 3.1 will bring the pci backend driver (for pci passthru).

Open bugs:

Detailed Description

Xen is a hypervisor-based type-1 virtualization solution. The Xen hypervisor requires a standard operating system that runs in a privileged domain, Dom0. The Dom0 operating system provides driver and guest management support to Xen and other guest operating systems running in the DomU domain. Fedora 8 provided a kernel that could serve as a Dom0 guest. However, newer Fedora releases dropped support for Dom0 (although they can run in DomU). The Xen project is presently pushing the features required for a Dom0 Linux kernel upstream. Once these features are available in the mainline kernel, it follows that Fedora could support Xen Dom0.

Benefit to Fedora

Fedora will benefit from a Xen Dom0-capable kernel. Xen has proven to be a competitive virtualization solution in real-world installations. Xen is different enough from KVM that the two technologies could complement each other within the Fedora Project. There are ongoing benchmarks that intend to define the relative performance of the two technologies.

Scope

How To Test

User Experience

Dependencies

Contingency Plan

There is presently some uncertainty as to when the backend driver support that the Dom0 guest provides DomU guests will be upstream. This may make the upstream kernel that is chosen by Fedora 16 or it may not. Regardless, we will have to touch a lot of subsystems, so it makes sense to start early.

Until all of the requisite Xen components are upstream, we can continue to develop this feature using third party kernels. These third party kernels will be configured to be as close as possible to the forthcoming upstream kernel. In addition, Linux 2.6.39 does contain many of the backend drivers. It may be used with configurations that do not require the block backend driver.

If all of the Xen backend drivers don't make Fedora 16, then little is lost. We can continue to test the Dom0 kernel (with a subset of its eventual features) and work on the supporting infrastructure. It would be useful for our effort to have a working Dom0, grubby, etc in Fedora 16 even if other features (most notably the block backend driver) do not make it. In the worst case, we may delay the announcement of the Dom0 feature to Fedora 17, but can include all progress completed in Fedora 16.

Documentation

See also:

In order to configure Rawhide to boot in Dom0:

1. yum install xen.

2. Edit /etc/default/grub to set "GRUB_DEFAULT="Xen 4.1.1". Update your GRUB 2 configuration using: 

grub2-mkconfig -o /boot/grub2/grub.cfg
.

3. Configure a bridge device by setting /etc/sysconfig/network-scripts/ifcfg-virbr0: 

DEVICE=virbr0
TYPE=Bridge
ONBOOT=yes
USERCTL=no
BOOTPROTO=dhcp
NM_CONTROLLED=no

4. Configure eth0 to be a member of the bridge: 

DEVICE=eth0
HWADDR=[XX:XX:XX:XX:XX:XX]
TYPE=Ethernet
ONBOOT=yes
USERCTL=no
BOOTPROTO=none
BRIDGE=virbr0
NM_CONTROLLED=no

5. Reboot and select your Xen kernel in the GRUB 2 boot menu

Release Notes

The Fedora Linux kernel may now provide the basis for a Xen-based virtualization solution. Xen is a hypervisor-based type-1 virtualization platform. The kernel now has the ability to boot in Xen's Dom0, a privileged domain that allows Fedora to provide driver and guest management support to Xen and other non-privileged, guest operating systems.

Comments and Discussion

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