During the week of Citrix Synergy, much of the Xen community was looking to the news coming out of the show around what Citrix and its ecosystem of partners were doing within the XenServer, XenDesktop, and cloud computing markets. However, there was an interesting event that may have been overlooked by the Xen community during that time. With news coming out about Linux 3.0, it was also announced that all key Xen code had been finally accepted into the Linux mainline kernel after almost eight years since Xen's first release.
For years, Oracle, Citrix, and other members of the Xen.org community have been undertaking numerous efforts to fully integrate the various components of the open source Xen technology into the Linux mainline kernel so that each of the Linux distribution vendors could fully support and enable Xen in their solutions without requiring additional work and effort on their part or that of their users. It is that struggle that seems to have finally reached a conclusion.
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According to the latest news, the Linux mainline tree (2.6.39+) now contains literally every component needed for Linux to run both as a management domain kernel (Dom0) and as a guest (DomU).
Oracle's senior vice president of Linux and virtualization engineering, Wim Coekaerts explained things in a bit more detail within a recent Oracle blog post:
Xen has always used Linux as the management OS (Dom0) on top of the hypervisor itself, to do the device management and control of the virtual machines running on top of Xen. And for many years, next to the hypervisor, there was a substantial linux kernel patch that had to be applied on top of a linux kernel to transform into this "Dom0". This code had to constantly be kept in sync with the progress Linux itself was making and as such caused a substantial amount of extra work that had to be done.