Xen: finishing the job

“In the mean time, KVM showed up and grabbed much of the
attention. Its path into the mainline was almost blindingly fast,
and many kernel developers were less than shy about expressing
their preference for the KVM approach. More recently, Red Hat has
made things more formal with its announcement of a “virtualization
agenda” based on KVM. Meanwhile, lguest showed up as an easy
introduction for those who want to play with virtualization
code.

“The Xen story is a classic example of the reasons behind the
“upstream first” policy, which states that code should be merged
into the mainline before being shipped to customers. Distributors
rushed to ship Xen, then found themselves supporting out-of-tree
code which, often, was not well supported by its creators. In
particular, published releases of Xen often only supported
relatively old kernels, creating lots of work for distributors
wanting to ship something more current. Now at least some of those
distributors are moving on to other solutions, and high-level
kernel developers are questioning whether, at this point, it’s
worth merging the remaining Xen code at all.”

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