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Re: Xen

On 02.08.2011 21:30, Julio Merino wrote:
> Xen is a paravirtualization system: it requires changes to the guest
> operating systems, unlike QEMU or VirtualBox which run unmodified
> systems.  NetBSD has built-in support for Xen, while the support for
> Linux has always been distributed as a set of patches (for reasons
> unknown to me).
> This scheme allows for higher performance of the virtual machines.
> I recommend you to read the "Xen and the Art of Virtualization" paper:

Some additions (or corrections ;) ):

- starting with Xen 3 (a few years back), provided you have hardware
assisted virtualization, you do not need to patch guests to run under
Xen. This only applies to guest VMs though, dom0 still needs to know
that it runs with the hypervisor below so it can handle devices.

Paravirtualized drivers remain faster though, as they do not have the
extra overhead implied by emulation.

- Latest Linux revisions (3, maybe 3.1) have the support included in
vanilla kernel, and are not distributed with third party patches. They
were not included before because of technical and political reasons.

Jean-Yves Migeon

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