First Thougts on Xen

At work, we’ve been using vserver for virtualization for some years now. Due to various reasons, we’re looking at Xen.

I’ve been trying to switch my workstation to use Xen. I’ve enountered a few issues so far. Probably these will go away as I learn the system.

Overall, my greatest gripe is the documentation. It is outdated and just plain wrong far too often. For instance, there’s a place where it says to run “make ARCH=xen xconfig”, but the Xen kernel patches don’t (any more, at least) provide a xen arch.

The next gripe is the very weird kernel build system. Xen doesn’t ship a diff against a kernel tree. They instead ship whole files to extract atop a particular kernel version. Annoying and unwieldy. There is a command to generate a diff, but you have to download the full kernel tree first.

A couple of other gripes: There is little documentation on memory management (can Xen adjust the RAM usage of running VMs?), on 64-bit systems (can you run a 32-bit kernel under a 64-bit hypervisor? how about a 64-bit kernel that supports 32-bit userspace?)

I’m also having trouble with my forcedeth card locking up under Xen.

However, I’ve heard of lots of people having good luck with it so I’m going to keep trying.

But one would think that basic docs could be actually worked on a bit more.

6 thoughts on “First Thougts on Xen

  1. [quote]
    (can you run a 32-bit kernel under a 64-bit hypervisor? how about a 64-bit kernel that supports 32-bit userspace?)
    [/quote]

    Yes, you can. Both.

    With VMX support in your hardware you can even run a 32bit or 64bit Windows under Xen.

    Reply

    Robin Green Reply:

    Last I checked, you [i]couldn’t[/i] run a 32bit kernel on a 64bit Xen, except in VMX mode, which is slower and only supported on the newest processors.

    However, obviously you can run a 32-bit [i]userspace[/i] system on a 64bit kernel.

    Reply

  2. Regarding the Xen Linux build system, you might consider just using the Debian Xen patch and make-kpkg to build a Debian package of a Xen Linux kernel.

    Reply

    John Goerzen Reply:

    That patch is for Xen 2.0.x, and unfortunately isn’t applicable for Xen 3.0.x. It also doesn’t support recent kernels.

    Reply

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