[Planetlab-devel] pl/xen

[David Irwin]

Hi,

There was some discussion on the PL-devel mailing list a month ago
related to running PlanetLab on Xen virtual machines.  We did get this
working; primarily by using a patch from Gerd Hoffmann that enables
kexec for a XenU kernel.  We have experimented with Xen using the
MyPLC software, but, so far, have not used it to add nodes to the
production PlanetLab.

I believe a couple of things must be done by PLC to cleanly enable
Xen.  First, it seems that the AddNode function of the PL API needs a
Xen option.  If Xen is selected then a Xen-compliant PlanetLab kernel
should be distributed to the node.  Second, a kernel with the kexec
patch needs to be available to use in conjunction with the boot CD
iso.  This patched domU Xen kernel can run on vanilla Xen (>=3.0.2).
The PlanetLab kernel **does not** need to be changed, other than I
found that disabling kernel debugging on compile was required.  There
are also some minor changes to scripts required (e.g., to use the Xen
kexec rather than the vanilla Linux kexec).

We can certainly add/remove Xen nodes without these changes, however,
it would compromise PLC's ability to roll out updates to our kernels
(because we would not use PLC-distributed kernels, but our own PL/Xen
kernels).  Given this, we will likely wait for some direction from PLC
before proceeding.

I am planning to write more detailed documentation, however, if anyone
is interested in this now feel free to email.  Also, if others have
made progress with this in the intervening month I would be happy to
compare notes.

Thanks,

David