[Pkg-xen-devel] Several xen problems in Debian Etch

[Ian Jackson]

Christian Schneider writes ("Re: [Pkg-xen-devel] Several xen problems in Debian Etch"):
> On Saturday 24 November 2007 10:01, Bastian Blank wrote:
> > On Sat, Nov 24, 2007 at 01:10:01AM +0100, Christian Schneider wrote:
> > > - A "shutdown" of a HVM Windows XP domU results in a "destroy".
> > > This may not be a real xen, but a Windows problem, though a
> > > workaround or at least a warning in xen's documentation (man page,
> > > xm help, or something like that) would be great.
> >
> > The default behaviour is "destroy".
> 
> So for HVM domUs "xm shutdown" is the same as "xm destroy"??? There 
> should be a warning that shutdown does a destroy or something like 
> that. This behaviour is not healthy for the filesystems of the domU.

I think you may be talking at cross purposes.

I think Bastian is referring to the fact that if you
`xm shutdown <domain>', by default when the domain has finished
shutting down the `ended' domain will then be thrown away.  This is
controlled by the `on_shutdown' parameter in xmdomain.cfg.

But I think Christian is saying that `xm shutdown <XP guest>' causes
the guest to be immediately terminated as if `xm destroy' had been
used - that is, the guest is not notified to shut itself down but is
instead terminated with prejudice.

The problem here is that only guests with PV drivers are able to
receive the notification that the host wishes to shut them down.  For
an HVM domain when a clean shutdown is requested, xend looks to see
whether the domain is using PV drivers and if not it will immediately
perform a `remote shutdown' on the domain which AFAICT basically
amounts to issuing the `shutdown completed' call on the guest's
behalf.  The result is very similar to a destroy.

Arguably it is a mistake that `xm shutdown' does not fail in this
situation.  The domain is not capable of being told to shut itself
down, so it would be better to let the caller know.

If you want to cleanly shut down a Windows guest without appropriate
PV drivers (which aren't generally Freely available I think) you will
need to find your own way to instruct the guest operating system to do
a clean shutdown.

Ian.