Re: NetBSD and Xen 2.0

[Michael Kukat <michael%unixiron.org@localhost>]

Hi !

On Sat, 11 Dec 2004, Thor Lancelot Simon wrote:
> > I would like to help, but currently, my motivation is... away. I gave up. It
> > doesn't even run on Xen 1.2 currently, and it seems impossible to find the
> > problem. No hints, nothing. Maybe i just have the time and patience for all
>
> I honestly don't know what to tell you.  I am running NetBSD-2.0's xen
> port on several machines, including three of the NetBSD Foundation's
> servers.  It works.  I didn't have any of the problems you're describing.
> I did not have to engage in any of the mysterious black art people on this
> list seem to be advocating such as using shell scripts to adjust the size
> of my kernels; it just worked; and it still does.

Okay, the size problem is no longer present. I tracked down the problem to the
following situation:

i renamed /sbin/init to drop down to ddb. Done on a ThinkPad A31, as here i can
"feel" the CPU load by the temperature of the air flowing out of the machine.
and for me, it seems, that even ddb (which should not really produce much CPU
load when standing at the prompt) creates a _LOT_ of CPU load. The keyboard is
extremely unresponsive, so something, and i assume it's in Xen itself, eats up
all the CPU. I don't know if this is a bug in Xen, but it simply doesn't work
in any way useable. And it seems to be a bit impossible to track down the
problem without debugging Xen itself. As said... this is with Xen 1.2.

As Linux runs in Xen 1.2, this is not purely a Xen problem. But without finding
this bug i don't see very good chances to fix the whole port topic. At least
the downwards compatibility is not given. But it's a hint. I'll try to run
NetBSD on top of Xen 2.0, maybe this is a better point to start and fix 1.2
support also.

> Because I did not have, and cannot reproduce, any of the problems you seem
> to be having, I am at a loss as to how to help you.  But I do know that
> NetBSD/xen works because, to be blunt, I use it myself and I can see it
> working every day.

But Dom0 support for Xen 2.0 is not there. This is a goal to be reached.

> I am disappointed and sorry that it's not working _for you_, but that does
> not support the claim that it does not work _in general_.

It's just what i have seen in 3 different environments now. What should work,
according to the list, didn't work in any way here.

> On another note, I'm confused by this talk of Xen 1.3 -- as far as I know,
> what was to be Xen 1.3 simply became Xen 2.0 when it was released.  The
> hypervisor interfaces are different, the 1.2 interface is basically not
> documented, and I am skeptical at best as to the possibility of supporting
> both hypervisor interfaces in a single kernel. :-(

I already have seen, that some important information about Xen 1.2 just has
disappeared from the servers. Not a good starting point. 1.3? Never heard of.
2.01 is the current stable version, and besides some things not indexed by the
pages, the Xen guys seem to never have known of an 1.2 version :(

Maybe if i have some motivation to look into this again, i'll try everything
with Xen 2.0. I would have been happy to have a starting point the NetBSD way,
as i don't really like Linux. But it seems i have to install one of those
thousand incompatible distributions and plug Xen on top, and from this, i have
to handle it with NetBSD in DomU somewhere.

I also don't know what to say... Porting "real" hardware always was easier,
even without complete documentation :)

...Michael

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