Re: [Xen-users] Problems converting FC8 HVM guest to PV

[Mark Williamson <mark.williamson@xxxxxxxxxxxx>]

> The *bad* news is, well, bad. The DomU appears to be Ok at first sight,
> but crashes when I run a specific program (wine, which is a
> Windows-on-Unix emulator [yes, I know that's crazy, but I need it for
> testing]). I get a kernel bug:
>
> kernel BUG at include/linux/tracehook.h:369!
> invalid opcode: 0000 [#1]
>
> Should I bother reporting this? The Dom0 appears flakey after this so I
> need to restart the entire machine.

I'm not entirely sure that this is intended to be supported, but it certainly 
shouldn't cause the kernel to BUG out!  So yes, please, it's probably worth 
posting this on the -devel list with a subject lines along the lines 
of "Reproduceable BUG oops in domU (plus subsequent dom0 instability)" so 
that it's recorded.

There may be a similar bug in the Xen Bugzilla but that's still not used very 
effectively these days :-(

What kind of instability do you see in dom0 after this error?  Do you have 
problems with other domUs too?

> I could live with this, by going back to the HVM guest, but this is
> non-trivial. The PV boot messed up various things, and an HVM create
> leaves me locked out of the DomU:
>
> 1 - The console doesn't work (but it never has on my HVM DomU's; I get a
>   "xenconsole: could not read tty from store" error, with nothing useful
> in the qemu log)

That's odd.

You would have to configure the guest to output to the virtual serial port in 
any case, in order to get the xm console to work with an HVM guest.  I'm not 
sure if that's why you're having problems though; I remember seeing that 
error but not what caused it.

> 2 - networking isn't started; I get the normal eth0 startup failed
> message, but there's no subsequent attempt to startup eth1/2/etc

Hmmm.  Well this ought to be fixable...

If you try to manually ifup or ifconfig those interfaces, do they show up at 
all?

Maybe F8 has remove configuration for the virtual hardware which "disappeared" 
when you converted to PV.  It ought to be possible to reconfigure that 
hardware using system-config-network, etc, though...  Ideally there ought to 
be a way of making it retain the config so you can HVM/PV "dual boot".  I'm 
not quite sure what'd be involved in terms of configuring Fedora there, 
though.

> 3 - The sdl window hangs up at the anacron boot message, which is normal
> on the FC8 Dom0 (after FC8 messes up the serial console and inittab).

I've addressed this in another e-mail.

> I'm slowly working my way through this lot, with some (Ok, major)
> irritation. FC8 (or Xen? I don't know) replaced the DomU inittab with
> one it obviously thought was better, which left the DomU in run level 3.
> fixing that has helped. Network next....

That's probably a F8 or virt-install thing.  virt-manager installs graphical 
guests by default; maybe there's an option to virt-install you can tweak to 
change default runlevel?

Cheers,
Mark

-- 
Dave: Just a question. What use is a unicyle with no seat?  And no pedals!
Mark: To answer a question with a question: What use is a skateboard?
Dave: Skateboards have wheels.
Mark: My wheel has a wheel!

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