[Crash-utility] Xen Dumping - Expectations

[Dave Anderson]

Jarod Wilson wrote:

> On Mon, 2006-10-16 at 14:02 -0400, Dave Anderson wrote:
> > > I've been playing with xen dumping on x86_64 and x86 (RHEL5 20061006.2);
> > > The following is a simple crash session on x86_64 (using "xm dump-core
> > > -L"):
> >
> > Interesting.  It kind of looks like there's something different about the
> > corefile contents when using "xm dump-core" as opposed to forcing
> > a "real" crash, i.e., such as when using sysrq-c?
>
> Hrm, yeah, interesting... Last I tried with an actual forced crash of a
> guest, everything looked as expected when I spun up crash on the
> resulting core file. Of course, its been two or three weeks now, so it
> coulda changed. ;)

Actually, my best guess is that crash it just getting confused trying
to handle the "panic" task -- it presumes that there is one since it's
a xen "coredump" file, but in this case, there really isn't one.  The new
"xm core-dump -L" facility is taking a "live dump" of a live system without
forcing a panic.  (I'm not sure what other flags besides "-L" exist,
and what they would do differently...)

Dave


>
>
> > > Is xen dumping
> > > supported on x86, x86_64, ppc, ia64?
> >
> > x86 and x86_64 only -- ia64 is still TBD.
>
> ia64... yeah... I can't even get a xen guest to install w/o panicking
> dom0... :(
>
> > > Can anyone point me to docs that
> > > talk about xen dumping (e.g. internal/external wiki?)
> >
> > None that I'm aware of...
> >
> > The best thing that you can do is come over to my office,
> > and we'll get to the bottom of this.  In the meantime, it would
> > be interesting to know whether the behavior above is the
> > same when you:
> >
> > 1. log into the domU
> > 2. echo c > /proc/sysrq-trigger
>
> And another way to do it: if your domU has sysrqs enabled, then you can
> issue 'xm sysrq <domU name> c' from the dom0. That's actually what will
> get used for the rhts xen dumping test I've been meaning to finally
> write for some time now... :)
>
> --
> Jarod Wilson
> jwilson at redhat.com
>
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