[Crash-utility] Xen Dumping - Expectations

[Dave Anderson]

As it turns out, everything is working as expected, except
for the "WARNING: possibly bogus exception frame" x86_64
messages.  They are harmless, but I will look into whether
they are still viable warnings.

The problem reported with the truncated address stuff on
the initial "bt" lines is solely due to running crash over a vnc.
There's nothing I can do about that.

And FWIS, there is a "xm dump -L" for a live system dump, and
an "xm dump -C" for crashing the system.  But they both
end up with similar (indistinguishable) coredump files.

Thanks,
  Dave


Dave Anderson wrote:

> Joshua Giles wrote:
>
> > Not quite sure if this or the kdump list is appropriate for this
> > discussion, but I will start here...
> >
>
> Why kdump?
>
> >
> > 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?
>
> >
> >
> > `crash /usr/lib/debug/lib/modules/2.6.18-1.2714.el5xen/vmlinux /xen/dump/Live_Dump`
> >
> > "WARNING: possibly bogus exception frame
> > WARNING: possibly bogus exception frame
> > WARNING: possibly bogus exception frame
> > WARNING: possibly bogus exception frame
> > WARNING: possibly bogus exception frame
> > WARNING: possibly bogus exception frame
> > WARNING: possibly bogus exception frame
> > WARNING: possibly bogus exception frame
> > WARNING: possibly bogus exception frame
> > WARNING: possibly bogus exception frame
> > WARNING: possibly bogus exception frame
> > WARNING: possibly bogus exception frame
> > WARNING: possibly bogus exception frame
> > WARNING: possibly bogus exception frame
> > WARNING: possibly bogus exception frame
> > WARNING: possibly bogus exception frame
> > WARNING: possibly bogus exception frame
> > WARNING: possibly bogus exception frame
> > WARNING: possibly bogus exception frame
> > WARNING: possibly bogus exception frame
> > WARNING: possibly bogus exception frame
> >       KERNEL: /usr/lib/debug/lib/modules/2.6.18-1.2714.el5xen/vmlinux
> >     DUMPFILE: /xen/dump/Live_Dump
> >         CPUS: 1
> >         DATE: Mon Oct 16 11:46:02 2006
> >       UPTIME: 00:07:12
> > LOAD AVERAGE: 0.00, 0.02, 0.00
> >        TASKS: 67
> >     NODENAME: dhcp78-103.lab.boston.redhat.com
> >      RELEASE: 2.6.18-1.2714.el5xen
> >      VERSION: #1 SMP Mon Oct 2 17:26:27 EDT 2006
> >      MACHINE: x86_64  (3200 Mhz)
> >       MEMORY: 264 MB
> >        PANIC: ""
> >          PID: 0
> >      COMMAND: "swapper"
> >         TASK: ffffffff804c5ae0  [THREAD_INFO: ffffffff805de000]
> >          CPU: 0
> >        STATE: TASK_RUNNING (ACTIVE)
> >      WARNING: panic task not found
> >
> > crash>crash> bt
> > crash>
> > crash> ffffff805dff68] raw_safe_halt at ffffffff8026c989
> > crash> ffffff805dff88] xen_idle at ffffffff8026a04d
> > crash> ffffff805dff98] cpu_idle at ffffffff80248e4d"
> >
> > *WARNINGS, WARNINGS, WARNINGS (no such problem like this for i386.)
> > *The output of bt doesn't actually work as expected.  You have to hit
> > carriage return a couple times before you see anything.
> >
> > #####i386#############################################################
> > crash /usr/lib/debug/lib/modules/2.6.18-1.2714.el5xen/vmlinux /xen/dump/live_dump
> > This GDB was configured as "i686-pc-linux-gnu"...
> >
> >       KERNEL: /usr/lib/debug/lib/modules/2.6.18-1.2714.el5xen/vmlinux
> >     DUMPFILE: /xen/dump/live_dump
> >         CPUS: 1
> >         DATE: Mon Oct 16 11:47:28 2006
> >       UPTIME: 00:08:30
> > LOAD AVERAGE: 0.00, 0.04, 0.03
> >        TASKS: 68
> >     NODENAME: dhcp78-115.lab.boston.redhat.com
> >      RELEASE: 2.6.18-1.2714.el5xen
> >      VERSION: #1 SMP Mon Oct 2 17:40:51 EDT 2006
> >      MACHINE: i686  (3200 Mhz)
> >       MEMORY: 264 MB
> >        PANIC: ""
> >          PID: 0
> >      COMMAND: "swapper"
> >         TASK: c0674a60  [THREAD_INFO: c07a3000]
> >          CPU: 0
> >        STATE: TASK_RUNNING (ACTIVE)
> >      WARNING: panic task not found
> >
> > crash> bt
> >
> > crash>
> > crash> 7a3fa8] hypercall_page at c04013a7
> > crash> 7a3fb8] xen_idle at c0402bdb
> > crash> 7a3fc0] cpu_idle at c0402d02
> > crash>
> >
> > *The output of bt doesn't actually work as expected.  You have to hit
> > carriage return a couple times before you see anything and the addresses
> > are partially visible...
> > *panic task not found?
> >
> > Are these known problems with crash and/or xen?
>
> No -- but it's never been tested with this new "xm dump-core" facility.
>
> > Is xen dumping
> > supported on x86, x86_64, ppc, ia64?
>
> x86 and x86_64 only -- ia64 is still TBD.
>
> > 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
>
> Anyway, when you get the time, please stop by.
>
> Thanks,
>   Dave
>
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