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Re: [Xen-devel] [PATCHv10 0/9] Xen: extend kexec hypercall for use with pv-ops kernels

On 11/09/13 14:18, Daniel Kiper wrote:
On Thu, Nov 07, 2013 at 10:16:51PM +0100, Daniel Kiper wrote:
On Wed, Nov 06, 2013 at 02:49:37PM +0000, David Vrabel wrote:
The series (for Xen 4.4) improves the kexec hypercall by making Xen
responsible for loading and relocating the image.  This allows kexec
to be usable by pv-ops kernels and should allow kexec to be usable
from a HVM or PVH privileged domain.

I have now tested this with a Linux kernel image using the VGA console
which was what was causing problems in v9 (this turned out to be a
kexec-tools bug).

The required patch series for kexec-tools will be posted shortly and
are available from the xen-v7 branch of:
In general it works. However, quite often I am not able to execute panic
kernel. Machine hangs with following message:

(XEN) Domain 0 crashed: Executing crash image

gdb shows:

(gdb) bt
#0  0xffff82d0801a0092 in do_nmi_crash (regs=<optimized out>) at crash.c:113
#1  0xffff82d0802281d9 in nmi_crash () at entry.S:666
#2  0x0000000000000000 in ?? ()

Especially second bt line scares me... ;-)))

I have not been able to identify why NMI was activated because
stack is completely cleared. I tried to record execution in gdb
but it stops with following message:

cpumask_clear_cpu (dstp=0xffff82d0802f7f78 <call_data+24>, cpu=0)
     at /srv/dev/xen/xen_20130413_20131107.kexec/xen/include/xen/cpumask.h:108
108             clear_bit(cpumask_check(cpu), dstp->bits);
Process record: failed to record execution log.

Do you know how to find out why NMI was activated?

I am able almost always reproduce this issue doing this:
   - boot Xen,
   - load panic kernel,
   - echo c > /proc/sysrq-trigger,
   - reboot from command line,
   - boot Xen,
   - load panic kernel,
   - echo c > /proc/sysrq-trigger.
I am not able to reproduce this on real hardware. Sorry for confusion.

Hence, for whole Xen kexec/kdump series:

Reviewed-by: Daniel Kiper <daniel.kiper@xxxxxxxxxx>
Tested-by: Daniel Kiper <daniel.kiper@xxxxxxxxxx>


Tested-by: Don Slutz <dslutz@xxxxxxxxxxx>

   -Don Slutz
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