[Crash-utility] Problem on getting kernel backtrace with a `virsh dump' dumped kvm dumpfile

Hi, I encountered a problem on getting backtrace with a `virsh dump' dumped kvm dumpfile, the bt command did not get kernel backtrace properly. guest kernel: 2.6.32 crash: 5.0.6 patched with qemu_ram_version_4.patch(attached) steps to get dumpfile: 1. virsh start vm 2. connect to vm, say by vnc 3. On guest, build and run the code: int main(void) { while (1); return 0; } 4. On host, run `virsh dump vm /mnt/data/kernel-2.6.32.dump3-userspace-endless-loop' Then run crash: crash /mnt/data/kernel/linux-2.6.32/System.map /mnt/data/kernel/linux-2.6.32/vmlinux /mnt/data/kernel-2.6.32.dump3-userspace-endless-loop got the result: crash 5.0.6 Copyright (C) 2002-2010 Red Hat, Inc. Copyright (C) 2004, 2005, 2006 IBM Corporation Copyright (C) 1999-2006 Hewlett-Packard Co Copyright (C) 2005, 2006 Fujitsu Limited Copyright (C) 2006, 2007 VA Linux Systems Japan K.K. Copyright (C) 2005 NEC Corporation Copyright (C) 1999, 2002, 2007 Silicon Graphics, Inc. Copyright (C) 1999, 2000, 2001, 2002 Mission Critical Linux, Inc. This program is free software, covered by the GNU General Public License, and you are welcome to change it and/or distribute copies of it under certain conditions. Enter "help copying" to see the conditions. This program has absolutely no warranty. Enter "help warranty" for details. GNU gdb (GDB) 7.0 Copyright (C) 2009 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html> This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. Type "show copying" and "show warranty" for details. This GDB was configured as "x86_64-unknown-linux-gnu"... SYSTEM MAP: /mnt/data/kernel/linux-2.6.32/System.map DEBUG KERNEL: /mnt/data/kernel/linux-2.6.32/vmlinux (2.6.32) DUMPFILE: /mnt/data/kernel-2.6.32.dump3-userspace-endless-loop CPUS: 1 DATE: Fri Aug 27 05:18:12 2010 UPTIME: 00:00:51 LOAD AVERAGE: 0.44, 0.11, 0.03 TASKS: 67 NODENAME: localhost.localdomain RELEASE: 2.6.32 VERSION: #2 SMP PREEMPT Wed Aug 25 15:26:48 CST 2010 MACHINE: x86_64 (2925 Mhz) MEMORY: 511.6 MB PANIC: "Oops: 0003 [#1] PREEMPT SMP " (check log for details) PID: 0 COMMAND: "swapper" TASK: ffffffff8158df70 [THREAD_INFO: ffffffff8154e000] CPU: 0 STATE: TASK_RUNNING WARNING: panic task not found crash> bt PID: 0 TASK: ffffffff8158df70 CPU: 0 COMMAND: "swapper" #0 [ffffffff8154fe28] schedule at ffffffff8138baa3 bt: invalid kernel virtual address: 41 type: "call byte" bt: invalid kernel virtual address: 44e6835ad type: "call byte" bt: load_memfile_offset: read: Success bt: read error: kernel virtual address: fffffffffffffffc type: "call byte" bt: invalid kernel virtual address: e7ab type: "call byte" bt: invalid kernel virtual address: e273 type: "call byte" bt: invalid kernel virtual address: 13a7b type: "call byte" bt: invalid kernel virtual address: 935cb type: "call byte" bt: load_memfile_offset: read: Success bt: read error: kernel virtual address: fffffffffffffffb type: "call byte" bt: invalid kernel virtual address: 935cb type: "call byte" #1 [ffffffff8154fef0] cpu_idle at ffffffff8100ad1e crash> Note the output of `bt' command. Without running that endless-loop code then `bt' got: crash> bt PID: 0 TASK: ffffffff8158df70 CPU: 0 COMMAND: "swapper" #0 [ffffffff8154fe28] schedule at ffffffff8138baa3 #1 [ffffffff8154fe48] apic_timer_interrupt at ffffffff8100c65e #2 [ffffffff8154fed0] need_resched at ffffffff810125a8 #3 [ffffffff8154fee0] default_idle at ffffffff81012e03 #4 [ffffffff8154fef0] cpu_idle at ffffffff8100acd6 crash> Any suggestions on how to solve the problem? Regards, Hu Tao