Difference between revisions of "Debugging Qemu"
From stoney cloud
| [unchecked revision] | [unchecked revision] |
| Line 1: | Line 1: | ||
Sometimes you must be able to analyse Qemu more in-depth than the log files allow to. | Sometimes you must be able to analyse Qemu more in-depth than the log files allow to. | ||
| − | For this, one can attach a | + | For this, one can attach a [https://www.gnu.org/software/gdb/ GDB] instance to a running Qemu process as long as it is started with the <code>-s</code> option. |
| − | To pass the required option from libvirt down to Qemu, one can use an additional namespace to pass along options to Qemu as | + | To pass the required option from libvirt down to Qemu, one can use an additional namespace to pass along options to Qemu as described [http://wiki.libvirt.org/page/QEMUSwitchToLibvirt#-s in the libvirt wiki]. |
Simply replace at the beginning of the XML (for example when editing using <code>virsh edit</code>): | Simply replace at the beginning of the XML (for example when editing using <code>virsh edit</code>): | ||
| Line 19: | Line 19: | ||
and then start the VM. | and then start the VM. | ||
| − | The GDB session | + | The [https://www.gnu.org/software/gdb/ GDB] session to attach to the process and continue to run it until you hit a bug: |
<pre> | <pre> | ||
Revision as of 15:14, 5 June 2014
Sometimes you must be able to analyse Qemu more in-depth than the log files allow to.
For this, one can attach a GDB instance to a running Qemu process as long as it is started with the -s option.
To pass the required option from libvirt down to Qemu, one can use an additional namespace to pass along options to Qemu as described in the libvirt wiki.
Simply replace at the beginning of the XML (for example when editing using virsh edit):
<domain type='kvm'>by
<domain type='kvm' xmlns:qemu='http://libvirt.org/schemas/domain/qemu/1.0'> <qemu:commandline><qemu:arg value='-s'/></qemu:commandline>
and then start the VM.
The GDB session to attach to the process and continue to run it until you hit a bug:
~ # gdb GNU gdb (Gentoo 7.6.2 p1) 7.6.2 Copyright (C) 2013 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-pc-linux-gnu". For bug reporting instructions, please see: <http://bugs.gentoo.org/>. (gdb) file /usr/bin/qemu-system- /usr/bin/qemu-system-: No such file or directory. (gdb) file /usr/bin/qemu-system-x86_64 Reading symbols from /usr/bin/qemu-system-x86_64...Reading symbols from /usr/lib64/debug/usr/bin/qemu-system-x86_64.debug...done. done. (gdb) target remote localhost:1234 Remote debugging using localhost:1234 Reading symbols from /lib64/ld-linux-x86-64.so.2...Reading symbols from /usr/lib64/debug/lib64/ld-2.17.so.debug...(no debugging symbols found)...done. (no debugging symbols found)...done. Loaded symbols for /lib64/ld-linux-x86-64.so.2 0xfffff8003d7ab25f in _start () from /lib64/ld-linux-x86-64.so.2 (gdb) c Continuing.
