Re: [Libguestfs] Debugging nested KVM guest (L2) booting with libguestfs/gdb
On Thu, Feb 13, 2014 at 12:08:37AM +0530, Kashyap Chamarthy wrote:
[. . .]
Try a couple more things
------------------------
- Run `qemu-sanity-check` in L1 -- Of course, this fails too.
- Invoke (from a different shell, as root) QEMU directly with gdb
debugging options -s -S with KVM on L1:
$ qemu-system-x86_64 -s -S -nographic -nodefconfig \
-nodefaults -machine accel=kvm -m 4000 \
-drive file=/home/tuser1/vmimages/fedora-20.qcow2,if=ide,format=qcow2,cache=none \
-serial stdio
So, using -serial mon:stdio like below, and using CTL+a to toggles
monitor and stdio (thanks to Amit Shah for the tip):
$ qemu-system-x86_64 -s -S -nographic -nodefconfig \
-nodefaults -enable-kvm -machine accel=kvm -m 4000 \
-drive file=/home/tuser1/vmimages/fedora-20.qcow2,format=qcow2,cache=none \
-device virtio-serial -serial mon:stdio
C-a h print this help
C-a x exit emulator
C-a s save disk data back to file (if -snapshot)
C-a t toggle console timestamps
C-a b send break (magic sysrq)
C-a c switch between console and monitor
C-a C-a sends C-a
QEMU 1.7.0 monitor - type 'help' for more information
(qemu)
(qemu) gdbserver
Duplicate ID 'gdb' for chardev
Could not open gdbserver on device 'tcp::1234'
(qemu)
Seems like out of the box, gdb debugging doesn't work? This[1] suggests
otherwise. The documentation here[2] seems to be sparse.
[1] http://wiki.qemu.org/download/qemu-doc.html#gdb_005fusage
[2] http://wiki.qemu.org/Documentation/Debugging
--
/kashyap