Re: [Qemu-devel] qemu-kvm guest which won't 'cont' (emulation failure?)

[Chris Webb <chris@arachsys.com>]

Kevin Wolf <kwolf@redhat.com> writes:

> Good point... The only other thing that I can think of would be
> attaching gdb and setting a breakpoint in vm_stop() or something.

Perfect, that seems to identified what's going on very nicely:

(gdb) break vm_stop
Breakpoint 1 at 0x407d10: file /home/root/packages/qemu-kvm/src-UMBurO/cpus.c, line 318.
(gdb) fg
Continuing.

Breakpoint 1, vm_stop (reason=0)
    at /home/root/packages/qemu-kvm/src-UMBurO/cpus.c:318
318     /home/root/packages/qemu-kvm/src-UMBurO/cpus.c: No such file or directory.
        in /home/root/packages/qemu-kvm/src-UMBurO/cpus.c
(gdb) bt
#0  vm_stop (reason=0) at /home/root/packages/qemu-kvm/src-UMBurO/cpus.c:318
#1  0x000000000058585f in ide_handle_rw_error (s=0x20330d8, error=28, op=8)
    at /home/root/packages/qemu-kvm/src-UMBurO/hw/ide/core.c:468
#2  0x0000000000588376 in ide_dma_cb (opaque=0x20330d8, 
    ret=<value optimized out>)
    at /home/root/packages/qemu-kvm/src-UMBurO/hw/ide/core.c:494
#3  0x0000000000590092 in dma_bdrv_cb (opaque=0x2043a10, ret=-28)
    at /home/root/packages/qemu-kvm/src-UMBurO/dma-helpers.c:94
#4  0x000000000044d64a in qcow2_aio_write_cb (opaque=0x2034900, ret=-28)
    at block/qcow2.c:714
#5  0x000000000043df6d in posix_aio_process_queue (
    opaque=<value optimized out>) at posix-aio-compat.c:462
#6  0x000000000043e07d in posix_aio_read (opaque=0x17c8110)
    at posix-aio-compat.c:503
#7  0x0000000000415fca in main_loop_wait (nonblocking=<value optimized out>)
    at /home/root/packages/qemu-kvm/src-UMBurO/vl.c:1383
#8  0x000000000042ca37 in kvm_main_loop ()
    at /home/root/packages/qemu-kvm/src-UMBurO/qemu-kvm.c:1589
#9  0x00000000004170a3 in main (argc=32, argv=<value optimized out>, 
    envp=<value optimized out>)
    at /home/root/packages/qemu-kvm/src-UMBurO/vl.c:1429

I see what's happened here: we're not explicitly setting format=raw when we
start that guest and someone's uploaded a qcow2 image directly to a block
device. Ouch. Sorry for the noise!

Best wishes,

Chris.