Re: [Qemu-devel] [PATCH 0/3] QEMU logging improvements

[Kashyap Chamarthy <kchamart@redhat.com>]

On Thu, Oct 15, 2015 at 06:18:31PM +0300, Pavel Butsykin wrote:
> 
> On 15.10.2015 17:49, Kashyap Chamarthy wrote:
> >On Thu, Oct 15, 2015 at 10:30:21AM +0300, Denis V. Lunev wrote:
> >>The following is done:
> >>- QMP/HMP events are now logged
> >
> >I applied this patch series locally, and tried to test it the below way:
> >
> >Launch a minimal QEMU instance:
> >
> >   $ /home/kashyapc/build/build-qemu-upstream/x86_64-softmmu/qemu-system-x86_64 \
> >    -nographic                      \
> >    -nodefconfig                    \
> >    -nodefaults                     \
> >    -m 2048                         \
> >    -cpu SandyBridge                \
> >    -device virtio-scsi-pci,id=scsi \
> >    -device virtio-serial-pci       \
> >    -drive file=./cirros.qcow2,if=virtio,cache=writeback \
> >    -serial stdio \
> >    -D ./output-of-qemu.txt \
> >    -qmp unix:./qmp-sock,server
> >
> >And, issued QMP commands via `qmp-shell`:
> >
> >   $ ./qmp-shell /export/qmp-sock
> >   Welcome to the QMP low-level shell!
> >   Connected to QEMU 2.4.50
> >   (QEMU)
> >   (QEMU) query-status
> >   {"return": {"status": "running", "singlestep": false, "running": true}}
> >   (QEMU)
> >   (QEMU) blockdev-snapshot-internal-sync device=virtio0 name=snapshot1
> >   {"return": {}}

[. . .]

> You forgot to specify the mask: -d cmd,time
> 
> qemu$ qemu-system-x86_64 -h|grep log
> ...
> -d item1,...    enable logging of specified items (use '-d help' for a list
> of log items)

Ah, my bad.  Thanks for pointing it out, Pavel.

> -D logfile      output log to logfile (default stderr)
> 
> So it should work:
>     $
> /home/kashyapc/build/build-qemu-upstream/x86_64-softmmu/qemu-system-x86_64 \
>      -nographic                      \
>      -nodefconfig                    \
>      -nodefaults                     \
>      -m 2048                         \
>      -cpu SandyBridge                \
>      -device virtio-scsi-pci,id=scsi \
>      -device virtio-serial-pci       \
>      -drive file=./cirros.qcow2,if=virtio,cache=writeback \
>      -serial stdio \
>      -D ./output-of-qemu.txt \
>      -d cmd,time \
>      -qmp unix:./qmp-sock,server
> 

Yep, '-d cmd,time' perfectly logs the QMP requests/response, on stdio,
when I invoke QMP commands from a different shell:


    $ ./qemu-system-x86_64 \
    [. . .]
    2015-10-15 17:38:58.474 qmp request:
    {
        "execute": "blockdev-snapshot-internal-sync",
        "arguments": {
            "name": "snapshot2",
            "device": "virtio0"
        }
    }
    2015-10-15 17:38:58.488 qmp response:
    {
        "return": {
        }
    }
    2015-10-15 17:39:25.743 qmp request:
    {
        "execute": "quit",
        "arguments": {
        }
    }
    2015-10-15 17:39:25.743 qmp response:
    {
        "return": {
        }
    }
    2015-10-15 17:39:25.744 qmp event:
    {
        "timestamp": {
            "seconds": 1444923565,
            "microseconds": 744211
        },
        "event": "SHUTDOWN"
    }


    * * *

Also, Stefan Hajnoczi pointed out on IRC that: "-D is mainly a TCG
thing.  There are plenty of fprintf(stderr) calls in QEMU".  So, the
stderr might not be affected by it.


-- 
/kashyap