Re: [Qemu-devel] [Qemu-block] Supplying QCOW2 as 'file' driver to `blockdev-add` results in a QEMU crash

[Kashyap Chamarthy]

On Wed, Jun 15, 2016 at 11:58:31AM +0200, Kashyap Chamarthy wrote:
> Seems like supplying "qcow2" file BlockdevDriver option to QMP
> `blockdev-add` results in a SIGSEGV:
> 
>       [...]
>     Thread 1 "qemu-system-x86" received signal SIGSEGV, Segmentation fault.
>     0x0000555555a0121f in visit_type_BlockdevRef ()
>       [...]
> 

[...]
 
> Then, invoke the 'blockdev-add' QMP command with these arguments and options:
> 
>     $ socat UNIX:/export/qmp-sock 
> READLINE,history=$HOME/.qmp_history,prompt='QMP> '
>     {"QMP": {"version": {"qemu": {"micro": 0, "minor": 6, "major": 2}, 
> "package": " (qemu-2.6.0-3.fc24)"}, "capabilities": []}}
>     QMP> {"execute":"qmp_capabilities"}
>     {"return": {}}
>     
>     QMP> { "execute": "blockdev-add",
>          "arguments": { "options" : { "driver": "qcow2", 
>                                      "id": "drive-ide1-0-0",
>                                      "file": { "driver": "qcow2",
>                                                "filename": "backup1.qcow2" } 
> } } }
> 

[...]

Related SIGSEGV case:

(1) driver: raw, file: driver: raw

    QMP> { "execute": "blockdev-add",
         "arguments": { "options" : { "driver": "raw", 
                                     "id": "drive-ide1-0-0",
                                     "file": { "driver": "raw",
                                               "filename": "/tmp/test1.raw" } } 
} }


And the below are the *good* cases, where the block device is added
successfully:

(2) driver: qcow2, file: driver: file

    $ qemu-img create -f qcow2 /tmp/test2.qcow2 512M

    QMP> { "execute": "blockdev-add",
         "arguments": { "options" : { "driver": "qcow2", 
                                     "id": "drive-ide2-0-0",
                                     "file": { "driver": "file",
                                               "filename": "/tmp/test2.qcow2" } 
} } }
    {"return": {}}


(3) driver: raw, file: driver: file

    $ qemu-img create -f raw /tmp/test3.raw 512M

    QMP> { "execute": "blockdev-add",
         "arguments": { "options" : { "driver": "raw", 
                                     "id": "drive-ide3-0-0",
                                     "file": { "driver": "file",
                                               "filename": "/tmp/test3.raw" } } 
} }
    {"return": {}}

-- 
/kashyap