Re: [Qemu-devel] [RFC 1/1] Execute arbitrary QMP commands from command line

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* Eric Blake (eblake@redhat.com) wrote:
> On 01/29/2015 08:15 AM, Daniel P. Berrange wrote:
> 
> >> ./bin/qemu-system-x86_64 -nographic -nodefaults -qmp-command '{"execute": "migrate-set-capabilities", "arguments":{"capabilities":[{"capability":"xbzrle","state":true}]}}' -qmp-command '{"execute": "query-migrate-capabilities"}' -incoming tcp::444
> > 
> > I'm unclear how we'd easily deal with the response from commands
> > invoked this way, to get replies and/or errors. Also, it might
> > be the case that we need to conditionally run certain commands
> > depending on the result of earlier commands.
> > 
> > Wouldn't it make more sense to simply add a 'migrate_incoming' QMP
> > command, and stop using -incoming altogether, so we just have normal
> > QMP access ?
> 
> I agree - shoving more into the command line is the wrong direction;
> full power is better obtained by making the command line be the minimal
> needed to get into QMP control, and let QMP kick things off.
> 
> > 
> > eg,
> > 
> >     #  qemu-system-x86_64 ....device args...  -S
> >     (qmp) ....arbitrary QMP commands ..
> >     (qmp) {"execute":"migrate-incoming", "arguments": { "uri": "tcp::44" }}
> 
> The idea of a QMP command to trigger incoming migration looks
> reasonable.  We can probably use a qapi union for a nicer syntax,
> something like:
> 
> {"execute": "migrate-incoming", "arguments": {
>   "type": "tcp", "port": 44 } }
> vs.
> {"execute": "migrate-incoming", "arguments": {
>   "type": "fd", "fd": 0 } }
> vs.
> {"execute": "migrate-incoming", "arguments": {
>   "type": "exec", "command": [ "cat", "/path/to/file" ] } }
> 
> and so forth.

Compared to just taking a URI argument that Dan suggested, that's quite a
bit of rework to do the reworking of each transport which is pretty
trivial.

Dave
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK