Re: [Qemu-devel] feature idea: allow user to run custom scripts

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

* Markus Armbruster (armbru@redhat.com) wrote:
> "Dr. David Alan Gilbert" <dgilbert@redhat.com> writes:
> 
> > * Markus Armbruster (armbru@redhat.com) wrote:
> >> "Dr. David Alan Gilbert" <dgilbert@redhat.com> writes:
> >> 
> >> > * Peter Maydell (peter.maydell@linaro.org) wrote:
> >> >> On 29 September 2015 at 14:11, Dr. David Alan Gilbert
> >> >> <dgilbert@redhat.com> wrote:
> >> >> > * Peter Maydell (peter.maydell@linaro.org) wrote:
> >> >> >> On 28 September 2015 at 20:43, Programmingkid
> >> >> >> <programmingkidx@gmail.com> wrote:
> >> >> >> >
> >> >> >> > On Sep 28, 2015, at 3:29 AM, Markus Armbruster wrote:
> >> >> >> >> You didn't mention you're talking about a *GUI* feature.
> >> >> >> >
> >> >> >> > I'm thinking it would be easier to send in the patch rather
> >> >> >> > than talk about
> >> >> >> > what this feature could be.
> >> >> >>
> >> >> >> I think Markus and I are trying to save you that effort by
> >> >> >> pointing out that this is a VM management layer feature,
> >> >> >> not a core QEMU feature.
> >> >> >
> >> >> > OK, so I'm going to agree with Programmingkid here.
> >> >> > I think this would be a useful feature to have in QEMU; I've
> >> >> > got gratuitous hacks in some of my test scripts that work
> >> >> > around it not being there.
> >> >> >
> >> >> > I think there are two possible things, both of which seem fairly
> >> >> > easy:
> >> >> >   1) Add a -chardev from file that works in this case
> >> >> >      (I don't think the current chardev file works does it?)
> >> 
> >> In general, character devices provide a bidirectional pipe, but -chardev
> >> file is write-only.  I think you want -chardev pipe.  I don't use it
> >> myself, because as socat user, I don't have to learn lesser tools :)
> >> 
> >> Here's how I use it.  Set up a local socket (any convenient
> >> bidirectional pipe would do, actually).
> >> 
> >> Example: QMP
> >> 
> >>     # Configuration file for -readconfig
> >>     [chardev "qmp"]
> >>       backend = "socket"
> >>       path = "sock-qmp"
> >>       server = "on"
> >>       wait = "off"
> >> 
> >>     [mon "qmp"]
> >>       mode = "control"
> >>       chardev = "qmp"
> >> 
> >> Example: HMP
> >> 
> >>     [chardev "hmp"]
> >>       backend = "socket"
> >>       path = "sock-hmp"
> >>       server = "on"
> >>       wait = "off"
> >> 
> >>     [mon "hmp"]
> >>       mode = "readline"
> >>       chardev = "hmp"
> >> 
> >> Then do stuff with it.
> >> 
> >> Example: interactive QMP
> >> 
> >>     $ socat UNIX:sock-qmp READLINE,history=$HOME/.qmp_history,prompt='QMP> '
> >> 
> >> Example: interactive HMP
> >> 
> >>     $ socat UNIX:sock-hmp READLINE,history=$HOME/.hmp_history
> >> 
> >> Arguably superior to our built-in not-quite readline monitor.
> >> 
> >> Example: send QMP input from a file, capture its output in a file
> >> 
> >>     $ socat UNIX:sock-qmp STDIO <input >output
> >
> > Yes, this example is exactly why I want something less painful.
> > A -chardev file that allowed read/write would be ideal, to be able to read
> > a series of commands at startup.
> 
> Have you tried -chardev pipe?  As I said, I don't use it myself, because
> my "painful" setup is more flexible, and not painful at all once set up.

Yes, I do use -chardev pipe in some of my scripts, and yes it's simpler
than the socket setup, but it's still a lot more complex than just stuffing
a list of commands in.

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