Re: [Qemu-devel] QMP: RFC: I/O error info & query-stop-reason

[Luiz Capitulino <lcapitulino@redhat.com>]

On Fri, 3 Jun 2011 14:39:41 +0100
"Daniel P. Berrange" <berrange@redhat.com> wrote:

> On Fri, Jun 03, 2011 at 08:26:56AM -0500, Anthony Liguori wrote:
> > On 06/03/2011 07:57 AM, Daniel P. Berrange wrote:
> > >On Fri, Jun 03, 2011 at 07:43:24AM -0500, Anthony Liguori wrote:
> > >>On 06/03/2011 04:26 AM, Daniel P. Berrange wrote:
> > >>errors stop a guest) instead of trying to model an internal QEMU
> > >>concept (vm_stop()).
> > >>
> > >>If you have other user visible concepts that you want to know about,
> > >>please share the use-cases and we can think about how to model it
> > >>such that it's not exposing internal QEMU details.
> > >
> > >None of the requested info is exposing internal QEMU impl details
> > >with one exception. The reasons are either administrative commands,
> > >host OS failures, guest OS failures, or the exception, KVM internal
> > >emulation failure.
> > >
> > >The core problem is that an app connects to QEMU, finds it is paused,
> > >and wants to decide what action to take. If the guest is paused due
> > >to a previous admin 'stop' command,
> > 
> > Let's be very clear here.  QEMU does not provide a way to figure out
> > what the previous QMP user did.  That is not a use case we support
> > today and it's not one we can support by just adding a reason to
> > stop.  It's far more complicated than just that.
> > 
> > >it will allow resuming. If it is
> > >paused due to guest OS poweroff,
> > 
> > This is legitimate but only occurs if you use -no-shutdown.  So
> > having a query-state have a "powered-off" flag would be a Good
> > Thing.
> > 
> > >it might decide to issue a 'system_reset'
> > >command and then 'resume'. If it is paused due to watchdog,
> > 
> > I think what we're getting at is the need for an enumeration.  So
> > let's introduce one.  Here's what I propose:
> > 
> > SQMP
> > query-status
> > ------------
> > 
> > Return a json-object with the following information:
> > 
> > - "running": true if the VM is running, or false if it is paused (json-bool)
> > - "singlestep": true if the VM is in single step mode,
> >                 false otherwise (json-bool)
> > - "status": one of the following values (json-string) (optional)
> >       "prelaunch" - QEMU was started with -S and guest has not started
> >       "running" - guest is actively running
> >       "singlestep" - guest is running in single step mode
> >       "paused" - guest has been paused via the 'stop' command
> >       "postmigrate" - guest is paused following a successful 'migrate'
> >       "shutdown" - guest is shut down (and -no-shutdown is in use)
> >       "io-error" - the last IOP has failed and the device is
> > configured to pause on I/O errors
> >       "watchdog-error" - the watchdog action is configured to pause
> > and has been triggered
> 
> Perhaps I didn't communicate well, but this pretty much matches
> what I was trying to ask for in my previous message, so gets
> my vote!

Mine too, I like it. Expect patches next week :)

My only comment is that, in case this an improved version of
query-status we could have a new command (like query-statys2 or
query-vm-status).