Re: [Qemu-devel] [PATCH v4 3/9] cli: add -preconfig option

[Eduardo Habkost <ehabkost@redhat.com>]

On Tue, Apr 03, 2018 at 04:32:53PM +0200, Igor Mammedov wrote:
> On Thu, 29 Mar 2018 13:24:09 -0300
> Eduardo Habkost <ehabkost@redhat.com> wrote:
> 
> > On Thu, Mar 29, 2018 at 01:43:03PM +0200, Igor Mammedov wrote:
> > > On Wed, 28 Mar 2018 16:21:48 -0300
> > > Eduardo Habkost <ehabkost@redhat.com> wrote:
> > >   
> > > > On Wed, Mar 28, 2018 at 01:48:35PM +0200, Igor Mammedov wrote:  
> > > > > On Tue, 27 Mar 2018 17:05:41 +0200
> > > > > Igor Mammedov <imammedo@redhat.com> wrote:
> > > > >     
> > > > > > On Fri, 23 Mar 2018 18:25:08 -0300
> > > > > > Eduardo Habkost <ehabkost@redhat.com> wrote:
> [...]
> > > > This doesn't make sense to me.  Why would we enter
> > > > RUN_STATE_PRECONFIG state if -preconfig is not used at all?  
> > > because of RUN_STATE_PRECONFIG becomes new initial state of
> > > our state machine where we start of (used to be RUN_STATE_PRELAUNCH)  
> > 
> > Oh, I missed that part.
> > 
> > > Lets call it variant 1:
> > > 
> > > with this we have 2 possible transitions:
> > >  RUN_STATE_PRECONFIG -> RUN_STATE_PRELAUNCH (machine_init)
> > > 
> > > and
> > > 
> > >  RUN_STATE_PRECONFIG -> RUN_STATE_INMIGRATE
> > >    ugly but it was the same with RUN_STATE_PRELAUNCH initial transition  
> [...]
> > 
> > Thanks, now variant 1 makes more sense to me.  But I really miss
> > here are very clear and explicit descriptions of what each state
> > really mean, and what are the differences between them.
> > 
> > It looks like the existing description for `prelaunch` isn't
> > accurate:
> > 
> > # @prelaunch: QEMU was started with -S and guest has not started
> > 
> > This is false, as QEMU can be in `prelaunch` state even if -S is
> > not used.
> > 
> > 
> > Also, this is the description you proposed for `preconfig`:
> > 
> > # @preconfig: QEMU is paused before board specific init callback is executed.
> > #             The state is reachable only if -preconfig CLI option is used.
> > #             (Since 2.12)
> > 
> > This seems wrong as well: the `prelaunch` state is reachable even
> > if `-preconfig` isn't used in the command-line (because it is the
> > initial state).
> I'm not sure we should describe transitions/initial state here
> (it's not the case now).
> 
> I think descriptions 'almost' match 'end' result of what QMP client
> cloud see and the initial state is not something that QMP user could
> observe.

That's my impression as well: `prelaunch` should be visible
externally only if `-S` was used, and `preconfig` should be
visible externally only if `-preconfig` was used.

However, I miss documentation on what are the
expectations/requirements internally.  e.g. there's no
explanation why a reset request moves QEMU to
RUN_STATE_PRELAUNCH.  Ideally, each line in
runstate_transition_def would have a clear explanation for
when/why each transition happens.

But this isn't a requirement for the new feature you are
implementing, anyway.

-- 
Eduardo