On Thu, Mar 29, 2018 at 01:43:03PM +0200, Igor Mammedov wrote:
> On Wed, 28 Mar 2018 16:21:48 -0300
> Eduardo Habkost <ehabk...@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 <imamm...@redhat.com> wrote:
> > >
> > > > On Fri, 23 Mar 2018 18:25:08 -0300
> > > > Eduardo Habkost <ehabk...@redhat.com> wrote:
> > > >
> > > > > On Mon, Mar 12, 2018 at 02:11:09PM +0100, Igor Mammedov wrote:
> > > > [...]
> > > [...]
> > > > > > @@ -1886,6 +1895,13 @@ static bool main_loop_should_exit(void)
> > > > > > RunState r;
> > > > > > ShutdownCause request;
> > > > > >
> > > > > > + if (preconfig_exit_requested) {
> > > > > > + if (runstate_check(RUN_STATE_PRECONFIG)) {
> > > > >
> > > > > Is it possible to have preconfig_exit_request set outside of
> > > > > RUN_STATE_PRECONFIG? When and why?
> > > > preconfig_exit_requested is initialized with TRUE and
> > > > in combo with '-inmigrate' we need this runstate check.
> > > > it's the same as it was with
> > > > { RUN_STATE_PRELAUNCH, RUN_STATE_INMIGRATE },
> > > > which I probably should remove (I need to check it though)
> > > [...]
> > >
> > > > > > @@ -4594,6 +4623,10 @@ int main(int argc, char **argv, char **envp)
> > > > > > }
> > > > > > parse_numa_opts(current_machine);
> > > > > >
> > > > > > + /* do monitor/qmp handling at preconfig state if requested */
> > > > > > + main_loop();
> > > > >
> > > > > Wouldn't it be simpler to do "if (!preconfig) { main_loop(); }"
> > > > > instead of entering main_loop() just to exit immediately?
> > > > The thought didn't cross my mind, it might work and more readable
> > > > as one doesn't have to jump into main_loop() to find out that
> > > > it would exit immediately.
> > > > I'll try to it on respin.
> > > Well doing as suggested end ups more messy:
> > >
> > > @@static bool main_loop_should_exit(void)
> > > ...
> > > if (preconfig_exit_requested) {
> > > runstate_set(RUN_STATE_PRELAUNCH);
> > >
> > > return true;
> > > }
> > >
> > > @@main
> > > /* do monitor/qmp handling at preconfig state if requested */
> > > if (!preconfig_exit_requested) {
> > > main_loop();
> > > } else if (runstate_check(RUN_STATE_PRECONFIG)) {
> > > runstate_set(RUN_STATE_PRELAUNCH);
> > > }
> >
> > 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
That explains a lot, thanks.
>
> Another variant 2, in case we switch to RUN_STATE_PRECONFIG only on -preconfig
> transitions would be
> RUN_STATE_PRELAUNCH -> RUN_STATE_PRECONFIG
> (allow switch from initial to -preconfig)
>
> RUN_STATE_PRECONFIG -> RUN_STATE_PRELAUNCH
>
> while the last is valid transition, the 1st one isn't really
> valid because of (beside of switching from initial state) it
> allows bouncing back to RUN_STATE_PRECONFIG later.
>
> If we consider only state machine transitions, I think it's
> cleaner to start with variant 1 with the same
> -inmigrate hack we already have (which potentially could
> be fixed later), than allowing arbitrary bouncing to
> RUN_STATE_PRECONFIG at later stage.
>
> With this approach all processing before machine_init()
> would run at RUN_STATE_PRECONFIG and then we would switch
> to RUN_STATE_PRELAUNCH. Even though it is far reaching
> goal but at least that's where we should be moving to
> have sane initialization flow in vl.c
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).
>
> > > preconfig_exit_requested = false;
> > > ...
> > >
> > > I'd prefer original v4 approach, where only main_loop_should_exit()
> > > has to deal with state transitions and book-keeping.
> >
> > If the above is unavoidable, I agree. But I still don't
> > understand we have to enter PRECONFIG state if the user didn't
> > specify -preconfig.
> >
>
--
Eduardo
