Re: [Qemu-devel] [PATCH v4 5/9] qapi: introduce new cmd option "allowed-in-preconfig"

[Eduardo Habkost <ehabkost@redhat.com>]

On Wed, Mar 28, 2018 at 02:29:57PM +0200, Igor Mammedov wrote:
> On Fri, 23 Mar 2018 18:28:37 -0300
> Eduardo Habkost <ehabkost@redhat.com> wrote:
> 
> > On Mon, Mar 12, 2018 at 02:11:11PM +0100, Igor Mammedov wrote:
> > > New option will be used to allow commands, which are prepared/need
> > > to run run in preconfig state. Other commands that should be able
> > > to run in preconfig state, should be ammeded to not expect machine
> > > in initialized state or deal with it.
> > > 
> > > For compatibility reasons, commands, that don't use new flag
> > > 'allowed-in-preconfig' explicitly, are not permited to run in
> > > preconfig state but allowed in all other states like they used
> > > to be.
> > > 
> > > Within this patch allow following commands in preconfig state:
> > >    qmp_capabilities
> > >    query-qmp-schema
> > >    query-commands
> > >    query-status
> > >    cont
> > > to allow qmp connection, basic introspection and moving to the next
> > > state.
> > > 
> > > PS:
> > > set-numa-node and query-hotpluggable-cpus will be enabled later in
> > > a separate patch.
> > > 
> > > Signed-off-by: Igor Mammedov <imammedo@redhat.com>  
> > 
> > I didn't review the code yet, but:
> > 
> > Shouldn't this be applied before patch 3/9, for bisectability?
> > Otherwise it will be very easy to crash QEMU after applying patch
> > 3/9.
> no, it isn't going to work.
> This patch depends on RUN_STATE_PRECONFIG that is introduced in 3/9.
> 
> It could be fine to merge into 3/9 during merge, but then history
> wise it would be difficult to read it later with 2 big and mostly
> separate changes within one patch.

Yeah, I don't think squashing would be the right answer.

> 
> Considering -preconfig if off by default it shouldn't affect
> bisectability in general so I'd keep current patch order.

Well, it would affect bisectability if debugging a crash that
happens using -preconfig.

The only hunk in this patch that really depends on patch 3/9
seems to be:

  @@ -92,6 +93,13 @@ static QObject *do_qmp_dispatch(QmpCommandList *cmds, QObject *request,
           return NULL;
       }
  
  +    if (runstate_check(RUN_STATE_PRECONFIG) &&
  +        !(cmd->options & QCO_ALLOWED_IN_PRECONFIG)) {
  +        error_setg(errp, "The command '%s' isn't permitted in '%s' state",
  +                   cmd->name, RunState_str(RUN_STATE_PRECONFIG));
  +        return NULL;
  +    }
  +
       if (!qdict_haskey(dict, "arguments")) {
           args = qdict_new();
       } else {
  

What about moving it to patch 3/9?


Or, an alternative is to move the following hunk from patch 3/9 to this patch:

  diff --git a/qapi/run-state.json b/qapi/run-state.json
  index 1c9fff3aef..ce846a570e 100644
  --- a/qapi/run-state.json
  +++ b/qapi/run-state.json
  @@ -49,12 +49,15 @@
   # @colo: guest is paused to save/restore VM state under colo checkpoint,
   #        VM can not get into this state unless colo capability is enabled
   #        for migration. (since 2.8)
  +# @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)
   ##
   { 'enum': 'RunState',
     'data': [ 'debug', 'inmigrate', 'internal-error', 'io-error', 'paused',
               'postmigrate', 'prelaunch', 'finish-migrate', 'restore-vm',
               'running', 'save-vm', 'shutdown', 'suspended', 'watchdog',
  -            'guest-panicked', 'colo' ] }
  +            'guest-panicked', 'colo', 'preconfig' ] }
  
   ##
   # @StatusInfo:

Which could be an interesting idea, because the QAPI schema
changes would be all grouped inside a single patch, and then
followed by the actual implementation of the -preconfig option.

-- 
Eduardo