Re: [Qemu-devel] [PATCH 8/8] qom: Make CPU a child of DeviceState

[Igor Mammedov <imammedo@redhat.com>]

On Wed, 02 Jan 2013 16:08:42 +0100
Andreas Färber <afaerber@suse.de> wrote:

> Am 05.12.2012 17:49, schrieb Eduardo Habkost:
> > This finally makes the CPU class a child of DeviceState, allowing us to
> > start using DeviceState properties on CPU subclasses.
> 
> To avoid confusion with child<> properties and DeviceState vs.
> DeviceClass I have reworded this to "subclass of Device" in my
> qom-cpu-dev queue.
> 
> > 
> > It has no_user=1, as creating CPUs using -device doesn't work yet.
> > 
> 
> > (based on a previous patch from Igor Mammedov)
> 
> Can this comment be turned into or amended by the usual Signed-off-by?
Signed-off-by should be ok.

> 
> > 
> > Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
> > ---
> > Changes v1 (imammedo) -> v2 (ehabkost):
> >  - Change CPU type declaration to hae TYPE_DEVICE as parent
> > 
> > Changes v2 -> v3 (ehabkost):
> >  - Set no_user=1 on the CPU class
> > ---
> >  include/qemu/cpu.h | 6 +++---
> >  qom/cpu.c          | 5 ++++-
> >  2 files changed, 7 insertions(+), 4 deletions(-)
> > 
> > diff --git a/include/qemu/cpu.h b/include/qemu/cpu.h
> > index 61b7698..bc004fd 100644
> > --- a/include/qemu/cpu.h
> > +++ b/include/qemu/cpu.h
> > @@ -20,7 +20,7 @@
> >  #ifndef QEMU_CPU_H
> >  #define QEMU_CPU_H
> >  
> > -#include "qemu/object.h"
> > +#include "hw/qdev-core.h"
> >  #include "qemu-thread.h"
> >  
> >  /**
> [...]
> > diff --git a/qom/cpu.c b/qom/cpu.c
> > index 5b36046..d301f72 100644
> > --- a/qom/cpu.c
> > +++ b/qom/cpu.c
> > @@ -20,6 +20,7 @@
> >  
> >  #include "qemu/cpu.h"
> >  #include "qemu-common.h"
> > +#include "hw/qdev-core.h"
> 
> Already included via qom/cpu.h (formerly qemu/cpu.h) above, dropping.
> 
> >  
> >  void cpu_reset(CPUState *cpu)
> >  {
> > @@ -36,14 +37,16 @@ static void cpu_common_reset(CPUState *cpu)
> >  
> >  static void cpu_class_init(ObjectClass *klass, void *data)
> >  {
> > +    DeviceClass *dc = DEVICE_CLASS(klass);
> >      CPUClass *k = CPU_CLASS(klass);
> >  
> >      k->reset = cpu_common_reset;
> > +    dc->no_user = 1;
> >  }
> 
> I wonder if we should add a comment that we are intentionally not
> hooking up dc->reset (yet)?
not relevant to this patch, could be separate patch though.

> 
> >  
> >  static TypeInfo cpu_type_info = {
> 
> Would like to add the missing const while touching this.
> 
> >      .name = TYPE_CPU,
> > -    .parent = TYPE_OBJECT,
> > +    .parent = TYPE_DEVICE,
> >      .instance_size = sizeof(CPUState),
> >      .abstract = true,
> >      .class_size = sizeof(CPUClass),
> 
> My testing so far confirms that the combination of object_new() without
> qdev_init[_nofail]() is working fine.
+1, I tested this combo for (x86)-(softmmu|linux-user) targets, no issues were
found so far.

> 
> Using qdev_create() in the current state of stubs would lead to a silly
> if-bus-is-NULL-set-it-to-NULL sequence on top of object_new(). I do not
> expect qdev_create() to grow in functionality, so continuing to use
> object_new() should be okay - SoCs like my Tegra model may want to use
> object_initialize() so we cannot prescribe using qdev_create() anyway.
> 
> qdev_init_nofail() would call the qdev initfn (to be replaced by
> realizefn, not used for CPU in this patch), then if no parent add it to
> /machine/unassigned, register VMSD if not NULL, update the internal
> state (blocking static property changes) and if hotplugged reset (unused
> due to dc->no_user and lack of dc->reset). The /machine/unassigned part
> may be interesting, e.g., for APIC modelling (so that we can model the
> former ptr property / now pointer-setting as a link<> property).
> 
> With these considerations I am leaning towards accepting this patch if
> nobody objects, so that we can move on to the next refactorings...
+1

> 
> Regards,
> Andreas
>