Re: [Qemu-devel] [PATCH 6/6] arm: drop intermadiate cpu_model -> cpu type parsing and use cpu type directly

[Eduardo Habkost <ehabkost@redhat.com>]

On Tue, Sep 05, 2017 at 02:47:52PM -0700, Alistair Francis wrote:
> On Tue, Sep 5, 2017 at 2:31 PM, Eduardo Habkost <ehabkost@redhat.com> wrote:
[...]
> >> diff --git a/hw/arm/stm32f205_soc.c b/hw/arm/stm32f205_soc.c
> >> index f61e735..1cd6374 100644
> >> --- a/hw/arm/stm32f205_soc.c
> >> +++ b/hw/arm/stm32f205_soc.c
> >> @@ -112,7 +112,7 @@ static void stm32f205_soc_realize(DeviceState *dev_soc, Error **errp)
> >>
> >>      armv7m = DEVICE(&s->armv7m);
> >>      qdev_prop_set_uint32(armv7m, "num-irq", 96);
> >> -    qdev_prop_set_string(armv7m, "cpu-model", s->cpu_model);
> >> +    qdev_prop_set_string(armv7m, "cpu-type", s->cpu_type);
> >>      object_property_set_link(OBJECT(&s->armv7m), OBJECT(get_system_memory()),
> >>                                       "memory", &error_abort);
> >>      object_property_set_bool(OBJECT(&s->armv7m), true, "realized", &err);
> >> @@ -200,7 +200,7 @@ static void stm32f205_soc_realize(DeviceState *dev_soc, Error **errp)
> >>  }
> >>
> >>  static Property stm32f205_soc_properties[] = {
> >> -    DEFINE_PROP_STRING("cpu-model", STM32F205State, cpu_model),
> >> +    DEFINE_PROP_STRING("cpu-type", STM32F205State, cpu_type),
> >
> > Same as armv7m: are we 100% sure users are not setting this
> > manually?
> 
> In an embedded board like this it really doesn't make sense to let the
> user overwrite the CPU. The SoC will take it as an option, but the
> board (which creates the SoC) just blindly always uses the same CPU.
> That feature is more for QOMificatoion then any real reason though.
> 

I'm not talking about -cpu (no user-visible change in the
handling of -cpu should result from this patch), but about
possible cases where the user set the "cpu-model" property using
another mechanism, like -global.  Probably it's impossible for an
user to override the property successfully, but I would like to
be sure.


> In saying that I think a warning if the user tries to set the CPU
> would make sense. I know that this issues comes up in other ARM boards
> (Zynq-7000 has the same issue as well) so maybe a machine property
> saying that the board doesn't accept custom CPUs would be a good idea.

Yeah, there are multiple cases in this patch where boards are
validating the CPU model, but not all boards do that.  A generic
MachineClass::valid_cpu_types[] field would be useful.

> 
> Overall I think this patch is moving in the right direction though and
> this CPU option being ignored existed before this series.

I agree this is going on the right direction.  However, I don't
see any board that ignore the CPU option: all of them seem to use
cpu_model when creating the CPUs, already.

-- 
Eduardo