Re: [PATCH v4 4/8] ppc/e500: Use start-powered-off CPUState property

[Igor Mammedov <imammedo@redhat.com>]

On Tue, 18 Aug 2020 00:33:19 -0300
Thiago Jung Bauermann <bauerman@linux.ibm.com> wrote:

[...]

> Also change creation of CPU object from cpu_create() to object_new() and
> qdev_realize() because cpu_create() realizes the CPU and it's not possible
> to set a property after the object is realized.

cpu_create was introduced to remove code duplication in simple cases where
we do not need to set properties on created cpu.

returning back to manual object_new + realize() is fine if it 's only
small set of of boards. If it's tree-wide change then that would bring
back all code duplication that cpu_create() got rid of.

An alternative way is to use 'hotplug' callbacks to let board set
additional properties before cpu's realize is called.

example:
  hw/ppc/spapr.c:
   spapr_machine_class_init()
     mc->get_hotplug_handler = spapr_get_hotplug_handler;                         
     hc->pre_plug = spapr_machine_device_pre_plug; 
   ...
   static const TypeInfo spapr_machine_info = {
   ...
        { TYPE_HOTPLUG_HANDLER },

that might work in generic case if it is put into generic machine code,
and existing users of mc->get_hotplug_handler/hc->pre_plug were taken care of.
In which case board would only need to set MachineClass:cpu-start-powered-of
to gate property setting.

 
> Signed-off-by: Thiago Jung Bauermann <bauerman@linux.ibm.com>
> ---
>  hw/ppc/e500.c | 19 +++++++++++++++----
>  1 file changed, 15 insertions(+), 4 deletions(-)
> 
> diff --git a/hw/ppc/e500.c b/hw/ppc/e500.c
> index ab9884e315..0077aca74d 100644
> --- a/hw/ppc/e500.c
> +++ b/hw/ppc/e500.c
> @@ -704,9 +704,6 @@ static void ppce500_cpu_reset_sec(void *opaque)
>  
>      cpu_reset(cs);
>  
> -    /* Secondary CPU starts in halted state for now. Needs to change when
> -       implementing non-kernel boot. */
> -    cs->halted = 1;
>      cs->exception_index = EXCP_HLT;
>  }
>  
> @@ -864,8 +861,9 @@ void ppce500_init(MachineState *machine)
>          PowerPCCPU *cpu;
>          CPUState *cs;
>          qemu_irq *input;
> +        Error *err = NULL;
>  
> -        cpu = POWERPC_CPU(cpu_create(machine->cpu_type));
> +        cpu = POWERPC_CPU(object_new(machine->cpu_type));
>          env = &cpu->env;
>          cs = CPU(cpu);
>  
> @@ -897,6 +895,19 @@ void ppce500_init(MachineState *machine)
>          } else {
>              /* Secondary CPUs */
>              qemu_register_reset(ppce500_cpu_reset_sec, cpu);
> +
> +            /*
> +             * Secondary CPU starts in halted state for now. Needs to change
> +             * when implementing non-kernel boot.
> +             */
> +            object_property_set_bool(OBJECT(cs), "start-powered-off", true,
> +                                     &error_abort);
> +        }
> +
> +        if (!qdev_realize(DEVICE(cs), NULL, &err)) {
> +            error_report_err(err);
> +            object_unref(OBJECT(cs));
> +            exit(EXIT_FAILURE);
>          }

btw:
board leaks cpu reference (from cpu_create()/object_new()) since qdev_realize()
adds it's own and the caller of object_new() is suposed to free the original one.

in this case qdev_realize_and_unref() fits nicely.


>      }
>  
>