Re: [PATCH v4 5/8] mips/cps: Use start-powered-off CPUState property

[Philippe Mathieu-Daudé]

On 8/18/20 5:33 AM, Thiago Jung Bauermann wrote:
> Instead of setting CPUState::halted to 1 in main_cpu_reset(), use the
> start-powered-off property which makes cpu_common_reset() initialize it
> to 1 in common code.
> 
> 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.
> 
> Signed-off-by: Thiago Jung Bauermann <bauerman@linux.ibm.com>
> ---
>  hw/mips/cps.c | 16 ++++++++++++----
>  1 file changed, 12 insertions(+), 4 deletions(-)
> 
> diff --git a/hw/mips/cps.c b/hw/mips/cps.c
> index 615e1a1ad2..be85357dc0 100644
> --- a/hw/mips/cps.c
> +++ b/hw/mips/cps.c
> @@ -52,9 +52,6 @@ static void main_cpu_reset(void *opaque)
>      CPUState *cs = CPU(cpu);
>  
>      cpu_reset(cs);
> -
> -    /* All VPs are halted on reset. Leave powering up to CPC. */
> -    cs->halted = 1;
>  }
>  
>  static bool cpu_mips_itu_supported(CPUMIPSState *env)
> @@ -76,7 +73,9 @@ static void mips_cps_realize(DeviceState *dev, Error **errp)
>      bool saar_present = false;
>  
>      for (i = 0; i < s->num_vp; i++) {
> -        cpu = MIPS_CPU(cpu_create(s->cpu_type));
> +        Error *err = NULL;
> +
> +        cpu = MIPS_CPU(object_new(s->cpu_type));
>  
>          /* Init internal devices */
>          cpu_mips_irq_init_cpu(cpu);
> @@ -89,7 +88,16 @@ static void mips_cps_realize(DeviceState *dev, Error 
> **errp)
>              env->itc_tag = mips_itu_get_tag_region(&s->itu);
>              env->itu = &s->itu;
>          }
> +        /* All VPs are halted on reset. Leave powering up to CPC. */
> +        object_property_set_bool(OBJECT(cpu), "start-powered-off", true,
> +                                 &error_abort);
>          qemu_register_reset(main_cpu_reset, cpu);
> +
> +        if (!qdev_realize(DEVICE(cpu), NULL, &err)) {
> +            error_report_err(err);
> +            object_unref(OBJECT(cpu));
> +            exit(EXIT_FAILURE);
> +        }

Here errp is available, so we can propagate the error to the caller:

           if (!qdev_realize(DEVICE(cpu), NULL, errp)) {
               return;
           }

For example in hw/mips/boston.c:

    object_initialize_child(OBJECT(machine), "cps", &s->cps, TYPE_MIPS_CPS);
    object_property_set_str(OBJECT(&s->cps), "cpu-type", machine->cpu_type,
                            &error_fatal);
    object_property_set_int(OBJECT(&s->cps), "num-vp", machine->smp.cpus,
                            &error_fatal);
    sysbus_realize(SYS_BUS_DEVICE(&s->cps), &error_fatal);

This will be propagated here ---------------^^^^^^^^^^^^^

>      }
>  
>      cpu = MIPS_CPU(first_cpu);
>