Re: [Qemu-devel] [PATCH v7 08/13] target-ppc: Introduce PowerPC specific CPU core device

[David Gibson <david@gibson.dropbear.id.au>]

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On Thu, Jan 28, 2016 at 11:19:50AM +0530, Bharata B Rao wrote:
> CPU core device is a container of CPU thread devices.  CPU hotplug is
> performed at the granularity of CPU core device. When hotplugged, CPU core
> creates CPU thread devices.
> 
> Signed-off-by: Bharata B Rao <bharata@linux.vnet.ibm.com>

The basic logic here seems fine.

However, I'm not really convinced that a "powerpc generic" device
makes sense here.  Given the diversity of powerpc platforms, it's
pretty plausible they could have very different restrictions about how
hotplug needs to operate.

So, I think it would make more sense to go for more specific devices
that either represent real hardware chips / modules, or something else
that makes sense for a specific platform.  So, in the first instance a
"PAPR virtual module" device.

It would make sense to have that derive from a more-or-less generic
base class with essentially the logic below, since even if we have
significantly different variants they're likely to share the basic
logic.  But I don't think that base type should be directly
instantiable.

Of course, once that's the case, there's really nothing ppc specific
about the base device either.

> ---
>  hw/ppc/Makefile.objs      |  1 +
>  hw/ppc/cpu-core.c         | 75 +++++++++++++++++++++++++++++++++++++++++++++++
>  include/hw/ppc/cpu-core.h | 33 +++++++++++++++++++++
>  3 files changed, 109 insertions(+)
>  create mode 100644 hw/ppc/cpu-core.c
>  create mode 100644 include/hw/ppc/cpu-core.h
> 
> diff --git a/hw/ppc/Makefile.objs b/hw/ppc/Makefile.objs
> index c1ffc77..a6b7cfb 100644
> --- a/hw/ppc/Makefile.objs
> +++ b/hw/ppc/Makefile.objs
> @@ -21,3 +21,4 @@ obj-$(CONFIG_E500) += e500.o mpc8544ds.o e500plat.o
>  obj-$(CONFIG_E500) += mpc8544_guts.o ppce500_spin.o
>  # PowerPC 440 Xilinx ML507 reference board.
>  obj-$(CONFIG_XILINX) += virtex_ml507.o
> +obj-y += cpu-core.o
> diff --git a/hw/ppc/cpu-core.c b/hw/ppc/cpu-core.c
> new file mode 100644
> index 0000000..aa96e79
> --- /dev/null
> +++ b/hw/ppc/cpu-core.c
> @@ -0,0 +1,75 @@
> +/*
> + * PowerPC CPU core device, acts as container of CPU thread devices.
> + *
> + * Copyright (C) 2016 Bharata B Rao <bharata@linux.vnet.ibm.com>
> + *
> + * This work is licensed under the terms of the GNU GPL, version 2 or later.
> + * See the COPYING file in the top-level directory.
> + */
> +#include "hw/ppc/cpu-core.h"
> +#include "hw/boards.h"
> +#include <sysemu/cpus.h>
> +#include "qemu/error-report.h"
> +
> +static int ppc_cpu_core_realize_child(Object *child, void *opaque)
> +{
> +    Error **errp = opaque;
> +
> +    object_property_set_bool(child, true, "realized", errp);
> +    if (*errp) {
> +        return 1;
> +    }
> +
> +    return 0;
> +}
> +
> +static void ppc_cpu_core_realize(DeviceState *dev, Error **errp)
> +{
> +    object_child_foreach(OBJECT(dev), ppc_cpu_core_realize_child, errp);
> +}
> +
> +static void ppc_cpu_core_class_init(ObjectClass *oc, void *data)
> +{
> +    DeviceClass *dc = DEVICE_CLASS(oc);
> +
> +    dc->realize = ppc_cpu_core_realize;
> +    dc->desc = "PowerPC CPU core";
> +}
> +
> +static void ppc_cpu_core_instance_init(Object *obj)
> +{
> +    int i;
> +    CPUState *cpu;
> +    MachineState *machine = MACHINE(qdev_get_machine());
> +    PowerPCCPUCore *core = POWERPC_CPU_CORE(obj);
> +
> +    /* Create as many CPU threads as specified in the topology */
> +    for (i = 0; i < smp_threads; i++) {
> +        cpu = cpu_generic_init(TYPE_POWERPC_CPU, machine->cpu_model);
> +        if (!cpu) {
> +            error_report("Unable to find CPU definition: %s",
> +                          machine->cpu_model);
> +            exit(EXIT_FAILURE);
> +        }
> +        object_property_add_child(obj, "thread[*]", OBJECT(cpu), &error_abort);
> +        object_unref(OBJECT(cpu));
> +        if (!i) {
> +            core->thread0 = POWERPC_CPU(cpu);
> +        }
> +    }
> +}
> +
> +static const TypeInfo ppc_cpu_core_type_info = {
> +    .name = TYPE_POWERPC_CPU_CORE,
> +    .parent = TYPE_DEVICE,
> +    .class_init = ppc_cpu_core_class_init,
> +    .instance_init = ppc_cpu_core_instance_init,
> +    .instance_size = sizeof(PowerPCCPUCore),
> +};
> +
> +static void cpu_core_register_types(void)
> +{
> +    type_register_static(&ppc_cpu_core_type_info);
> +}
> +
> +type_init(cpu_core_register_types)
> diff --git a/include/hw/ppc/cpu-core.h b/include/hw/ppc/cpu-core.h
> new file mode 100644
> index 0000000..ff2ebc2
> --- /dev/null
> +++ b/include/hw/ppc/cpu-core.h
> @@ -0,0 +1,33 @@
> +/*
> + * CPU core device.
> + *
> + * Copyright (C) 2016 Bharata B Rao <bharata@linux.vnet.ibm.com>
> + *
> + * This work is licensed under the terms of the GNU GPL, version 2 or later.
> + * See the COPYING file in the top-level directory.
> + */
> +#ifndef HW_PPC_CPU_CORE_H
> +#define HW_PPC_CPU_CORE_H
> +
> +#include "hw/qdev.h"
> +
> +#ifdef TARGET_PPC64
> +#define TYPE_POWERPC_CPU_CORE "powerpc64-cpu-core"
> +#elif defined(TARGET_PPCEMB)
> +#define TYPE_POWERPC_CPU_CORE "embedded-powerpc-cpu-core"
> +#else
> +#define TYPE_POWERPC_CPU_CORE "powerpc-cpu-core"
> +#endif
> +
> +#define POWERPC_CPU_CORE(obj) \
> +    OBJECT_CHECK(PowerPCCPUCore, (obj), TYPE_POWERPC_CPU_CORE)
> +
> +typedef struct PowerPCCPUCore {
> +    /*< private >*/
> +    DeviceState parent_obj;
> +    /*< public >*/
> +
> +    PowerPCCPU *thread0;
> +} PowerPCCPUCore;
> +
> +#endif

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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