Re: [Qemu-devel] [PATCH] cpu: Register QOM links at /machine/cpus/<index>

[Igor Mammedov <imammedo@redhat.com>]

On Thu, 30 Apr 2015 16:19:07 -0300
Eduardo Habkost <ehabkost@redhat.com> wrote:

> This will provide a predictable path for the CPU objects, and a more
> powerful alternative for the query-cpus QMP command, as now every QOM
> property on CPU objects can be easily queried.
provided the way cpu_index is generated, path won't be predictable/stable
with CPU unplug. I'd rather use DEVICE->id instead of cpu_index.


> 
> Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
> ---
> Note that this doesn't replace any future topology enumeration
> mechanisms we may choose to implement. It just replaces the existing
> topology-unaware VCPU enumeration mechanism that is query-cpus.
> 
> Reference to previous discussion:
> 
>   Date: Thu, 23 Apr 2015 10:17:36 -0300
>   From: Eduardo Habkost <ehabkost@redhat.com>
>   Subject: Re: [Qemu-devel] cpu modelling and hotplug (was: [PATCH RFC 0/4] target-i386: PC socket/core/thread modeling, part 1)
>   Message-ID: <20150423131736.GA17796@thinpad.lan.raisama.net>
> ---
>  exec.c            | 16 ++++++++++++++++
>  include/qom/cpu.h |  3 +++
>  2 files changed, 19 insertions(+)
> 
> diff --git a/exec.c b/exec.c
> index ae37b98..8bdfa65 100644
> --- a/exec.c
> +++ b/exec.c
> @@ -519,6 +519,20 @@ void tcg_cpu_address_space_init(CPUState *cpu, AddressSpace *as)
>  }
>  #endif
>  
> +static void cpu_add_qom_link(CPUState *cpu)
> +{
> +#if !defined(CONFIG_USER_ONLY)
> +    Object *cobj = OBJECT(cpu);
> +    Object *cpu_container = container_get(OBJECT(current_machine), "/cpus");
> +    char *path = g_strdup_printf("%d", cpu->cpu_index);
> +
> +    cpu->self = cobj;
> +    object_property_add_link(cpu_container, path, TYPE_CPU, &cpu->self, NULL,
> +                             OBJ_PROP_LINK_UNREF_ON_RELEASE, &error_abort);
> +    g_free(path);
> +#endif
> +}
> +
>  void cpu_exec_init(CPUArchState *env)
>  {
>      CPUState *cpu = ENV_GET_CPU(env);
> @@ -558,6 +572,8 @@ void cpu_exec_init(CPUArchState *env)
>      if (cc->vmsd != NULL) {
>          vmstate_register(NULL, cpu_index, cc->vmsd, cpu);
>      }
> +
> +    cpu_add_qom_link(cpu);
>  }
>  
>  #if defined(CONFIG_USER_ONLY)
> diff --git a/include/qom/cpu.h b/include/qom/cpu.h
> index 39f0f19..c253420 100644
> --- a/include/qom/cpu.h
> +++ b/include/qom/cpu.h
> @@ -246,6 +246,9 @@ struct CPUState {
>      DeviceState parent_obj;
>      /*< public >*/
>  
> +    /* Needed for the /machine/cpus/<index> link */
> +    Object *self;
> +
>      int nr_cores;
>      int nr_threads;
>      int numa_node;