Re: [Qemu-devel] [RFC 08/13] pc: add writeonly 'cpu' property to PCMachine

[Eduardo Habkost]

On Wed, Jan 18, 2017 at 06:13:24PM +0100, Igor Mammedov wrote:
> it will allow generic numa code to set cpu to numa node mapping
> in target independent manner in the next patch.
> 
> Signed-off-by: Igor Mammedov <address@hidden>
> ---
>  hw/i386/pc.c | 56 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 56 insertions(+)
> 
> diff --git a/hw/i386/pc.c b/hw/i386/pc.c
> index f8ea635..1d33a5e 100644
> --- a/hw/i386/pc.c
> +++ b/hw/i386/pc.c
> @@ -2201,6 +2201,56 @@ static void pc_machine_set_pit(Object *obj, bool 
> value, Error **errp)
>      pcms->pit = value;
>  }
>  
> +static void pc_machine_set_cpu(Object *obj, Visitor *v, const char *name,
> +                               void *opaque, Error **errp)
> +{
> +    uint32_t apic_id;
> +    X86CPUTopoInfo topo;
> +    CPUArchId *cpu_slot;
> +    Error *local_err = NULL;
> +    CpuInstanceProperties *cpu_props = NULL;
> +    PCMachineState *pcms = PC_MACHINE(obj);
> +    MachineClass *mc = MACHINE_GET_CLASS(obj);
> +
> +    visit_type_CpuInstanceProperties(v, name, &cpu_props, &local_err);
> +    if (local_err) {
> +        goto out;
> +    }
> +
> +    if (!cpu_props->has_node_id) {
> +        error_setg(&local_err, "node-id property is not specified");
> +        goto out;
> +    }
> +
> +    /*
> +     * make sure that possible_cpus is initialized
> +     * as property setter might be called before machine init is called
> +     */
> +    mc->possible_cpu_arch_ids(MACHINE(obj));
> +
> +    topo.pkg_id = cpu_props->socket_id;
> +    topo.core_id = cpu_props->core_id;
> +    topo.smt_id = cpu_props->thread_id;
> +    apic_id = apicid_from_topo_ids(smp_cores, smp_threads, &topo);
> +    cpu_slot = pc_find_cpu_slot(pcms, apic_id, NULL);

If we make TYPE_MACHINE provide an API to query CPU slots, e.g.:
  CPUArchId *machine_find_cpu_slot(MachineState *m, CpuInstanceProperties 
*props)
  CPUArchId *machine_slot_for_cpu(MachineState *m, CPUState *cpu)

(Which can probably be implemented using
MachineClass::possible_cpu_arch_ids(), already)

Then this function could be implemented in a generic way, and all
existing calls of:
  numa_get_node_for_cpu(cpu->cpu_index)
could be easily replaced by:
  machine_slot_for_cpu(cpu)->props.node_id

This should make it easier to get rid numa_info[].node_cpu.

> +    if (!cpu_slot) {
> +        error_setg(&local_err, "unable to find CPU");
> +        goto out;
> +    }
> +
> +    if (cpu_slot->props.has_node_id) {
> +        error_setg(&local_err, "CPU has already been assigned to node: 
> %"PRId64,
> +                   cpu_slot->props.node_id);
> +        goto out;
> +    }
> +    cpu_slot->props.has_node_id = true;
> +    cpu_slot->props.node_id = cpu_props->node_id;
> +
> + out:
> +    error_propagate(errp, local_err);
> +    qapi_free_CpuInstanceProperties(cpu_props);
> +}
> +
>  static void pc_machine_initfn(Object *obj)
>  {
>      PCMachineState *pcms = PC_MACHINE(obj);
> @@ -2395,6 +2445,12 @@ static void pc_machine_class_init(ObjectClass *oc, 
> void *data)
>  
>      object_class_property_add_bool(oc, PC_MACHINE_PIT,
>          pc_machine_get_pit, pc_machine_set_pit, &error_abort);
> +
> +    object_class_property_add(oc, "cpu", "CpuInstanceProperties",
> +        NULL, pc_machine_set_cpu,
> +        NULL, NULL, &error_abort);
> +    object_class_property_set_description(oc, "cpu",
> +        "Possible cpu placement", &error_abort);
>  }
>  
>  static const TypeInfo pc_machine_info = {
> -- 
> 2.7.4
> 

-- 
Eduardo