Re: [Qemu-devel] [PATCH 2/2][RFC] cpu: link each new cpu to QOM tree /machine/node/socket/core/thread/cpu respectively.

[Eduardo Habkost]

On Tue, Feb 25, 2014 at 05:07:32PM +0800, Chen Fan wrote:
> Signed-off-by: Chen Fan <address@hidden>
> ---
>  hw/i386/pc.c | 40 ++++++++++++++++++++++++++++++++++++----
>  1 file changed, 36 insertions(+), 4 deletions(-)
> 
> diff --git a/hw/i386/pc.c b/hw/i386/pc.c
> index 348b15f..4e07ef9 100644
> --- a/hw/i386/pc.c
> +++ b/hw/i386/pc.c
> @@ -57,6 +57,7 @@
>  #include "hw/boards.h"
>  #include "hw/pci/pci_host.h"
>  #include "acpi-build.h"
> +#include "qom/node.h"
>  
>  /* debug PC/ISA interrupts */
>  //#define DEBUG_IRQ
> @@ -927,11 +928,13 @@ void pc_acpi_smi_interrupt(void *opaque, int irq, int 
> level)
>      }
>  }
>  
> -static X86CPU *pc_new_cpu(const char *cpu_model, int64_t apic_id,
> +static X86CPU *pc_new_cpu(const char *cpu_model, int64_t id,
>                            DeviceState *icc_bridge, Error **errp)

What about "decoding" the CPU index as soon as possible, and making this
function get the full CPU "location", instead of adding more
CPU-index-based logic to the rest of the code?


>  {
>      X86CPU *cpu;
>      Error *local_err = NULL;
> +    Object *thread;
> +    int64_t apic_id = x86_cpu_apic_id_from_index(id);
>  
>      cpu = cpu_x86_create(cpu_model, icc_bridge, &local_err);
>      if (local_err != NULL) {
> @@ -942,11 +945,17 @@ static X86CPU *pc_new_cpu(const char *cpu_model, 
> int64_t apic_id,
>      object_property_set_int(OBJECT(cpu), apic_id, "apic-id", &local_err);
>      object_property_set_bool(OBJECT(cpu), true, "realized", &local_err);
>  
> +    thread = object_get_thread_from_index(id);

If you just separate the topo_ids_from_idx() and topo_make_apicid()
calls, the IDs calculated by topo_ids_from_idx() will be useful for two
things: 1) QOM object path construction; and 2) APIC ID calculation
(topo_make_apicid()), and you won't even need to implement
object_get_thread_from_index().

(...except when compat_apic_id_mode bug-compatibility is enabled. In
this case, either the APIC IDs won't match the QOM hierarchy, or we will
present a QOM hierarchy different from the one requested by the user.)

By the way: a hierarchical node/socket/core/thread abstraction will
probably break with current NUMA command-lines that are working. e.g.:

  $ qemu-system-x86_64 -smp 8,cores=2,threads=2 \
                       -numa node,cpus=0-2 \
                       -numa node,cpus=3-5 \
                       -numa node,cpus=6-7

The above command-line makes threads on the same socket/core appear on
different NUMA nodes. Do we want to keep this (weird) topology
configuration working?


> +    if (thread) {
> +        object_property_set_link(thread, OBJECT(cpu), "cpu", &local_err);
> +    }
> +
>      if (local_err) {
>          error_propagate(errp, local_err);
>          object_unref(OBJECT(cpu));
>          cpu = NULL;
>      }
> +
>      return cpu;
>  }
>  
> @@ -976,7 +985,29 @@ void pc_hot_add_cpu(const int64_t id, Error **errp)
>  
>      icc_bridge = DEVICE(object_resolve_path_type("icc-bridge",
>                                                   TYPE_ICC_BRIDGE, NULL));
> -    pc_new_cpu(current_cpu_model, apic_id, icc_bridge, errp);
> +    pc_new_cpu(current_cpu_model, id, icc_bridge, errp);
> +}
> +
> +static void qdev_cpus_init(void)
> +{
> +    int i, nodes;
> +    gchar *node_name;
> +    Object *obj;
> +
> +    if (nb_numa_nodes) {
> +        nodes = nb_numa_nodes;
> +    } else {
> +        nodes = 1;
> +    }
> +
> +    for (i = 0; i < nodes; i++) {
> +        obj = object_new(TYPE_NODE);
> +        node_name = g_strdup_printf("node[%" PRIi32 "]", i);
> +        object_property_add_child(qdev_get_machine(),
> +                                  node_name, obj, NULL);
> +        g_free(node_name);
> +    }
> +
>  }
>  
>  void pc_cpus_init(const char *cpu_model, DeviceState *icc_bridge)
> @@ -995,9 +1026,10 @@ void pc_cpus_init(const char *cpu_model, DeviceState 
> *icc_bridge)
>      }
>      current_cpu_model = cpu_model;
>  
> +    qdev_cpus_init();
> +
>      for (i = 0; i < smp_cpus; i++) {
> -        cpu = pc_new_cpu(cpu_model, x86_cpu_apic_id_from_index(i),
> -                         icc_bridge, &error);
> +        cpu = pc_new_cpu(cpu_model, i, icc_bridge, &error);
>          if (error) {
>              error_report("%s", error_get_pretty(error));
>              error_free(error);
> -- 
> 1.8.1.4
> 

-- 
Eduardo