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

[Eduardo Habkost <ehabkost@redhat.com>]

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.

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;
-- 
2.1.0