Expose thread_id in info cpus

Based on patch by Glauber Costa:

To allow management applications like libvirt to apply CPU affinities to
the VCPU threads, expose their ID via info cpus. This patch provides the
pre-existing and used interface from qemu-kvm.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

cpu-defs.h

@@ -203,6 +203,7 @@ typedef struct CPUWatchpoint {
     int nr_cores;  /* number of cores within this CPU package */        \
     int nr_threads;/* number of threads within this CPU */              \
     int running; /* Nonzero if cpu is currently running(usermode).  */  \
+    int thread_id;                                                      \
     /* user data */                                                     \
     void *opaque;                                                       \
                                                                         \

cpus.c

@@ -776,6 +776,7 @@ static void *qemu_kvm_cpu_thread_fn(void *arg)
 
     qemu_mutex_lock(&qemu_global_mutex);
     qemu_thread_get_self(env->thread);
+    env->thread_id = qemu_get_thread_id();
 
     r = kvm_init_vcpu(env);
     if (r < 0) {
@@ -817,6 +818,7 @@ static void *qemu_tcg_cpu_thread_fn(void *arg)
     /* signal CPU creation */
     qemu_mutex_lock(&qemu_global_mutex);
     for (env = first_cpu; env != NULL; env = env->next_cpu) {
+        env->thread_id = qemu_get_thread_id();
         env->created = 1;
     }
     qemu_cond_signal(&qemu_cpu_cond);

exec.c

@@ -638,6 +638,9 @@ void cpu_exec_init(CPUState *env)
     env->numa_node = 0;
     QTAILQ_INIT(&env->breakpoints);
     QTAILQ_INIT(&env->watchpoints);
+#ifndef CONFIG_USER_ONLY
+    env->thread_id = qemu_get_thread_id();
+#endif
     *penv = env;
 #if defined(CONFIG_USER_ONLY)
     cpu_list_unlock();

monitor.c

@@ -897,6 +897,9 @@ static void print_cpu_iter(QObject *obj, void *opaque)
         monitor_printf(mon, " (halted)");
     }
 
+    monitor_printf(mon, " thread_id=%" PRId64 " ",
+                   qdict_get_int(cpu, "thread_id"));
+
     monitor_printf(mon, "\n");
 }
 
@@ -941,6 +944,7 @@ static void do_info_cpus(Monitor *mon, QObject **ret_data)
 #elif defined(TARGET_MIPS)
         qdict_put(cpu, "PC", qint_from_int(env->active_tc.PC));
 #endif
+        qdict_put(cpu, "thread_id", qint_from_int(env->thread_id));
 
         qlist_append(cpu_list, cpu);
     }

os-posix.c

@@ -41,6 +41,7 @@
 
 #ifdef CONFIG_LINUX
 #include <sys/prctl.h>
+#include <sys/syscall.h>
 #endif
 
 #ifdef CONFIG_EVENTFD
@@ -382,3 +383,12 @@ int qemu_create_pidfile(const char *filename)
 
     return 0;
 }
+
+int qemu_get_thread_id(void)
+{
+#if defined (__linux__)
+    return syscall(SYS_gettid);
+#else
+    return getpid();
+#endif
+}

os-win32.c

@@ -266,3 +266,8 @@ int qemu_create_pidfile(const char *filename)
     }
     return 0;
 }
+
+int qemu_get_thread_id(void)
+{
+    return GetCurrentThreadId();
+}

osdep.h

@@ -130,5 +130,6 @@ void qemu_vfree(void *ptr);
 int qemu_madvise(void *addr, size_t len, int advice);
 
 int qemu_create_pidfile(const char *filename);
+int qemu_get_thread_id(void);
 
 #endif

qmp-commands.hx

@@ -1194,6 +1194,7 @@ Return a json-array. Each CPU is represented by a json-object, which contains:
      "nip": PPC (json-int)
      "pc" and "npc": sparc (json-int)
      "PC": mips (json-int)
+- "thread_id": ID of the underlying host thread (json-int)
 
 Example:
 
@@ -1205,12 +1206,14 @@ Example:
             "current":true,
             "halted":false,
             "pc":3227107138
+            "thread_id":3134
          },
          {
             "CPU":1,
             "current":false,
             "halted":true,
             "pc":7108165
+            "thread_id":3135
          }
       ]
    }