[uq/master,4/9] port qemu-kvm's on_vcpu code

Index: qemu/cpu-all.h
===================================================================
--- qemu.orig/cpu-all.h
+++ qemu/cpu-all.h
@@ -818,6 +818,7 @@  void cpu_watchpoint_remove_all(CPUState 
 
 void cpu_single_step(CPUState *env, int enabled);
 void cpu_reset(CPUState *s);
+void run_on_cpu(CPUState *env, void (*func)(void *data), void *data);
 
 #define CPU_LOG_TB_OUT_ASM (1 << 0)
 #define CPU_LOG_TB_IN_ASM  (1 << 1)
Index: qemu/cpu-defs.h
===================================================================
--- qemu.orig/cpu-defs.h
+++ qemu/cpu-defs.h
@@ -132,6 +132,7 @@  typedef struct icount_decr_u16 {
 
 struct kvm_run;
 struct KVMState;
+struct qemu_work_item;
 
 typedef struct CPUBreakpoint {
     target_ulong pc;
@@ -204,6 +205,7 @@  typedef struct CPUWatchpoint {
     uint32_t created;                                                   \
     struct QemuThread *thread;                                          \
     struct QemuCond *halt_cond;                                         \
+    struct qemu_work_item *queued_work_first, *queued_work_last;        \
     const char *cpu_model_str;                                          \
     struct KVMState *kvm_state;                                         \
     struct kvm_run *kvm_run;                                            \
Index: qemu/cpus.c
===================================================================
--- qemu.orig/cpus.c
+++ qemu/cpus.c
@@ -115,6 +115,8 @@  static int cpu_has_work(CPUState *env)
 {
     if (env->stop)
         return 1;
+    if (env->queued_work_first)
+        return 1;
     if (env->stopped || !vm_running)
         return 0;
     if (!env->halted)
@@ -252,6 +254,11 @@  int qemu_cpu_self(void *env)
     return 1;
 }
 
+void run_on_cpu(CPUState *env, void (*func)(void *data), void *data)
+{
+    func(data);
+}
+
 void resume_all_vcpus(void)
 {
 }
@@ -304,6 +311,7 @@  static QemuCond qemu_cpu_cond;
 /* system init */
 static QemuCond qemu_system_cond;
 static QemuCond qemu_pause_cond;
+static QemuCond qemu_work_cond;
 
 static void tcg_block_io_signals(void);
 static void kvm_block_io_signals(CPUState *env);
@@ -334,6 +342,50 @@  void qemu_main_loop_start(void)
     qemu_cond_broadcast(&qemu_system_cond);
 }
 
+void run_on_cpu(CPUState *env, void (*func)(void *data), void *data)
+{
+    struct qemu_work_item wi;
+
+    if (qemu_cpu_self(env)) {
+        func(data);
+        return;
+    }
+
+    wi.func = func;
+    wi.data = data;
+    if (!env->queued_work_first)
+        env->queued_work_first = &wi;
+    else
+        env->queued_work_last->next = &wi;
+    env->queued_work_last = &wi;
+    wi.next = NULL;
+    wi.done = false;
+
+    qemu_cpu_kick(env);
+    while (!wi.done) {
+        CPUState *self_env = cpu_single_env;
+
+        qemu_cond_wait(&qemu_work_cond, &qemu_global_mutex);
+        cpu_single_env = self_env;
+    }
+}
+
+static void flush_queued_work(CPUState *env)
+{
+    struct qemu_work_item *wi;
+
+    if (!env->queued_work_first)
+        return;
+
+    while ((wi = env->queued_work_first)) {
+        env->queued_work_first = wi->next;
+        wi->func(wi->data);
+        wi->done = true;
+    }
+    env->queued_work_last = NULL;
+    qemu_cond_broadcast(&qemu_work_cond);
+}
+
 static void qemu_wait_io_event_common(CPUState *env)
 {
     if (env->stop) {
@@ -341,6 +393,7 @@  static void qemu_wait_io_event_common(CP
         env->stopped = 1;
         qemu_cond_signal(&qemu_pause_cond);
     }
+    flush_queued_work(env);
 }
 
 static void qemu_wait_io_event(CPUState *env)
Index: qemu/qemu-common.h
===================================================================
--- qemu.orig/qemu-common.h
+++ qemu/qemu-common.h
@@ -249,6 +249,14 @@  void qemu_notify_event(void);
 void qemu_cpu_kick(void *env);
 int qemu_cpu_self(void *env);
 
+/* work queue */
+struct qemu_work_item {
+    struct qemu_work_item *next;
+    void (*func)(void *data);
+    void *data;
+    int done;
+};
+
 #ifdef CONFIG_USER_ONLY
 #define qemu_init_vcpu(env) do { } while (0)
 #else