[16/18] cpu: Allow pausing and resuming CPUs in qemu-user

diff --git a/accel/tcg/user-exec-stub.c b/accel/tcg/user-exec-stub.c
index 4fbe2dbdc88..e79f2e88498 100644
--- a/accel/tcg/user-exec-stub.c
+++ b/accel/tcg/user-exec-stub.c
@@ -2,10 +2,6 @@ 
 #include "hw/core/cpu.h"
 #include "exec/replay-core.h"
 
-void cpu_resume(CPUState *cpu)
-{
-}
-
 void cpu_remove_sync(CPUState *cpu)
 {
 }
diff --git a/accel/tcg/user-exec.c b/accel/tcg/user-exec.c
index de4753cded7..3399b074485 100644
--- a/accel/tcg/user-exec.c
+++ b/accel/tcg/user-exec.c
@@ -1293,12 +1293,19 @@  int cpu_exec_user(CPUState *cs)
 {
     int trapnr;
 
+    do {
+        qemu_wait_io_event(cs);
+    } while (!cpu_can_run(cs));
+
     bql_unlock();
     cpu_exec_start(cs);
     trapnr = cpu_exec(cs);
     cpu_exec_end(cs);
     bql_lock();
-    process_queued_cpu_work(cs);
+
+    do {
+        qemu_wait_io_event(cs);
+    } while (!cpu_can_run(cs));
 
     return trapnr;
 }
@@ -1306,11 +1313,13 @@  int cpu_exec_user(CPUState *cs)
 void qemu_cpu_kick(CPUState *cpu)
 {
     cpu_exit(cpu);
+    qemu_cond_broadcast(cpu->halt_cond);
 }
 
 void cpu_enter_syscall(CPUState *cs)
 {
     cs->in_syscall = true;
+    qemu_pause_cond_broadcast();
 }
 
 void cpu_exit_syscall(CPUState *cs)
diff --git a/cpu-common.c b/cpu-common.c
index 2822ee9373d..979e3fe8806 100644
--- a/cpu-common.c
+++ b/cpu-common.c
@@ -24,6 +24,8 @@ 
 #include "sysemu/cpus.h"
 #include "qemu/lockable.h"
 #include "trace/trace-root.h"
+#include "exec/replay-core.h"
+#include "qemu/plugin.h"
 
 QemuMutex qemu_cpu_list_lock;
 static QemuCond exclusive_cond;
@@ -456,6 +458,9 @@  void cpu_breakpoint_remove_all(CPUState *cpu, int mask)
 /* The Big QEMU Lock (BQL) */
 static QemuMutex bql = QEMU_MUTEX_INITIALIZER;
 
+/* system init */
+static QemuCond qemu_pause_cond = QEMU_COND_INITIALIZER;
+
 QEMU_DEFINE_STATIC_CO_TLS(bool, bql_locked)
 
 bool bql_locked(void)
@@ -498,6 +503,105 @@  void run_on_cpu(CPUState *cpu, run_on_cpu_func func, run_on_cpu_data data)
     do_run_on_cpu(cpu, func, data, &bql);
 }
 
+static bool all_vcpus_paused(void)
+{
+    CPUState *cpu;
+
+    CPU_FOREACH(cpu) {
+        if (!cpu_is_paused(cpu)) {
+            return false;
+        }
+    }
+
+    return true;
+}
+
+void pause_all_vcpus(void)
+{
+    CPUState *cpu;
+
+    qemu_clock_enable(QEMU_CLOCK_VIRTUAL, false);
+    CPU_FOREACH(cpu) {
+        cpu_pause(cpu);
+    }
+
+    /* We need to drop the replay_lock so any vCPU threads woken up
+     * can finish their replay tasks
+     */
+    replay_mutex_unlock();
+
+    while (!all_vcpus_paused()) {
+        qemu_cond_wait_bql(&qemu_pause_cond);
+        CPU_FOREACH(cpu) {
+            qemu_cpu_kick(cpu);
+        }
+    }
+
+    bql_unlock();
+    replay_mutex_lock();
+    bql_lock();
+}
+
+void qemu_pause_cond_broadcast(void)
+{
+    qemu_cond_broadcast(&qemu_pause_cond);
+}
+
+static void qemu_cpu_stop(CPUState *cpu, bool exit)
+{
+    g_assert(qemu_cpu_is_self(cpu));
+    cpu->stop = false;
+    cpu->stopped = true;
+    if (exit) {
+        cpu_exit(cpu);
+    }
+    qemu_pause_cond_broadcast();
+}
+
+void qemu_wait_io_event_common(CPUState *cpu)
+{
+    qatomic_set_mb(&cpu->thread_kicked, false);
+    if (cpu->stop) {
+        qemu_cpu_stop(cpu, false);
+    }
+    process_queued_cpu_work(cpu);
+}
+
+void qemu_wait_io_event(CPUState *cpu)
+{
+    bool slept = false;
+
+    while (cpu_thread_is_idle(cpu)) {
+        if (!slept) {
+            slept = true;
+            qemu_plugin_vcpu_idle_cb(cpu);
+        }
+        qemu_cond_wait_bql(cpu->halt_cond);
+    }
+    if (slept) {
+        qemu_plugin_vcpu_resume_cb(cpu);
+    }
+
+    qemu_wait_io_event_common(cpu);
+}
+
+void cpu_pause(CPUState *cpu)
+{
+    if (qemu_cpu_is_self(cpu)) {
+        qemu_cpu_stop(cpu, true);
+    } else {
+        cpu->stop = true;
+        qemu_cpu_kick(cpu);
+    }
+}
+
+void cpu_resume(CPUState *cpu)
+{
+    cpu->stop = false;
+    cpu->stopped = false;
+    qemu_cpu_kick(cpu);
+}
+
 bool cpu_work_list_empty(CPUState *cpu)
 {
     return QSIMPLEQ_EMPTY_ATOMIC(&cpu->work_list);
@@ -516,3 +620,14 @@  int cpu_thread_is_idle_common(CPUState *cpu)
     }
     return -1;
 }
+
+bool cpu_can_run(CPUState *cpu)
+{
+    if (cpu->stop) {
+        return false;
+    }
+    if (cpu_is_stopped(cpu)) {
+        return false;
+    }
+    return true;
+}
diff --git a/include/exec/cpu-common.h b/include/exec/cpu-common.h
index e8b530ed889..a54368c5b69 100644
--- a/include/exec/cpu-common.h
+++ b/include/exec/cpu-common.h
@@ -234,6 +234,13 @@  void cpu_exit_syscall(CPUState *cs);
 int cpu_thread_is_idle_common(CPUState *cpu);
 bool cpu_thread_is_idle(CPUState *cpu);
 bool cpu_is_paused(CPUState *cpu);
+bool cpu_can_run(CPUState *cpu);
+void qemu_wait_io_event_common(CPUState *cpu);
+void qemu_wait_io_event(CPUState *cpu);
+void pause_all_vcpus(void);
+void qemu_pause_cond_broadcast(void);
+bool cpu_work_list_empty(CPUState *cpu);
+
 
 /**
  * env_archcpu(env)
diff --git a/include/sysemu/cpus.h b/include/sysemu/cpus.h
index bfa3fd45650..ebfd0b77bcd 100644
--- a/include/sysemu/cpus.h
+++ b/include/sysemu/cpus.h
@@ -20,11 +20,7 @@  void dummy_start_vcpu_thread(CPUState *);
 #define VCPU_THREAD_NAME_SIZE 16
 
 void cpus_kick_thread(CPUState *cpu);
-bool cpu_work_list_empty(CPUState *cpu);
 bool all_cpu_threads_idle(void);
-bool cpu_can_run(CPUState *cpu);
-void qemu_wait_io_event_common(CPUState *cpu);
-void qemu_wait_io_event(CPUState *cpu);
 void cpu_thread_signal_created(CPUState *cpu);
 void cpu_thread_signal_destroyed(CPUState *cpu);
 void cpu_handle_guest_debug(CPUState *cpu);
@@ -34,7 +30,6 @@  void cpu_handle_guest_debug(CPUState *cpu);
 bool qemu_in_vcpu_thread(void);
 void qemu_init_cpu_loop(void);
 void resume_all_vcpus(void);
-void pause_all_vcpus(void);
 void cpu_stop_current(void);
 
 extern int icount_align_option;
diff --git a/system/cpus.c b/system/cpus.c
index 407140c41f6..9ad7bae056e 100644
--- a/system/cpus.c
+++ b/system/cpus.c
@@ -307,17 +307,6 @@  int vm_shutdown(void)
     return do_vm_stop(RUN_STATE_SHUTDOWN, false);
 }
 
-bool cpu_can_run(CPUState *cpu)
-{
-    if (cpu->stop) {
-        return false;
-    }
-    if (cpu_is_stopped(cpu)) {
-        return false;
-    }
-    return true;
-}
-
 void cpu_handle_guest_debug(CPUState *cpu)
 {
     if (replay_running_debug()) {
@@ -400,56 +389,15 @@  static QemuThread io_thread;
 
 /* cpu creation */
 static QemuCond qemu_cpu_cond;
-/* system init */
-static QemuCond qemu_pause_cond;
 
 void qemu_init_cpu_loop(void)
 {
     qemu_init_sigbus();
     qemu_cond_init(&qemu_cpu_cond);
-    qemu_cond_init(&qemu_pause_cond);
 
     qemu_thread_get_self(&io_thread);
 }
 
-static void qemu_cpu_stop(CPUState *cpu, bool exit)
-{
-    g_assert(qemu_cpu_is_self(cpu));
-    cpu->stop = false;
-    cpu->stopped = true;
-    if (exit) {
-        cpu_exit(cpu);
-    }
-    qemu_cond_broadcast(&qemu_pause_cond);
-}
-
-void qemu_wait_io_event_common(CPUState *cpu)
-{
-    qatomic_set_mb(&cpu->thread_kicked, false);
-    if (cpu->stop) {
-        qemu_cpu_stop(cpu, false);
-    }
-    process_queued_cpu_work(cpu);
-}
-
-void qemu_wait_io_event(CPUState *cpu)
-{
-    bool slept = false;
-
-    while (cpu_thread_is_idle(cpu)) {
-        if (!slept) {
-            slept = true;
-            qemu_plugin_vcpu_idle_cb(cpu);
-        }
-        qemu_cond_wait_bql(cpu->halt_cond);
-    }
-    if (slept) {
-        qemu_plugin_vcpu_resume_cb(cpu);
-    }
-
-    qemu_wait_io_event_common(cpu);
-}
-
 void cpus_kick_thread(CPUState *cpu)
 {
     if (cpu->thread_kicked) {
@@ -513,67 +461,11 @@  void cpu_thread_signal_destroyed(CPUState *cpu)
     qemu_cond_signal(&qemu_cpu_cond);
 }
 
-void cpu_pause(CPUState *cpu)
-{
-    if (qemu_cpu_is_self(cpu)) {
-        qemu_cpu_stop(cpu, true);
-    } else {
-        cpu->stop = true;
-        qemu_cpu_kick(cpu);
-    }
-}
-
-void cpu_resume(CPUState *cpu)
-{
-    cpu->stop = false;
-    cpu->stopped = false;
-    qemu_cpu_kick(cpu);
-}
-
 bool cpu_is_paused(CPUState *cpu)
 {
     return cpu->stopped;
 }
 
-static bool all_vcpus_paused(void)
-{
-    CPUState *cpu;
-
-    CPU_FOREACH(cpu) {
-        if (!cpu_is_paused(cpu)) {
-            return false;
-        }
-    }
-
-    return true;
-}
-
-void pause_all_vcpus(void)
-{
-    CPUState *cpu;
-
-    qemu_clock_enable(QEMU_CLOCK_VIRTUAL, false);
-    CPU_FOREACH(cpu) {
-        cpu_pause(cpu);
-    }
-
-    /* We need to drop the replay_lock so any vCPU threads woken up
-     * can finish their replay tasks
-     */
-    replay_mutex_unlock();
-
-    while (!all_vcpus_paused()) {
-        qemu_cond_wait_bql(&qemu_pause_cond);
-        CPU_FOREACH(cpu) {
-            qemu_cpu_kick(cpu);
-        }
-    }
-
-    bql_unlock();
-    replay_mutex_lock();
-    bql_lock();
-}
-
 void resume_all_vcpus(void)
 {
     CPUState *cpu;