use qemu_cpu_kick instead of cpu_exit or qemu_cpu_kick_thread

Use the same API to trigger interruption of a CPU, no matter if
under TCG or KVM.  There is no difference: these calls come from
the CPU thread, so the qemu_cpu_kick calls will send a signal
to the running thread and it will be processed synchronously,
just like a call to cpu_exit.  The only difference is in the
overhead, but neither call to cpu_exit (now qemu_cpu_kick)
is in a hot path.
Reviewed-by: NRichard Henderson <rth@twiddle.net>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

cpus.c

@@ -1090,6 +1090,12 @@ static void qemu_cpu_kick_thread(CPUState *cpu)
 #ifndef _WIN32
     int err;
 
+    if (!tcg_enabled()) {
+        if (cpu->thread_kicked) {
+            return;
+        }
+        cpu->thread_kicked = true;
+    }
     err = pthread_kill(cpu->thread->thread, SIG_IPI);
     if (err) {
         fprintf(stderr, "qemu:%s: %s", __func__, strerror(err));
@@ -1127,21 +1133,14 @@ static void qemu_cpu_kick_thread(CPUState *cpu)
 void qemu_cpu_kick(CPUState *cpu)
 {
     qemu_cond_broadcast(cpu->halt_cond);
-    if (!tcg_enabled() && !cpu->thread_kicked) {
-        qemu_cpu_kick_thread(cpu);
-        cpu->thread_kicked = true;
-    }
+    qemu_cpu_kick_thread(cpu);
 }
 
 void qemu_cpu_kick_self(void)
 {
 #ifndef _WIN32
     assert(current_cpu);
-
-    if (!current_cpu->thread_kicked) {
-        qemu_cpu_kick_thread(current_cpu);
-        current_cpu->thread_kicked = true;
-    }
+    qemu_cpu_kick_thread(current_cpu);
 #else
     abort();
 #endif

gdbstub.c

@@ -1362,7 +1362,7 @@ void gdb_do_syscall(gdb_syscall_complete_cb cb, const char *fmt, ...)
        is still in the running state, which can cause packets to be dropped
        and state transition 'T' packets to be sent while the syscall is still
        being processed.  */
-    cpu_exit(s->c_cpu);
+    qemu_cpu_kick(s->c_cpu);
 #endif
 }
 

hw/ppc/spapr_rtas.c

@@ -214,7 +214,7 @@ static void rtas_stop_self(PowerPCCPU *cpu, sPAPRMachineState *spapr,
     CPUPPCState *env = &cpu->env;
 
     cs->halted = 1;
-    cpu_exit(cs);
+    qemu_cpu_kick(cs);
     /*
      * While stopping a CPU, the guest calls H_CPPR which
      * effectively disables interrupts on XICS level.