[Qemu-devel] [patch 06/14] qemu: refactor main_loop

[mtosatti@redhat.com]

[-- Attachment #1: refactor-main-loop --]
[-- Type: text/plain, Size: 10732 bytes --]

Break main loop into 3 main functions.

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

Index: qemu-iothread-4/vl.c
===================================================================
--- qemu-iothread-4.orig/vl.c
+++ qemu-iothread-4/vl.c
@@ -266,7 +266,7 @@ struct drive_opt drives_opt[MAX_DRIVES];
 
 static CPUState *cur_cpu;
 static CPUState *next_cpu;
-static int event_pending = 1;
+static int timer_alarm_pending = 1;
 /* Conversion factor from emulated instructions to virtual clock ticks.  */
 static int icount_time_shift;
 /* Arbitrarily pick 1MIPS as the minimum allowable speed.  */
@@ -1350,7 +1350,7 @@ static void host_alarm_handler(int host_
             }
 #endif
         }
-        event_pending = 1;
+        timer_alarm_pending = 1;
         qemu_notify_event();
     }
 }
@@ -3811,153 +3811,175 @@ void main_loop_wait(int timeout)
 
 }
 
-static int main_loop(void)
+static int qemu_cpu_exec(CPUState *env)
 {
-    int ret, timeout;
+    int ret;
 #ifdef CONFIG_PROFILER
     int64_t ti;
 #endif
-    CPUState *env;
 
-    cur_cpu = first_cpu;
-    next_cpu = cur_cpu->next_cpu ?: first_cpu;
-    for(;;) {
-        if (vm_running) {
-
-            for(;;) {
-                /* get next cpu */
-                env = next_cpu;
 #ifdef CONFIG_PROFILER
-                ti = profile_getclock();
+    ti = profile_getclock();
 #endif
-                if (use_icount) {
-                    int64_t count;
-                    int decr;
-                    qemu_icount -= (env->icount_decr.u16.low + env->icount_extra);
-                    env->icount_decr.u16.low = 0;
-                    env->icount_extra = 0;
-                    count = qemu_next_deadline();
-                    count = (count + (1 << icount_time_shift) - 1)
-                            >> icount_time_shift;
-                    qemu_icount += count;
-                    decr = (count > 0xffff) ? 0xffff : count;
-                    count -= decr;
-                    env->icount_decr.u16.low = decr;
-                    env->icount_extra = count;
-                }
-                ret = cpu_exec(env);
+    if (use_icount) {
+        int64_t count;
+        int decr;
+        qemu_icount -= (env->icount_decr.u16.low + env->icount_extra);
+        env->icount_decr.u16.low = 0;
+        env->icount_extra = 0;
+        count = qemu_next_deadline();
+        count = (count + (1 << icount_time_shift) - 1)
+                >> icount_time_shift;
+        qemu_icount += count;
+        decr = (count > 0xffff) ? 0xffff : count;
+        count -= decr;
+        env->icount_decr.u16.low = decr;
+        env->icount_extra = count;
+    }
+    ret = cpu_exec(env);
 #ifdef CONFIG_PROFILER
-                qemu_time += profile_getclock() - ti;
+    qemu_time += profile_getclock() - ti;
 #endif
-                if (use_icount) {
-                    /* Fold pending instructions back into the
-                       instruction counter, and clear the interrupt flag.  */
-                    qemu_icount -= (env->icount_decr.u16.low
-                                    + env->icount_extra);
-                    env->icount_decr.u32 = 0;
-                    env->icount_extra = 0;
-                }
-                next_cpu = env->next_cpu ?: first_cpu;
-                if (event_pending && likely(ret != EXCP_DEBUG)) {
-                    ret = EXCP_INTERRUPT;
-                    event_pending = 0;
-                    break;
-                }
-                if (ret == EXCP_HLT) {
-                    /* Give the next CPU a chance to run.  */
-                    cur_cpu = env;
-                    continue;
-                }
-                if (ret != EXCP_HALTED)
+    if (use_icount) {
+        /* Fold pending instructions back into the
+           instruction counter, and clear the interrupt flag.  */
+        qemu_icount -= (env->icount_decr.u16.low
+                        + env->icount_extra);
+        env->icount_decr.u32 = 0;
+        env->icount_extra = 0;
+    }
+    return ret;
+}
+
+static int cpu_has_work(CPUState *env)
+{
+    if (!env->halted)
+        return 1;
+    if (qemu_cpu_has_work(env))
+        return 1;
+    return 0;
+}
+
+static int tcg_has_work(void)
+{
+    CPUState *env;
+
+    for (env = first_cpu; env != NULL; env = env->next_cpu)
+        if (cpu_has_work(env))
+            return 1;
+    return 0;
+}
+
+static int qemu_calculate_timeout(void)
+{
+    int timeout;
+
+    if (!vm_running)
+        timeout = 5000;
+    else if (tcg_has_work())
+        timeout = 0;
+    else if (!use_icount)
+        timeout = 5000;
+    else {
+     /* XXX: use timeout computed from timers */
+        int64_t add;
+        int64_t delta;
+        /* Advance virtual time to the next event.  */
+        if (use_icount == 1) {
+            /* When not using an adaptive execution frequency
+               we tend to get badly out of sync with real time,
+               so just delay for a reasonable amount of time.  */
+            delta = 0;
+        } else {
+            delta = cpu_get_icount() - cpu_get_clock();
+        }
+        if (delta > 0) {
+            /* If virtual time is ahead of real time then just
+               wait for IO.  */
+            timeout = (delta / 1000000) + 1;
+        } else {
+            /* Wait for either IO to occur or the next
+               timer event.  */
+            add = qemu_next_deadline();
+            /* We advance the timer before checking for IO.
+               Limit the amount we advance so that early IO
+               activity won't get the guest too far ahead.  */
+            if (add > 10000000)
+                add = 10000000;
+            delta += add;
+            add = (add + (1 << icount_time_shift) - 1)
+                  >> icount_time_shift;
+            qemu_icount += add;
+            timeout = delta / 1000000;
+            if (timeout < 0)
+                timeout = 0;
+        }
+    }
+
+    return timeout;
+}
+
+static int vm_can_run(void)
+{
+    if (powerdown_requested)
+        return 0;
+    if (reset_requested)
+        return 0;
+    if (shutdown_requested)
+        return 0;
+    return 1;
+}
+
+static void main_loop(void)
+{
+    int ret = 0;
+#ifdef CONFIG_PROFILER
+    int64_t ti;
+#endif
+
+    for (;;) {
+        do {
+            if (next_cpu == NULL)
+                next_cpu = first_cpu;
+            for (; next_cpu != NULL; next_cpu = next_cpu->next_cpu) {
+                CPUState *env = cur_cpu = next_cpu;
+
+                if (!vm_running)
                     break;
-                /* all CPUs are halted ? */
-                if (env == cur_cpu)
+                if (timer_alarm_pending) {
+                    timer_alarm_pending = 0;
                     break;
-            }
-            cur_cpu = env;
-
-            if (shutdown_requested) {
-                ret = EXCP_INTERRUPT;
-                if (no_shutdown) {
-                    vm_stop(0);
-                    no_shutdown = 0;
                 }
-                else
+                ret = qemu_cpu_exec(env);
+                if (ret == EXCP_DEBUG) {
+                    gdb_set_stop_cpu(env);
                     break;
-            }
-            if (reset_requested) {
-                reset_requested = 0;
-                qemu_system_reset();
-                ret = EXCP_INTERRUPT;
-            }
-            if (powerdown_requested) {
-                powerdown_requested = 0;
-		qemu_system_powerdown();
-                ret = EXCP_INTERRUPT;
-            }
-            if (unlikely(ret == EXCP_DEBUG)) {
-                gdb_set_stop_cpu(cur_cpu);
-                vm_stop(EXCP_DEBUG);
-            }
-            /* If all cpus are halted then wait until the next IRQ */
-            /* XXX: use timeout computed from timers */
-            if (ret == EXCP_HALTED) {
-                if (use_icount) {
-                    int64_t add;
-                    int64_t delta;
-                    /* Advance virtual time to the next event.  */
-                    if (use_icount == 1) {
-                        /* When not using an adaptive execution frequency
-                           we tend to get badly out of sync with real time,
-                           so just delay for a reasonable amount of time.  */
-                        delta = 0;
-                    } else {
-                        delta = cpu_get_icount() - cpu_get_clock();
-                    }
-                    if (delta > 0) {
-                        /* If virtual time is ahead of real time then just
-                           wait for IO.  */
-                        timeout = (delta / 1000000) + 1;
-                    } else {
-                        /* Wait for either IO to occur or the next
-                           timer event.  */
-                        add = qemu_next_deadline();
-                        /* We advance the timer before checking for IO.
-                           Limit the amount we advance so that early IO
-                           activity won't get the guest too far ahead.  */
-                        if (add > 10000000)
-                            add = 10000000;
-                        delta += add;
-                        add = (add + (1 << icount_time_shift) - 1)
-                              >> icount_time_shift;
-                        qemu_icount += add;
-                        timeout = delta / 1000000;
-                        if (timeout < 0)
-                            timeout = 0;
-                    }
-                } else {
-                    timeout = 5000;
                 }
-            } else {
-                timeout = 0;
             }
-        } else {
-            if (shutdown_requested) {
-                ret = EXCP_INTERRUPT;
-                break;
-            }
-            timeout = 5000;
-        }
 #ifdef CONFIG_PROFILER
-        ti = profile_getclock();
+            ti = profile_getclock();
 #endif
-        main_loop_wait(timeout);
+            main_loop_wait(qemu_calculate_timeout());
 #ifdef CONFIG_PROFILER
-        dev_time += profile_getclock() - ti;
+            dev_time += profile_getclock() - ti;
 #endif
+        } while (ret != EXCP_DEBUG && vm_can_run());
+
+        if (ret == EXCP_DEBUG)
+            vm_stop(EXCP_DEBUG);
+
+        if (qemu_shutdown_requested()) {
+            if (no_shutdown) {
+                vm_stop(0);
+                no_shutdown = 0;
+            } else
+                break;
+        }
+        if (qemu_reset_requested())
+            qemu_system_reset();
+        if (qemu_powerdown_requested())
+            qemu_system_powerdown();
     }
-    cpu_disable_ticks();
-    return ret;
 }
 
 static void version(void)

--