[RFC 2/4] A separate thread for the VM migration

[Umesh Deshpande <udeshpan@xxxxxxxxxx>]

This patch implements a migration clock, whose implementation is similar to the existing rt_clock. This allows the migration timer to run in parallel to other timers in the rt_clock. In the next patch, this clock is used to create a new timer from the migration thread that calls the VM migration routine on the source side.

Signed-off-by: Umesh Deshpande <udeshpan@xxxxxxxxxx>
---
 qemu-timer.c |   29 +++++++++++++++++++++++++++--
 qemu-timer.h |    3 +++
 2 files changed, 30 insertions(+), 2 deletions(-)

diff --git a/qemu-timer.c b/qemu-timer.c
index 72066c7..91e356f 100644
--- a/qemu-timer.c
+++ b/qemu-timer.c
@@ -144,6 +144,7 @@ void cpu_disable_ticks(void)
 #define QEMU_CLOCK_REALTIME 0
 #define QEMU_CLOCK_VIRTUAL  1
 #define QEMU_CLOCK_HOST     2
+#define QEMU_CLOCK_MIGRATE  3
 
 struct QEMUClock {
     int type;
@@ -364,9 +365,10 @@ next:
     }
 }
 
-#define QEMU_NUM_CLOCKS 3
+#define QEMU_NUM_CLOCKS 4
 
 QEMUClock *rt_clock;
+QEMUClock *migration_clock;
 QEMUClock *vm_clock;
 QEMUClock *host_clock;
 
@@ -561,12 +563,31 @@ int qemu_timer_pending(QEMUTimer *ts)
     return 0;
 }
 
+int64_t qemu_timer_difference(QEMUTimer *ts, QEMUClock *clock)
+{
+    int64_t expire_time, current_time;
+    QEMUTimer *t;
+
+    current_time = qemu_get_clock_ms(clock);
+    for (t = active_timers[clock->type]; t != NULL; t = t->next) {
+        if (t == ts) {
+            expire_time = ts->expire_time / SCALE_MS;
+            if (current_time >= expire_time) {
+                return 0;
+            } else {
+                return expire_time - current_time;
+            }
+        }
+    }
+    return 0;
+}
+
 int qemu_timer_expired(QEMUTimer *timer_head, int64_t current_time)
 {
     return qemu_timer_expired_ns(timer_head, current_time * timer_head->scale);
 }
 
-static void qemu_run_timers(QEMUClock *clock)
+void qemu_run_timers(QEMUClock *clock)
 {
     QEMUTimer **ptimer_head, *ts;
     int64_t current_time;
@@ -595,6 +616,9 @@ int64_t qemu_get_clock_ns(QEMUClock *clock)
     switch(clock->type) {
     case QEMU_CLOCK_REALTIME:
         return get_clock();
+
+    case QEMU_CLOCK_MIGRATE:
+        return get_clock();
     default:
     case QEMU_CLOCK_VIRTUAL:
         if (use_icount) {
@@ -610,6 +634,7 @@ int64_t qemu_get_clock_ns(QEMUClock *clock)
 void init_clocks(void)
 {
     rt_clock = qemu_new_clock(QEMU_CLOCK_REALTIME);
+    migration_clock = qemu_new_clock(QEMU_CLOCK_MIGRATE);
     vm_clock = qemu_new_clock(QEMU_CLOCK_VIRTUAL);
     host_clock = qemu_new_clock(QEMU_CLOCK_HOST);
 
diff --git a/qemu-timer.h b/qemu-timer.h
index 06cbe20..014b70b 100644
--- a/qemu-timer.h
+++ b/qemu-timer.h
@@ -23,6 +23,7 @@ typedef void QEMUTimerCB(void *opaque);
    machine is stopped. The real time clock has a frequency of 1000
    Hz. */
 extern QEMUClock *rt_clock;
+extern QEMUClock *migration_clock;
 
 /* The virtual clock is only run during the emulation. It is stopped
    when the virtual machine is stopped. Virtual timers use a high
@@ -45,7 +46,9 @@ QEMUTimer *qemu_new_timer(QEMUClock *clock, int scale,
 void qemu_free_timer(QEMUTimer *ts);
 void qemu_del_timer(QEMUTimer *ts);
 void qemu_mod_timer(QEMUTimer *ts, int64_t expire_time);
+void qemu_run_timers(QEMUClock *clock);
 int qemu_timer_pending(QEMUTimer *ts);
+int64_t qemu_timer_difference(QEMUTimer *ts, QEMUClock *);
 int qemu_timer_expired(QEMUTimer *timer_head, int64_t current_time);
 
 void qemu_run_all_timers(void);
-- 
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