qemu-timer: move timeBeginPeriod/timeEndPeriod to os-win32

These are needed for any of the Win32 alarm timer implementations.
They are not tied to mmtimer exclusively.

Jacob tested this patch with both mmtimer and Win32 timers.

Cc: qemu-stable@nongnu.org
Tested-by: Jacob Kroon <jacob.kroon@gmail.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Stefan Weil <sw@weilnetz.de>

os-win32.c

@@ -23,6 +23,7 @@
  * THE SOFTWARE.
  */
 #include <windows.h>
+#include <mmsystem.h>
 #include <unistd.h>
 #include <fcntl.h>
 #include <signal.h>
@@ -67,9 +68,19 @@ static BOOL WINAPI qemu_ctrl_handler(DWORD type)
     return TRUE;
 }
 
+static TIMECAPS mm_tc;
+
+static void os_undo_timer_resolution(void)
+{
+    timeEndPeriod(mm_tc.wPeriodMin);
+}
+
 void os_setup_early_signal_handling(void)
 {
     SetConsoleCtrlHandler(qemu_ctrl_handler, TRUE);
+    timeGetDevCaps(&mm_tc, sizeof(mm_tc));
+    timeBeginPeriod(mm_tc.wPeriodMin);
+    atexit(os_undo_timer_resolution);
 }
 
 /* Look for support files in the same directory as the executable.  */

qemu-timer.c

@@ -624,28 +624,14 @@ static void CALLBACK mm_alarm_handler(UINT uTimerID, UINT uMsg,
 static int mm_start_timer(struct qemu_alarm_timer *t)
 {
     timeGetDevCaps(&mm_tc, sizeof(mm_tc));
-
-    timeBeginPeriod(mm_tc.wPeriodMin);
-
-    mm_timer = timeSetEvent(mm_tc.wPeriodMin,   /* interval (ms) */
-                            mm_tc.wPeriodMin,   /* resolution */
-                            mm_alarm_handler,   /* function */
-                            (DWORD_PTR)t,       /* parameter */
-                            TIME_ONESHOT | TIME_CALLBACK_FUNCTION);
-
-    if (!mm_timer) {
-        fprintf(stderr, "Failed to initialize win32 alarm timer\n");
-        timeEndPeriod(mm_tc.wPeriodMin);
-        return -1;
-    }
-
     return 0;
 }
 
 static void mm_stop_timer(struct qemu_alarm_timer *t)
 {
-    timeKillEvent(mm_timer);
-    timeEndPeriod(mm_tc.wPeriodMin);
+    if (mm_timer) {
+        timeKillEvent(mm_timer);
+    }
 }
 
 static void mm_rearm_timer(struct qemu_alarm_timer *t, int64_t delta)
@@ -657,7 +643,9 @@ static void mm_rearm_timer(struct qemu_alarm_timer *t, int64_t delta)
         nearest_delta_ms = mm_tc.wPeriodMax;
     }
 
-    timeKillEvent(mm_timer);
+    if (mm_timer) {
+        timeKillEvent(mm_timer);
+    }
     mm_timer = timeSetEvent((UINT)nearest_delta_ms,
                             mm_tc.wPeriodMin,
                             mm_alarm_handler,