[Qemu-devel] [RFC PATCH v4 04/13] icount: introduce icount timer.

[fred.konrad@greensocs.com]

From: KONRAD Frederic <fred.konrad@greensocs.com>

This introduces a new timer based only on instruction counter and without any
compensation.

Signed-off-by: KONRAD Frederic <fred.konrad@greensocs.com>
---
 cpus.c                 | 19 ++++++++++++-------
 include/qemu/timer.h   |  9 ++++++++-
 qemu-timer.c           |  8 +++++++-
 stubs/cpu-get-icount.c |  2 +-
 4 files changed, 28 insertions(+), 10 deletions(-)

diff --git a/cpus.c b/cpus.c
index 8d2ddf0..7f99d5e 100644
--- a/cpus.c
+++ b/cpus.c
@@ -134,7 +134,7 @@ typedef struct TimersState {
 static TimersState timers_state;
 
 /* Return the virtual CPU time, based on the instruction counter.  */
-static int64_t cpu_get_icount_locked(void)
+static int64_t cpu_get_icount_locked(int with_bias)
 {
     int64_t icount;
     CPUState *cpu = current_cpu;
@@ -146,17 +146,22 @@ static int64_t cpu_get_icount_locked(void)
         }
         icount -= (cpu->icount_decr.u16.low + cpu->icount_extra);
     }
-    return timers_state.qemu_icount_bias + (icount << icount_time_shift);
+
+    if (with_bias) {
+        return timers_state.qemu_icount_bias + (icount << icount_time_shift);
+    } else {
+        return icount << icount_time_shift;
+    }
 }
 
-int64_t cpu_get_icount(void)
+int64_t cpu_get_icount(int with_bias)
 {
     int64_t icount;
     unsigned start;
 
     do {
         start = seqlock_read_begin(&timers_state.vm_clock_seqlock);
-        icount = cpu_get_icount_locked();
+        icount = cpu_get_icount_locked(with_bias);
     } while (seqlock_read_retry(&timers_state.vm_clock_seqlock, start));
 
     return icount;
@@ -169,7 +174,7 @@ int64_t cpu_get_ticks(void)
     int64_t ticks;
 
     if (use_icount) {
-        return cpu_get_icount();
+        return cpu_get_icount(true);
     }
 
     ticks = timers_state.cpu_ticks_offset;
@@ -267,7 +272,7 @@ static void icount_adjust(void)
 
     seqlock_write_lock(&timers_state.vm_clock_seqlock);
     cur_time = cpu_get_clock_locked();
-    cur_icount = cpu_get_icount_locked();
+    cur_icount = cpu_get_icount_locked(true);
 
     delta = cur_icount - cur_time;
     /* FIXME: This is a very crude algorithm, somewhat prone to oscillation.  */
@@ -330,7 +335,7 @@ static void icount_warp_rt(void *opaque)
              * far ahead of real time.
              */
             int64_t cur_time = cpu_get_clock_locked();
-            int64_t cur_icount = cpu_get_icount_locked();
+            int64_t cur_icount = cpu_get_icount_locked(true);
             int64_t delta = cur_time - cur_icount;
             warp_delta = MIN(warp_delta, delta);
         }
diff --git a/include/qemu/timer.h b/include/qemu/timer.h
index 7f9a074..6204cab 100644
--- a/include/qemu/timer.h
+++ b/include/qemu/timer.h
@@ -36,12 +36,19 @@
  * is suspended, and it will reflect system time changes the host may
  * undergo (e.g. due to NTP). The host clock has the same precision as
  * the virtual clock.
+ *
+ * @QEMU_CLOCK_ICOUNT: icount clock
+ *
+ * The icount clock is based on instruction counter without any compensation for
+ * speed. It will run only when instruction are executed and make only sense in
+ * icount mode.
  */
 
 typedef enum {
     QEMU_CLOCK_REALTIME = 0,
     QEMU_CLOCK_VIRTUAL = 1,
     QEMU_CLOCK_HOST = 2,
+    QEMU_CLOCK_ICOUNT = 3,
     QEMU_CLOCK_MAX
 } QEMUClockType;
 
@@ -743,7 +750,7 @@ static inline int64_t get_clock(void)
 #endif
 
 /* icount */
-int64_t cpu_get_icount(void);
+int64_t cpu_get_icount(int with_bias);
 int64_t cpu_get_clock(void);
 
 /*******************************************/
diff --git a/qemu-timer.c b/qemu-timer.c
index 00a5d35..3be80b1 100644
--- a/qemu-timer.c
+++ b/qemu-timer.c
@@ -554,7 +554,7 @@ int64_t qemu_clock_get_ns(QEMUClockType type)
     default:
     case QEMU_CLOCK_VIRTUAL:
         if (use_icount) {
-            return cpu_get_icount();
+            return cpu_get_icount(true);
         } else {
             return cpu_get_clock();
         }
@@ -566,6 +566,12 @@ int64_t qemu_clock_get_ns(QEMUClockType type)
             notifier_list_notify(&clock->reset_notifiers, &now);
         }
         return now;
+    case QEMU_CLOCK_ICOUNT:
+        if (use_icount) {
+            return cpu_get_icount(false);
+        } else {
+            return -1;
+        }
     }
 }
 
diff --git a/stubs/cpu-get-icount.c b/stubs/cpu-get-icount.c
index d685859..1968de7 100644
--- a/stubs/cpu-get-icount.c
+++ b/stubs/cpu-get-icount.c
@@ -3,7 +3,7 @@
 
 int use_icount;
 
-int64_t cpu_get_icount(void)
+int64_t cpu_get_icount(int with_bias)
 {
     abort();
 }
-- 
1.9.0