1 files changed, 116 insertions, 0 deletions

diff --git a/cpu-exec.c b/cpu-exec.c
index 38e5f02..cbc8067 100644
--- a/cpu-exec.c
+++ b/cpu-exec.c
@@ -22,6 +22,109 @@
 #include "tcg.h"
 #include "qemu/atomic.h"
 #include "sysemu/qtest.h"
+#include "qemu/timer.h"
+
+/* -icount align implementation. */
+
+typedef struct SyncClocks {
+    int64_t diff_clk;
+    int64_t last_cpu_icount;
+    int64_t realtime_clock;
+} SyncClocks;
+
+#if !defined(CONFIG_USER_ONLY)
+/* Allow the guest to have a max 3ms advance.
+ * The difference between the 2 clocks could therefore
+ * oscillate around 0.
+ */
+#define VM_CLOCK_ADVANCE 3000000
+#define THRESHOLD_REDUCE 1.5
+#define MAX_DELAY_PRINT_RATE 2000000000LL
+#define MAX_NB_PRINTS 100
+
+static void align_clocks(SyncClocks *sc, const CPUState *cpu)
+{
+    int64_t cpu_icount;
+
+    if (!icount_align_option) {
+        return;
+    }
+
+    cpu_icount = cpu->icount_extra + cpu->icount_decr.u16.low;
+    sc->diff_clk += cpu_icount_to_ns(sc->last_cpu_icount - cpu_icount);
+    sc->last_cpu_icount = cpu_icount;
+
+    if (sc->diff_clk > VM_CLOCK_ADVANCE) {
+#ifndef _WIN32
+        struct timespec sleep_delay, rem_delay;
+        sleep_delay.tv_sec = sc->diff_clk / 1000000000LL;
+        sleep_delay.tv_nsec = sc->diff_clk % 1000000000LL;
+        if (nanosleep(&sleep_delay, &rem_delay) < 0) {
+            sc->diff_clk -= (sleep_delay.tv_sec - rem_delay.tv_sec) * 1000000000LL;
+            sc->diff_clk -= sleep_delay.tv_nsec - rem_delay.tv_nsec;
+        } else {
+            sc->diff_clk = 0;
+        }
+#else
+        Sleep(sc->diff_clk / SCALE_MS);
+        sc->diff_clk = 0;
+#endif
+    }
+}
+
+static void print_delay(const SyncClocks *sc)
+{
+    static float threshold_delay;
+    static int64_t last_realtime_clock;
+    static int nb_prints;
+
+    if (icount_align_option &&
+        sc->realtime_clock - last_realtime_clock >= MAX_DELAY_PRINT_RATE &&
+        nb_prints < MAX_NB_PRINTS) {
+        if ((-sc->diff_clk / (float)1000000000LL > threshold_delay) ||
+            (-sc->diff_clk / (float)1000000000LL <
+             (threshold_delay - THRESHOLD_REDUCE))) {
+            threshold_delay = (-sc->diff_clk / 1000000000LL) + 1;
+            printf("Warning: The guest is now late by %.1f to %.1f seconds\n",
+                   threshold_delay - 1,
+                   threshold_delay);
+            nb_prints++;
+            last_realtime_clock = sc->realtime_clock;
+        }
+    }
+}
+
+static void init_delay_params(SyncClocks *sc,
+                              const CPUState *cpu)
+{
+    if (!icount_align_option) {
+        return;
+    }
+    sc->realtime_clock = qemu_clock_get_ns(QEMU_CLOCK_REALTIME);
+    sc->diff_clk = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) -
+                   sc->realtime_clock +
+                   cpu_get_clock_offset();
+    sc->last_cpu_icount = cpu->icount_extra + cpu->icount_decr.u16.low;
+    if (sc->diff_clk < max_delay) {
+        max_delay = sc->diff_clk;
+    }
+    if (sc->diff_clk > max_advance) {
+        max_advance = sc->diff_clk;
+    }
+
+    /* Print every 2s max if the guest is late. We limit the number
+       of printed messages to NB_PRINT_MAX(currently 100) */
+    print_delay(sc);
+}
+#else
+static void align_clocks(SyncClocks *sc, const CPUState *cpu)
+{
+}
+
+static void init_delay_params(SyncClocks *sc, const CPUState *cpu)
+{
+}
+#endif /* CONFIG USER ONLY */
 
 void cpu_loop_exit(CPUState *cpu)
 {
@@ -227,6 +330,8 @@ int cpu_exec(CPUArchState *env)
     TranslationBlock *tb;
     uint8_t *tc_ptr;
     uintptr_t next_tb;
+    SyncClocks sc;
+
     /* This must be volatile so it is not trashed by longjmp() */
     volatile bool have_tb_lock = false;
 
@@ -283,6 +388,13 @@ int cpu_exec(CPUArchState *env)
 #endif
     cpu->exception_index = -1;
 
+    /* Calculate difference between guest clock and host clock.
+     * This delay includes the delay of the last cycle, so
+     * what we have to do is sleep until it is 0. As for the
+     * advance/delay we gain here, we try to fix it next time.
+     */
+    init_delay_params(&sc, cpu);
+
     /* prepare setjmp context for exception handling */
     for(;;) {
         if (sigsetjmp(cpu->jmp_env, 0) == 0) {
@@ -672,6 +784,7 @@ int cpu_exec(CPUArchState *env)
                             if (insns_left > 0) {
                                 /* Execute remaining instructions.  */
                                 cpu_exec_nocache(env, insns_left, tb);
+                                align_clocks(&sc, cpu);
                             }
                             cpu->exception_index = EXCP_INTERRUPT;
                             next_tb = 0;
@@ -684,6 +797,9 @@ int cpu_exec(CPUArchState *env)
                     }
                 }
                 cpu->current_tb = NULL;
+                /* Try to align the host and virtual clocks
+                   if the guest is in advance */
+                align_clocks(&sc, cpu);
                 /* reset soft MMU for next block (it can currently
                    only be set by a memory fault) */
             } /* for(;;) */