‘-icount [N|auto]’

    Enable virtual instruction counter. The virtual cpu will
execute one instruction every 2^N ns of virtual time. If auto is
specified then the virtual cpu speed will be automatically
adjusted to keep virtual time within a few seconds of real time.

    Note that while this option can give deterministic behavior,
it does not provide cycle accurate emulation. Modern CPUs
contain superscalar out of order cores with complex cache
hierarchies. The number of instructions executed often has
little or no correlation with actual performance. 

diff --git a/include/qemu/timer.h b/include/qemu/timer.h
index 7f9a074..31826ca 100644
--- a/include/qemu/timer.h
+++ b/include/qemu/timer.h
@@ -7,6 +7,8 @@
 
 /* timers */
 
+#define SLOWDOWN 2
+
 #define SCALE_MS 1000000
 #define SCALE_US 1000
 #define SCALE_NS 1
diff --git a/qemu-timer.c b/qemu-timer.c
index 00a5d35..2933473 100644
--- a/qemu-timer.c
+++ b/qemu-timer.c
@@ -550,13 +550,13 @@ int64_t qemu_clock_get_ns(QEMUClockType type)
 
     switch (type) {
     case QEMU_CLOCK_REALTIME:
-        return get_clock();
+        return get_clock() / SLOWDOWN;
     default:
     case QEMU_CLOCK_VIRTUAL:
         if (use_icount) {
-            return cpu_get_icount();
+            return cpu_get_icount() / SLOWDOWN;
         } else {
-            return cpu_get_clock();
+            return cpu_get_clock() / SLOWDOWN;
         }
     case QEMU_CLOCK_HOST:
         now = get_clock_realtime();
diff --git a/target-i386/cpu.c b/target-i386/cpu.c
index f9fcbca..3ce6499 100644
--- a/target-i386/cpu.c
+++ b/target-i386/cpu.c
@@ -448,13 +448,13 @@ typedef struct model_features_t {
  * when KVM is enabled.
  */
 static uint32_t kvm_default_features[FEATURE_WORDS] = {
-    [FEAT_KVM] = (1 << KVM_FEATURE_CLOCKSOURCE) |
+    [FEAT_KVM] = /*(1 << KVM_FEATURE_CLOCKSOURCE) |*/
         (1 << KVM_FEATURE_NOP_IO_DELAY) |
-        (1 << KVM_FEATURE_CLOCKSOURCE2) |
+        /*(1 << KVM_FEATURE_CLOCKSOURCE2) |*/
         (1 << KVM_FEATURE_ASYNC_PF) |
         (1 << KVM_FEATURE_STEAL_TIME) |
-        (1 << KVM_FEATURE_PV_EOI) |
-        (1 << KVM_FEATURE_CLOCKSOURCE_STABLE_BIT),
+        (1 << KVM_FEATURE_PV_EOI) /*|
+        (1 << KVM_FEATURE_CLOCKSOURCE_STABLE_BIT)*/,
     [FEAT_1_ECX] = CPUID_EXT_X2APIC,
 };
 
diff --git a/target-i386/kvm.c b/target-i386/kvm.c
index ddedc73..3918cef 100644
--- a/target-i386/kvm.c
+++ b/target-i386/kvm.c
@@ -131,7 +131,7 @@ static const struct kvm_para_features {
     int cap;
     int feature;
 } para_features[] = {
-    { KVM_CAP_CLOCKSOURCE, KVM_FEATURE_CLOCKSOURCE },
+    /*{ KVM_CAP_CLOCKSOURCE, KVM_FEATURE_CLOCKSOURCE },*/
     { KVM_CAP_NOP_IO_DELAY, KVM_FEATURE_NOP_IO_DELAY },
     { KVM_CAP_PV_MMU, KVM_FEATURE_MMU_OP },
     { KVM_CAP_ASYNC_PF, KVM_FEATURE_ASYNC_PF },

$ cat /sys/devices/system/clocksource/clocksource0/available_clocksource 
tsc hpet acpi_pm 

From 3dc4c83590cb4eab4d50f3329bedb8b1a4f4e961 Mon Sep 17 00:00:00 2001
From: Ivan Mironov <mironov.ivan@gmail.com>
Date: Thu, 13 Nov 2014 12:30:52 +0300
Subject: [PATCH] WIP: slowtime

---
 include/qemu/timer.h |  2 ++
 qemu-options.hx      |  6 ++++++
 qemu-timer.c         |  8 +++++---
 target-i386/cpu.c    | 15 +++++++++++++++
 vl.c                 | 24 ++++++++++++++++++++++++
 5 files changed, 52 insertions(+), 3 deletions(-)

diff --git a/include/qemu/timer.h b/include/qemu/timer.h
index 7f9a074..7290a8b 100644
--- a/include/qemu/timer.h
+++ b/include/qemu/timer.h
@@ -7,6 +7,8 @@
 
 /* timers */
 
+extern int32_t slowtime_divider;
+
 #define SCALE_MS 1000000
 #define SCALE_US 1000
 #define SCALE_NS 1
diff --git a/qemu-options.hx b/qemu-options.hx
index 1549625..1eb5c83 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -3352,3 +3352,9 @@ HXCOMM This is the last statement. Insert new options before this line!
 STEXI
 @end table
 ETEXI
+
+
+DEF("slowtime", HAS_ARG, QEMU_OPTION_slowtime, \
+    "-slowtime divider=number\n" \
+    "                slow down system clock\n",
+    QEMU_ARCH_ALL)
diff --git a/qemu-timer.c b/qemu-timer.c
index 00a5d35..ce95db8 100644
--- a/qemu-timer.c
+++ b/qemu-timer.c
@@ -41,6 +41,8 @@
 #include <sys/prctl.h>
 #endif
 
+int32_t slowtime_divider = 1;
+
 /***********************************************************/
 /* timers */
 
@@ -550,13 +552,13 @@ int64_t qemu_clock_get_ns(QEMUClockType type)
 
     switch (type) {
     case QEMU_CLOCK_REALTIME:
-        return get_clock();
+        return get_clock() / slowtime_divider;
     default:
     case QEMU_CLOCK_VIRTUAL:
         if (use_icount) {
-            return cpu_get_icount();
+            return cpu_get_icount() / slowtime_divider;
         } else {
-            return cpu_get_clock();
+            return cpu_get_clock() / slowtime_divider;
         }
     case QEMU_CLOCK_HOST:
         now = get_clock_realtime();
diff --git a/target-i386/cpu.c b/target-i386/cpu.c
index f9fcbca..23d9627 100644
--- a/target-i386/cpu.c
+++ b/target-i386/cpu.c
@@ -31,6 +31,8 @@
 #include "qemu/config-file.h"
 #include "qapi/qmp/qerror.h"
 
+#include "qemu/timer.h"
+
 #include "qapi-types.h"
 #include "qapi-visit.h"
 #include "qapi/visitor.h"
@@ -1994,6 +1996,13 @@ static void x86_cpu_load_def(X86CPU *cpu, X86CPUDefinition *def, Error **errp)
     /* Special cases not set in the X86CPUDefinition structs: */
     if (kvm_enabled()) {
         FeatureWord w;
+
+        if (slowtime_divider != 1) {
+            kvm_default_features[FEAT_KVM] &= ~KVM_FEATURE_CLOCKSOURCE;
+            kvm_default_features[FEAT_KVM] &= ~KVM_FEATURE_CLOCKSOURCE_STABLE_BIT;
+            kvm_default_features[FEAT_KVM] &= ~KVM_FEATURE_CLOCKSOURCE2;
+        }
+
         for (w = 0; w < FEATURE_WORDS; w++) {
             env->features[w] |= kvm_default_features[w];
             env->features[w] &= ~kvm_default_unset_features[w];
@@ -2738,6 +2747,12 @@ static void x86_cpu_realizefn(DeviceState *dev, Error **errp)
     }
 #endif
 
+    if (slowtime_divider != 1) {
+        env->features[FEAT_1_EDX] &= ~CPUID_TSC;
+        env->features[FEAT_1_ECX] &= ~CPUID_EXT_TSC_DEADLINE_TIMER;
+        env->features[FEAT_8000_0001_EDX] &= ~CPUID_EXT2_RDTSCP;
+    }
+
     mce_init(cpu);
     qemu_init_vcpu(cs);
 
diff --git a/vl.c b/vl.c
index 7f8bd39..408094c 100644
--- a/vl.c
+++ b/vl.c
@@ -537,6 +537,19 @@ static QemuOptsList qemu_mem_opts = {
     },
 };
 
+static QemuOptsList qemu_slowtime_opts = {
+    .name = "slowtime",
+    .implied_opt_name = "divider",
+    .head = QTAILQ_HEAD_INITIALIZER(qemu_option_rom_opts.head),
+    .desc = {
+        {
+            .name = "divider",
+            .type = QEMU_OPT_NUMBER,
+        },
+        { /* end of list */ }
+    },
+};
+
 /**
  * Get machine options
  *
@@ -2979,6 +2992,7 @@ int main(int argc, char **argv, char **envp)
     qemu_add_opts(&qemu_msg_opts);
     qemu_add_opts(&qemu_name_opts);
     qemu_add_opts(&qemu_numa_opts);
+    qemu_add_opts(&qemu_slowtime_opts);
 
     runstate_init();
 
@@ -3961,6 +3975,16 @@ int main(int argc, char **argv, char **envp)
                     exit(1);
                 }
                 break;
+            case QEMU_OPTION_slowtime:
+                opts = qemu_opts_parse(qemu_find_opts("slowtime"), optarg, 0);
+                if (!opts) {
+                    exit(1);
+                }
+                slowtime_divider = qemu_opt_get_number(opts, "divider", 1);
+                if (slowtime_divider < 1) {
+                    exit(1);
+                }
+                break;
             default:
                 os_parse_cmd_args(popt->index, optarg);
             }
-- 
1.8.4.1