diff --git a/config-x86-common.mak b/config-x86-common.mak
index b8ca859..b541c1c 100644
--- a/config-x86-common.mak
+++ b/config-x86-common.mak
@@ -26,7 +26,8 @@ FLATLIBS = lib/libcflat.a $(libgcc)
 tests-common = $(TEST_DIR)/vmexit.flat $(TEST_DIR)/tsc.flat \
                $(TEST_DIR)/smptest.flat  $(TEST_DIR)/port80.flat \
                $(TEST_DIR)/realmode.flat $(TEST_DIR)/msr.flat \
-               $(TEST_DIR)/hypercall.flat $(TEST_DIR)/sieve.flat
+               $(TEST_DIR)/hypercall.flat $(TEST_DIR)/sieve.flat \
+               $(TEST_DIR)/kvmclock_test.flat
 
 tests_and_config = $(TEST_DIR)/*.flat $(TEST_DIR)/unittests.cfg
 
@@ -70,6 +71,9 @@ $(TEST_DIR)/rmap_chain.flat: $(cstart.o) $(TEST_DIR)/rmap_chain.o \
 
 $(TEST_DIR)/svm.flat: $(cstart.o) $(TEST_DIR)/vm.o
 
+$(TEST_DIR)/kvmclock_test.flat: $(cstart.o) $(TEST_DIR)/kvmclock.o \
+                                $(TEST_DIR)/kvmclock_test.o
+
 arch_clean:
 	$(RM) $(TEST_DIR)/*.o $(TEST_DIR)/*.flat \
 	$(TEST_DIR)/.*.d $(TEST_DIR)/lib/.*.d $(TEST_DIR)/lib/*.o
diff --git a/x86/README b/x86/README
index ab5a2ae..215fb2f 100644
--- a/x86/README
+++ b/x86/README
@@ -12,3 +12,4 @@ sieve: heavy memory access with no paging and with paging static and with paging
 smptest: run smp_id() on every cpu and compares return value to number
 tsc: write to tsc(0) and write to tsc(100000000000) and read it back
 vmexit: long loops for each: cpuid, vmcall, mov_from_cr8, mov_to_cr8, inl_pmtimer, ipi, ipi+halt
+kvmclock_test: test of wallclock, monotonic cycle and performance of kvmclock
diff --git a/x86/kvmclock_test.c b/x86/kvmclock_test.c
new file mode 100644
index 0000000..5b14ae2
--- /dev/null
+++ b/x86/kvmclock_test.c
@@ -0,0 +1,166 @@
+#include "libcflat.h"
+#include "smp.h"
+#include "atomic.h"
+#include "processor.h"
+#include "kvmclock.h"
+
+#define DEFAULT_TEST_LOOPS 100000000L
+#define DEFAULT_THRESHOLD  5L
+
+struct test_info {
+        struct spinlock lock;
+        long loops;               /* test loops */
+        u64 warps;                /* warp count */
+        u64 stalls;               /* stall count */
+        long long worst;          /* worst warp */
+        volatile cycle_t last;    /* last cycle seen by test */
+        atomic_t ncpus;           /* number of cpu in the test*/
+        int check;                /* check cycle ? */
+};
+
+struct test_info ti[4];
+
+static int wallclock_test(long sec, long threshold)
+{
+        long ksec, offset;
+        struct timespec ts;
+
+        printf("Wallclock test, threshold %ld\n", threshold);
+        kvm_get_wallclock(&ts);
+        ksec = ts.tv_sec;
+
+        offset = ksec - sec;
+        printf("Seconds get from host:     %ld\n", sec);
+        printf("Seconds get from kvmclock: %ld\n", ksec);
+        printf("Offset:                    %ld\n", offset);
+
+        if (offset > threshold || offset < -threshold) {
+                printf("offset too large!\n");
+                return 1;
+        }
+
+        return 0;
+}
+
+static void kvm_clock_test(void *data)
+{
+        struct test_info *hv_test_info = (struct test_info *)data;
+        long i, check = hv_test_info->check;
+
+        for (i = 0; i < hv_test_info->loops; i++){
+                cycle_t t0, t1;
+                long long delta;
+
+                if (check == 0) {
+                        kvm_clock_read();
+                        continue;
+                }
+
+                spin_lock(&hv_test_info->lock);
+                t1 = kvm_clock_read();
+                t0 = hv_test_info->last;
+                hv_test_info->last = kvm_clock_read();
+                spin_unlock(&hv_test_info->lock);
+
+                delta = t1 - t0;
+                if (delta < 0) {
+                        spin_lock(&hv_test_info->lock);
+                        ++hv_test_info->warps;
+                        if (delta < hv_test_info->worst){
+                                hv_test_info->worst = delta;
+                                printf("Worst warp %lld %\n", hv_test_info->worst);
+                        }
+                        spin_unlock(&hv_test_info->lock);
+                }
+                if (delta == 0)
+                        ++hv_test_info->stalls;
+
+                if (!((unsigned long)i & 31))
+                        asm volatile("rep; nop");
+        }
+
+        atomic_dec(&hv_test_info->ncpus);
+}
+
+static int cycle_test(int ncpus, long loops, int check, struct test_info *ti)
+{
+        int i;
+        unsigned long long begin, end;
+
+        begin = rdtsc();
+
+        atomic_set(&ti->ncpus, ncpus);
+        ti->loops = loops;
+        ti->check = check;
+        for (i = ncpus - 1; i >= 0; i--)
+                on_cpu_async(i, kvm_clock_test, (void *)ti);
+
+        /* Wait for the end of other vcpu */
+        while(atomic_read(&ti->ncpus))
+                ;
+
+        end = rdtsc();
+
+        printf("Total vcpus: %d\n", ncpus);
+        printf("Test  loops: %ld\n", ti->loops);
+        if (check == 1) {
+                printf("Total warps:  %lld\n", ti->warps);
+                printf("Total stalls: %lld\n", ti->stalls);
+                printf("Worst warp:   %lld\n", ti->worst);
+        } else
+                printf("TSC cycles:  %lld\n", end - begin);
+
+        return ti->warps ? 1 : 0;
+}
+
+int main(int ac, char **av)
+{
+        int ncpus = cpu_count();
+        int nerr = 0, i;
+        long loops = DEFAULT_TEST_LOOPS;
+        long sec = 0;
+        long threshold = DEFAULT_THRESHOLD;
+
+        if (ac > 1)
+                loops = atol(av[1]);
+        if (ac > 2)
+                sec = atol(av[2]);
+        if (ac > 3)
+                threshold = atol(av[3]);
+
+        smp_init();
+
+        if (ncpus > MAX_CPU)
+                ncpus = MAX_CPU;
+        for (i = 0; i < ncpus; ++i)
+                on_cpu(i, kvm_clock_init, (void *)0);
+
+        if (ac > 2)
+                nerr += wallclock_test(sec, threshold);
+
+        printf("Check the stability of raw cycle ...\n");
+        pvclock_set_flags(PVCLOCK_TSC_STABLE_BIT
+                          | PVCLOCK_RAW_CYCLE_BIT);
+        if (cycle_test(ncpus, loops, 1, &ti[0]))
+                printf("Raw cycle is not stable\n");
+        else
+                printf("Raw cycle is stable\n");
+
+        pvclock_set_flags(PVCLOCK_TSC_STABLE_BIT);
+        printf("Monotonic cycle test:\n");
+        nerr += cycle_test(ncpus, loops, 1, &ti[1]);
+
+        printf("Measure the performance of raw cycle ...\n");
+        pvclock_set_flags(PVCLOCK_TSC_STABLE_BIT
+                          | PVCLOCK_RAW_CYCLE_BIT);
+        cycle_test(ncpus, loops, 0, &ti[2]);
+
+        printf("Measure the performance of adjusted cycle ...\n");
+        pvclock_set_flags(PVCLOCK_TSC_STABLE_BIT);
+        cycle_test(ncpus, loops, 0, &ti[3]);
+
+        for (i = 0; i < ncpus; ++i)
+                on_cpu(i, kvm_clock_clear, (void *)0);
+
+        return nerr > 0 ? 1 : 0;
+}
diff --git a/x86/unittests.cfg b/x86/unittests.cfg
index 7796e41..228ac1d 100644
--- a/x86/unittests.cfg
+++ b/x86/unittests.cfg
@@ -63,3 +63,8 @@ extra_params = -enable-nesting -cpu qemu64,+svm
 file = svm.flat
 smp = 2
 extra_params = -cpu qemu64,-svm
+
+[kvmclock_test]
+file = kvmclock_test.flat
+smp = 2
+extra_params = --append "10000000 `date +%s`"
