diff --git a/x86/Makefile.common b/x86/Makefile.common
index 7bb6b50..ca97a8e 100644
--- a/x86/Makefile.common
+++ b/x86/Makefile.common
@@ -49,6 +49,7 @@ tests-common = $(TEST_DIR)/vmexit.flat $(TEST_DIR)/tsc.flat \
                $(TEST_DIR)/tsc_adjust.flat $(TEST_DIR)/asyncpf.flat \
                $(TEST_DIR)/init.flat $(TEST_DIR)/smap.flat \
                $(TEST_DIR)/hyperv_synic.flat $(TEST_DIR)/hyperv_stimer.flat \
+               $(TEST_DIR)/hyperv_connections.flat \
 
 ifdef API
 tests-api = api/api-sample api/dirty-log api/dirty-log-perf
@@ -71,6 +72,8 @@ $(TEST_DIR)/hyperv_synic.elf: $(TEST_DIR)/hyperv.o
 
 $(TEST_DIR)/hyperv_stimer.elf: $(TEST_DIR)/hyperv.o
 
+$(TEST_DIR)/hyperv_connections.elf: $(TEST_DIR)/hyperv.o
+
 arch_clean:
 	$(RM) $(TEST_DIR)/*.o $(TEST_DIR)/*.flat $(TEST_DIR)/*.elf \
 	$(TEST_DIR)/.*.d lib/x86/.*.d \
diff --git a/x86/hyperv_connections.c b/x86/hyperv_connections.c
new file mode 100644
index 0000000..b061048
--- /dev/null
+++ b/x86/hyperv_connections.c
@@ -0,0 +1,336 @@
+#include "libcflat.h"
+#include "vm.h"
+#include "smp.h"
+#include "isr.h"
+#include "atomic.h"
+#include "hyperv.h"
+#include "bitops.h"
+
+#define MAX_CPUS 64
+
+#define MSG_VEC 0xb0
+#define EVT_VEC 0xb1
+#define MSG_SINT 0x8
+#define EVT_SINT 0x9
+#define MSG_CONN_BASE 0x10
+#define EVT_CONN_BASE 0x20
+#define MSG_TYPE 0x12345678
+
+#define WAIT_CYCLES 10000000
+
+static atomic_t ncpus_done;
+
+struct hv_vcpu {
+	struct hv_message_page *msg_page;
+	struct hv_event_flags_page *evt_page;
+	struct hv_input_post_message *post_msg;
+	u8 msg_conn;
+	u8 evt_conn;
+	u64 hvcall_status;
+	atomic_t sint_received;
+};
+
+static struct hv_vcpu hv_vcpus[MAX_CPUS];
+
+static void sint_isr(isr_regs_t *regs)
+{
+	atomic_inc(&hv_vcpus[smp_id()].sint_received);
+}
+
+static void *hypercall_page;
+
+static void setup_hypercall(void)
+{
+	u64 guestid = (0x8f00ull << 48);
+
+	hypercall_page = alloc_page();
+	if (!hypercall_page)
+		report_abort("failed to allocate hypercall page");
+	memset(hypercall_page, 0, PAGE_SIZE);
+
+	wrmsr(HV_X64_MSR_GUEST_OS_ID, guestid);
+
+	wrmsr(HV_X64_MSR_HYPERCALL,
+	      (u64)virt_to_phys(hypercall_page) | HV_X64_MSR_HYPERCALL_ENABLE);
+}
+
+static void teardown_hypercall(void)
+{
+	wrmsr(HV_X64_MSR_HYPERCALL, 0);
+	wrmsr(HV_X64_MSR_GUEST_OS_ID, 0);
+	free_page(hypercall_page);
+}
+
+static u64 do_hypercall(u16 code, u64 arg, bool fast)
+{
+	u64 ret;
+	u64 ctl = code;
+	if (fast)
+		ctl |= HV_HYPERCALL_FAST;
+
+	asm volatile ("call *%[hcall_page]"
+#ifdef __x86_64__
+		      "\n mov $0,%%r8"
+		      : "=a"(ret)
+		      : "c"(ctl), "d"(arg),
+#else
+		      : "=A"(ret)
+		      : "A"(ctl),
+			"b" ((u32)(arg >> 32)), "c" ((u32)arg),
+			"D"(0), "S"(0),
+#endif
+		      [hcall_page] "m" (hypercall_page)
+#ifdef __x86_64__
+		      : "r8"
+#endif
+		     );
+
+	return ret;
+}
+
+static void setup_cpu(void *ctx)
+{
+	int vcpu;
+	struct hv_vcpu *hv;
+
+	write_cr3((ulong)ctx);
+	irq_enable();
+
+	vcpu = smp_id();
+	hv = &hv_vcpus[vcpu];
+
+	hv->msg_page = alloc_page();
+	hv->evt_page = alloc_page();
+	hv->post_msg = alloc_page();
+	if (!hv->msg_page || !hv->evt_page || !hv->post_msg)
+		report_abort("failed to allocate synic pages for vcpu");
+	memset(hv->msg_page, 0, sizeof(*hv->msg_page));
+	memset(hv->evt_page, 0, sizeof(*hv->evt_page));
+	memset(hv->post_msg, 0, sizeof(*hv->post_msg));
+	hv->msg_conn = MSG_CONN_BASE + vcpu;
+	hv->evt_conn = EVT_CONN_BASE + vcpu;
+
+	wrmsr(HV_X64_MSR_SIMP,
+	      (u64)virt_to_phys(hv->msg_page) | HV_SYNIC_SIMP_ENABLE);
+	wrmsr(HV_X64_MSR_SIEFP,
+	      (u64)virt_to_phys(hv->evt_page) | HV_SYNIC_SIEFP_ENABLE);
+	wrmsr(HV_X64_MSR_SCONTROL, HV_SYNIC_CONTROL_ENABLE);
+
+	msg_conn_create(MSG_SINT, MSG_VEC, hv->msg_conn);
+	evt_conn_create(EVT_SINT, EVT_VEC, hv->evt_conn);
+
+	hv->post_msg->connectionid = hv->msg_conn;
+	hv->post_msg->message_type = MSG_TYPE;
+	hv->post_msg->payload_size = 8;
+	hv->post_msg->payload[0] = (u64)vcpu << 16;
+}
+
+static void teardown_cpu(void *ctx)
+{
+	int vcpu = smp_id();
+	struct hv_vcpu *hv = &hv_vcpus[vcpu];
+
+	evt_conn_destroy(EVT_SINT, hv->evt_conn);
+	msg_conn_destroy(MSG_SINT, hv->msg_conn);
+
+	wrmsr(HV_X64_MSR_SCONTROL, 0);
+	wrmsr(HV_X64_MSR_SIEFP, 0);
+	wrmsr(HV_X64_MSR_SIMP, 0);
+
+	free_page(hv->post_msg);
+	free_page(hv->evt_page);
+	free_page(hv->msg_page);
+}
+
+static void do_msg(void *ctx)
+{
+	int vcpu = (ulong)ctx;
+	struct hv_vcpu *hv = &hv_vcpus[vcpu];
+	struct hv_input_post_message *msg = hv->post_msg;
+
+	msg->payload[0]++;
+	atomic_set(&hv->sint_received, 0);
+	hv->hvcall_status = do_hypercall(HVCALL_POST_MESSAGE,
+					 virt_to_phys(msg), 0);
+	atomic_inc(&ncpus_done);
+}
+
+static void clear_msg(void *ctx)
+{
+	/* should only be done on the current vcpu */
+	int vcpu = smp_id();
+	struct hv_vcpu *hv = &hv_vcpus[vcpu];
+	struct hv_message *msg = &hv->msg_page->sint_message[MSG_SINT];
+
+	atomic_set(&hv->sint_received, 0);
+	msg->header.message_type = 0;
+	barrier();
+	wrmsr(HV_X64_MSR_EOM, 0);
+	atomic_inc(&ncpus_done);
+}
+
+static bool msg_ok(int vcpu)
+{
+	struct hv_vcpu *hv = &hv_vcpus[vcpu];
+	struct hv_input_post_message *post_msg = hv->post_msg;
+	struct hv_message *msg = &hv->msg_page->sint_message[MSG_SINT];
+
+	return msg->header.message_type == post_msg->message_type &&
+		msg->header.payload_size == post_msg->payload_size &&
+		msg->header.message_flags.msg_pending == 0 &&
+		msg->u.payload[0] == post_msg->payload[0] &&
+		hv->hvcall_status == 0 &&
+		atomic_read(&hv->sint_received) == 1;
+}
+
+static bool msg_busy(int vcpu)
+{
+	struct hv_vcpu *hv = &hv_vcpus[vcpu];
+	struct hv_input_post_message *post_msg = hv->post_msg;
+	struct hv_message *msg = &hv->msg_page->sint_message[MSG_SINT];
+
+	return msg->header.message_type == post_msg->message_type &&
+		msg->header.payload_size == post_msg->payload_size &&
+		msg->header.message_flags.msg_pending == 1 &&
+		msg->u.payload[0] == post_msg->payload[0] - 1 &&
+		hv->hvcall_status == 0 &&
+		atomic_read(&hv->sint_received) == 0;
+}
+
+static void do_evt(void *ctx)
+{
+	int vcpu = (ulong)ctx;
+	struct hv_vcpu *hv = &hv_vcpus[vcpu];
+
+	atomic_set(&hv->sint_received, 0);
+	hv->hvcall_status = do_hypercall(HVCALL_SIGNAL_EVENT,
+					 hv->evt_conn, 1);
+	atomic_inc(&ncpus_done);
+}
+
+static void clear_evt(void *ctx)
+{
+	/* should only be done on the current vcpu */
+	int vcpu = smp_id();
+	struct hv_vcpu *hv = &hv_vcpus[vcpu];
+	ulong *flags = hv->evt_page->slot[EVT_SINT].flags;
+
+	atomic_set(&hv->sint_received, 0);
+	flags[BIT_WORD(hv->evt_conn)] &= ~BIT_MASK(hv->evt_conn);
+	barrier();
+	atomic_inc(&ncpus_done);
+}
+
+static bool evt_ok(int vcpu)
+{
+	struct hv_vcpu *hv = &hv_vcpus[vcpu];
+	ulong *flags = hv->evt_page->slot[EVT_SINT].flags;
+
+	return flags[BIT_WORD(hv->evt_conn)] == BIT_MASK(hv->evt_conn) &&
+		hv->hvcall_status == 0 &&
+		atomic_read(&hv->sint_received) == 1;
+}
+
+static bool evt_busy(int vcpu)
+{
+	struct hv_vcpu *hv = &hv_vcpus[vcpu];
+	ulong *flags = hv->evt_page->slot[EVT_SINT].flags;
+
+	return flags[BIT_WORD(hv->evt_conn)] == BIT_MASK(hv->evt_conn) &&
+		hv->hvcall_status == 0 &&
+		atomic_read(&hv->sint_received) == 0;
+}
+
+static int run_test(int ncpus, int dst_add, ulong wait_cycles,
+		    void (*func)(void *), bool (*is_ok)(int))
+{
+	int i, ret = 0;
+
+	atomic_set(&ncpus_done, 0);
+	for (i = 0; i < ncpus; i++) {
+		ulong dst = (i + dst_add) % ncpus;
+		on_cpu_async(i, func, (void *)dst);
+	}
+	while (atomic_read(&ncpus_done) != ncpus)
+		pause();
+
+	while (wait_cycles--)
+		pause();
+
+	if (is_ok)
+		for (i = 0; i < ncpus; i++)
+			ret += is_ok(i);
+	return ret;
+}
+
+#define HV_STATUS_INVALID_HYPERCALL_CODE        2
+
+int main(int ac, char **av)
+{
+	int ncpus, ncpus_ok, i;
+
+	if (!synic_supported()) {
+		report_skip("Hyper-V SynIC is not supported");
+		goto summary;
+	}
+
+	setup_vm();
+	smp_init();
+	ncpus = cpu_count();
+	if (ncpus > MAX_CPUS)
+		report_abort("# cpus: %d > %d", ncpus, MAX_CPUS);
+
+	handle_irq(MSG_VEC, sint_isr);
+	handle_irq(EVT_VEC, sint_isr);
+
+	setup_hypercall();
+
+	if (do_hypercall(HVCALL_SIGNAL_EVENT, 0x1234, 1) ==
+	    HV_STATUS_INVALID_HYPERCALL_CODE) {
+		report_skip("Hyper-V SynIC connections are not supported");
+		goto summary;
+	}
+
+	for (i = 0; i < ncpus; i++)
+		on_cpu(i, setup_cpu, (void *)read_cr3());
+
+	ncpus_ok = run_test(ncpus, 0, WAIT_CYCLES, do_msg, msg_ok);
+	report("send message to self: %d/%d",
+	       ncpus_ok == ncpus, ncpus_ok, ncpus);
+
+	run_test(ncpus, 0, 0, clear_msg, NULL);
+
+	ncpus_ok = run_test(ncpus, 1, WAIT_CYCLES, do_msg, msg_ok);
+	report("send message to another cpu: %d/%d",
+	       ncpus_ok == ncpus, ncpus_ok, ncpus);
+
+	ncpus_ok = run_test(ncpus, 1, WAIT_CYCLES, do_msg, msg_busy);
+	report("send message to busy slot: %d/%d",
+	       ncpus_ok == ncpus, ncpus_ok, ncpus);
+
+	ncpus_ok = run_test(ncpus, 0, WAIT_CYCLES, clear_msg, msg_ok);
+	report("receive pending message: %d/%d",
+	       ncpus_ok == ncpus, ncpus_ok, ncpus);
+
+	ncpus_ok = run_test(ncpus, 0, WAIT_CYCLES, do_evt, evt_ok);
+	report("signal event on self: %d/%d",
+	       ncpus_ok == ncpus, ncpus_ok, ncpus);
+
+	run_test(ncpus, 0, 0, clear_evt, NULL);
+
+	ncpus_ok = run_test(ncpus, 1, WAIT_CYCLES, do_evt, evt_ok);
+	report("signal event on another cpu: %d/%d",
+	       ncpus_ok == ncpus, ncpus_ok, ncpus);
+
+	ncpus_ok = run_test(ncpus, 1, WAIT_CYCLES, do_evt, evt_busy);
+	report("signal event already set: %d/%d",
+	       ncpus_ok == ncpus, ncpus_ok, ncpus);
+
+	for (i = 0; i < ncpus; i++)
+		on_cpu(i, teardown_cpu, NULL);
+
+	teardown_hypercall();
+
+summary:
+	return report_summary();
+}
diff --git a/x86/unittests.cfg b/x86/unittests.cfg
index 42f1ad4..3f3ad2a 100644
--- a/x86/unittests.cfg
+++ b/x86/unittests.cfg
@@ -504,6 +504,12 @@ smp = 2
 extra_params = -cpu kvm64,hv_synic -device hyperv-testdev
 groups = hyperv
 
+[hyperv_connections]
+file = hyperv_connections.flat
+smp = 2
+extra_params = -cpu kvm64,hv_synic -device hyperv-testdev
+groups = hyperv
+
 [hyperv_stimer]
 file = hyperv_stimer.flat
 smp = 2
