[PATCH 0/3] kvm: selftests: initial version of state save/restore test

[PATCH 0/3] kvm: selftests: initial version of state save/restore test

[Paolo Bonzini]

To be improved into a test for nested state save/restore

Paolo Bonzini (3):
  KVM: x86: ensures all MSRs can always be KVM_GET/SET_MSR'd
  kvm: selftests: ensure vcpu file is released
  kvm: selftests: add basic test for state save and restore

 arch/x86/kvm/hyperv.c                         |  27 +++-
 arch/x86/kvm/hyperv.h                         |   2 +-
 arch/x86/kvm/x86.c                            |  15 ++-
 tools/testing/selftests/kvm/Makefile          |   1 +
 tools/testing/selftests/kvm/include/x86.h     |   4 +
 tools/testing/selftests/kvm/lib/kvm_util.c    |  18 ++-
 .../selftests/kvm/lib/kvm_util_internal.h     |   1 +
 tools/testing/selftests/kvm/lib/x86.c         | 118 +++++++++++++++++
 tools/testing/selftests/kvm/state_test.c      | 123 ++++++++++++++++++
 9 files changed, 289 insertions(+), 20 deletions(-)
 create mode 100644 tools/testing/selftests/kvm/state_test.c

-- 
2.17.1

[PATCH 1/3] KVM: x86: ensures all MSRs can always be KVM_GET/SET_MSR'd

[Paolo Bonzini]

Some of the MSRs returned by GET_MSR_INDEX_LIST currently cannot be sent back
to KVM_GET_MSR and/or KVM_SET_MSR; either they can never be sent back, or you
they are only accepted under special conditions.  This makes the API a pain to
use.

To avoid this pain, this patch makes it so that the result of the get-list
ioctl can always be used for host-initiated get and set.  Since we don't have
a separate way to check for read-only MSRs, this means some Hyper-V MSRs are
ignored when written.  Arguably they should not even be in the result of
GET_MSR_INDEX_LIST, but I am leaving there in case userspace is using the
outcome of GET_MSR_INDEX_LIST to derive the support for the corresponding
Hyper-V feature.

Cc: stable@vger.kernel.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 arch/x86/kvm/hyperv.c | 27 ++++++++++++++++++++-------
 arch/x86/kvm/hyperv.h |  2 +-
 arch/x86/kvm/x86.c    | 15 +++++++++------
 3 files changed, 30 insertions(+), 14 deletions(-)

diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index af8caf965baa..01d209ab5481 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -235,7 +235,7 @@ static int synic_set_msr(struct kvm_vcpu_hv_synic *synic,
 	struct kvm_vcpu *vcpu = synic_to_vcpu(synic);
 	int ret;
 
-	if (!synic->active)
+	if (!synic->active && !host)
 		return 1;
 
 	trace_kvm_hv_synic_set_msr(vcpu->vcpu_id, msr, data, host);
@@ -295,11 +295,12 @@ static int synic_set_msr(struct kvm_vcpu_hv_synic *synic,
 	return ret;
 }
 
-static int synic_get_msr(struct kvm_vcpu_hv_synic *synic, u32 msr, u64 *pdata)
+static int synic_get_msr(struct kvm_vcpu_hv_synic *synic, u32 msr, u64 *pdata,
+			 bool host)
 {
 	int ret;
 
-	if (!synic->active)
+	if (!synic->active && !host)
 		return 1;
 
 	ret = 0;
@@ -1014,6 +1015,11 @@ static int kvm_hv_set_msr_pw(struct kvm_vcpu *vcpu, u32 msr, u64 data,
 	case HV_X64_MSR_TSC_EMULATION_STATUS:
 		hv->hv_tsc_emulation_status = data;
 		break;
+	case HV_X64_MSR_TIME_REF_COUNT:
+		/* read-only, but still ignore it if host-initiated */
+		if (!host)
+			return 1;
+		break;
 	default:
 		vcpu_unimpl(vcpu, "Hyper-V uhandled wrmsr: 0x%x data 0x%llx\n",
 			    msr, data);
@@ -1101,6 +1107,12 @@ static int kvm_hv_set_msr(struct kvm_vcpu *vcpu, u32 msr, u64 data, bool host)
 		return stimer_set_count(vcpu_to_stimer(vcpu, timer_index),
 					data, host);
 	}
+	case HV_X64_MSR_TSC_FREQUENCY:
+	case HV_X64_MSR_APIC_FREQUENCY:
+		/* read-only, but still ignore it if host-initiated */
+		if (!host)
+			return 1;
+		break;
 	default:
 		vcpu_unimpl(vcpu, "Hyper-V uhandled wrmsr: 0x%x data 0x%llx\n",
 			    msr, data);
@@ -1156,7 +1168,8 @@ static int kvm_hv_get_msr_pw(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata)
 	return 0;
 }
 
-static int kvm_hv_get_msr(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata)
+static int kvm_hv_get_msr(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata,
+			  bool host)
 {
 	u64 data = 0;
 	struct kvm_vcpu_hv *hv = &vcpu->arch.hyperv;
@@ -1183,7 +1196,7 @@ static int kvm_hv_get_msr(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata)
 	case HV_X64_MSR_SIMP:
 	case HV_X64_MSR_EOM:
 	case HV_X64_MSR_SINT0 ... HV_X64_MSR_SINT15:
-		return synic_get_msr(vcpu_to_synic(vcpu), msr, pdata);
+		return synic_get_msr(vcpu_to_synic(vcpu), msr, pdata, host);
 	case HV_X64_MSR_STIMER0_CONFIG:
 	case HV_X64_MSR_STIMER1_CONFIG:
 	case HV_X64_MSR_STIMER2_CONFIG:
@@ -1229,7 +1242,7 @@ int kvm_hv_set_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 data, bool host)
 		return kvm_hv_set_msr(vcpu, msr, data, host);
 }
 
-int kvm_hv_get_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata)
+int kvm_hv_get_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata, bool host)
 {
 	if (kvm_hv_msr_partition_wide(msr)) {
 		int r;
@@ -1239,7 +1252,7 @@ int kvm_hv_get_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata)
 		mutex_unlock(&vcpu->kvm->arch.hyperv.hv_lock);
 		return r;
 	} else
-		return kvm_hv_get_msr(vcpu, msr, pdata);
+		return kvm_hv_get_msr(vcpu, msr, pdata, host);
 }
 
 static __always_inline int get_sparse_bank_no(u64 valid_bank_mask, int bank_no)
diff --git a/arch/x86/kvm/hyperv.h b/arch/x86/kvm/hyperv.h
index 837465d69c6d..d6aa969e20f1 100644
--- a/arch/x86/kvm/hyperv.h
+++ b/arch/x86/kvm/hyperv.h
@@ -48,7 +48,7 @@ static inline struct kvm_vcpu *synic_to_vcpu(struct kvm_vcpu_hv_synic *synic)
 }
 
 int kvm_hv_set_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 data, bool host);
-int kvm_hv_get_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata);
+int kvm_hv_get_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata, bool host);
 
 bool kvm_hv_hypercall_enabled(struct kvm *kvm);
 int kvm_hv_hypercall(struct kvm_vcpu *vcpu);
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 153564db7980..f2876053e28b 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -2166,10 +2166,11 @@ static int set_msr_mce(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 		vcpu->arch.mcg_status = data;
 		break;
 	case MSR_IA32_MCG_CTL:
-		if (!(mcg_cap & MCG_CTL_P))
+		if (!(mcg_cap & MCG_CTL_P) &&
+		    (data || !msr_info->host_initiated))
 			return 1;
 		if (data != 0 && data != ~(u64)0)
-			return -1;
+			return 1;
 		vcpu->arch.mcg_ctl = data;
 		break;
 	default:
@@ -2557,7 +2558,7 @@ int kvm_get_msr(struct kvm_vcpu *vcpu, struct msr_data *msr)
 }
 EXPORT_SYMBOL_GPL(kvm_get_msr);
 
-static int get_msr_mce(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata)
+static int get_msr_mce(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata, bool host)
 {
 	u64 data;
 	u64 mcg_cap = vcpu->arch.mcg_cap;
@@ -2572,7 +2573,7 @@ static int get_msr_mce(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata)
 		data = vcpu->arch.mcg_cap;
 		break;
 	case MSR_IA32_MCG_CTL:
-		if (!(mcg_cap & MCG_CTL_P))
+		if (!(mcg_cap & MCG_CTL_P) && !host)
 			return 1;
 		data = vcpu->arch.mcg_ctl;
 		break;
@@ -2705,7 +2706,8 @@ int kvm_get_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 	case MSR_IA32_MCG_CTL:
 	case MSR_IA32_MCG_STATUS:
 	case MSR_IA32_MC0_CTL ... MSR_IA32_MCx_CTL(KVM_MAX_MCE_BANKS) - 1:
-		return get_msr_mce(vcpu, msr_info->index, &msr_info->data);
+		return get_msr_mce(vcpu, msr_info->index, &msr_info->data,
+				   msr_info->host_initiated);
 	case MSR_K7_CLK_CTL:
 		/*
 		 * Provide expected ramp-up count for K7. All other
@@ -2726,7 +2728,8 @@ int kvm_get_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 	case HV_X64_MSR_TSC_EMULATION_CONTROL:
 	case HV_X64_MSR_TSC_EMULATION_STATUS:
 		return kvm_hv_get_msr_common(vcpu,
-					     msr_info->index, &msr_info->data);
+					     msr_info->index, &msr_info->data,
+					     msr_info->host_initiated);
 		break;
 	case MSR_IA32_BBL_CR_CTL3:
 		/* This legacy MSR exists but isn't fully documented in current
-- 
2.17.1

[PATCH 2/3] kvm: selftests: ensure vcpu file is released

[Paolo Bonzini]

The selftests were not munmap-ing the kvm_run area from the vcpu file descriptor.
The result was that kvm_vcpu_release was not called and a reference was left in the
parent "struct kvm".  Ultimately this was visible in the upcoming state save/restore
test as an error when KVM attempted to create a duplicate debugfs entry.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 tools/testing/selftests/kvm/lib/kvm_util.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c
index 37e2a787d2fc..4930b1bdce62 100644
--- a/tools/testing/selftests/kvm/lib/kvm_util.c
+++ b/tools/testing/selftests/kvm/lib/kvm_util.c
@@ -238,8 +238,12 @@ struct vcpu *vcpu_find(struct kvm_vm *vm,
 static void vm_vcpu_rm(struct kvm_vm *vm, uint32_t vcpuid)
 {
 	struct vcpu *vcpu = vcpu_find(vm, vcpuid);
+	int ret;
 
-	int ret = close(vcpu->fd);
+	ret = munmap(vcpu->state, sizeof(*vcpu->state));
+	TEST_ASSERT(ret == 0, "munmap of VCPU fd failed, rc: %i "
+		"errno: %i", ret, errno);
+	close(vcpu->fd);
 	TEST_ASSERT(ret == 0, "Close of VCPU fd failed, rc: %i "
 		"errno: %i", ret, errno);
 
@@ -295,6 +299,10 @@ void kvm_vm_free(struct kvm_vm *vmp)
 	TEST_ASSERT(ret == 0, "Close of vm fd failed,\n"
 		"  vmp->fd: %i rc: %i errno: %i", vmp->fd, ret, errno);
 
+	close(vmp->kvm_fd);
+	TEST_ASSERT(ret == 0, "Close of /dev/kvm fd failed,\n"
+		"  vmp->kvm_fd: %i rc: %i errno: %i", vmp->kvm_fd, ret, errno);
+
 	/* Free the structure describing the VM. */
 	free(vmp);
 }
-- 
2.17.1

[PATCH 3/3] kvm: selftests: add basic test for state save and restore

[Paolo Bonzini]

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 tools/testing/selftests/kvm/Makefile          |   1 +
 tools/testing/selftests/kvm/include/x86.h     |   4 +
 tools/testing/selftests/kvm/lib/kvm_util.c    |   8 +-
 .../selftests/kvm/lib/kvm_util_internal.h     |   1 +
 tools/testing/selftests/kvm/lib/x86.c         | 118 +++++++++++++++++
 tools/testing/selftests/kvm/state_test.c      | 123 ++++++++++++++++++
 6 files changed, 250 insertions(+), 5 deletions(-)
 create mode 100644 tools/testing/selftests/kvm/state_test.c

diff --git a/tools/testing/selftests/kvm/Makefile b/tools/testing/selftests/kvm/Makefile
index 65bda4fb0ad6..dd0e5163f01f 100644
--- a/tools/testing/selftests/kvm/Makefile
+++ b/tools/testing/selftests/kvm/Makefile
@@ -10,6 +10,7 @@ TEST_GEN_PROGS_x86_64 = set_sregs_test
 TEST_GEN_PROGS_x86_64 += sync_regs_test
 TEST_GEN_PROGS_x86_64 += vmx_tsc_adjust_test
 TEST_GEN_PROGS_x86_64 += cr4_cpuid_sync_test
+TEST_GEN_PROGS_x86_64 += state_test
 
 TEST_GEN_PROGS += $(TEST_GEN_PROGS_$(UNAME_M))
 LIBKVM += $(LIBKVM_$(UNAME_M))
diff --git a/tools/testing/selftests/kvm/include/x86.h b/tools/testing/selftests/kvm/include/x86.h
index 4a5b2c4c1a0f..f73480e09770 100644
--- a/tools/testing/selftests/kvm/include/x86.h
+++ b/tools/testing/selftests/kvm/include/x86.h
@@ -303,6 +303,10 @@ static inline unsigned long get_xmm(int n)
 	return 0;
 }
 
+struct kvm_x86_state;
+struct kvm_x86_state *vcpu_save_state(struct kvm_vm *vm, uint32_t vcpuid);
+void vcpu_load_state(struct kvm_vm *vm, uint32_t vcpuid, struct kvm_x86_state *state);
+
 /*
  * Basic CPU control in CR0
  */
diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c
index 4930b1bdce62..3fe259cd9eba 100644
--- a/tools/testing/selftests/kvm/lib/kvm_util.c
+++ b/tools/testing/selftests/kvm/lib/kvm_util.c
@@ -90,17 +90,15 @@ struct kvm_vm *vm_create(enum vm_guest_mode mode, uint64_t phy_pages, int perm)
 	TEST_ASSERT(vm != NULL, "Insufficent Memory");
 
 	vm->mode = mode;
-	kvm_fd = open(KVM_DEV_PATH, perm);
-	if (kvm_fd < 0)
+	vm->kvm_fd = open(KVM_DEV_PATH, perm);
+	if (vm->kvm_fd < 0)
 		exit(KSFT_SKIP);
 
 	/* Create VM. */
-	vm->fd = ioctl(kvm_fd, KVM_CREATE_VM, NULL);
+	vm->fd = ioctl(vm->kvm_fd, KVM_CREATE_VM, NULL);
 	TEST_ASSERT(vm->fd >= 0, "KVM_CREATE_VM ioctl failed, "
 		"rc: %i errno: %i", vm->fd, errno);
 
-	close(kvm_fd);
-
 	/* Setup mode specific traits. */
 	switch (vm->mode) {
 	case VM_MODE_FLAT48PG:
diff --git a/tools/testing/selftests/kvm/lib/kvm_util_internal.h b/tools/testing/selftests/kvm/lib/kvm_util_internal.h
index a0bd1980c81c..6ff6e10fb302 100644
--- a/tools/testing/selftests/kvm/lib/kvm_util_internal.h
+++ b/tools/testing/selftests/kvm/lib/kvm_util_internal.h
@@ -43,6 +43,7 @@ struct vcpu {
 
 struct kvm_vm {
 	int mode;
+	int kvm_fd;
 	int fd;
 	unsigned int page_size;
 	unsigned int page_shift;
diff --git a/tools/testing/selftests/kvm/lib/x86.c b/tools/testing/selftests/kvm/lib/x86.c
index 2f17675f4275..0d2ea4815975 100644
--- a/tools/testing/selftests/kvm/lib/x86.c
+++ b/tools/testing/selftests/kvm/lib/x86.c
@@ -698,3 +698,115 @@ struct kvm_vm *vm_create_default(uint32_t vcpuid, void *guest_code)
 
 	return vm;
 }
+
+struct kvm_x86_state {
+	struct kvm_vcpu_events events;
+	struct kvm_mp_state mp_state;
+	struct kvm_regs regs;
+	struct kvm_xsave xsave;
+	struct kvm_xcrs xcrs;
+	struct kvm_sregs sregs;
+	struct kvm_debugregs debugregs;
+	struct kvm_msrs msrs;
+};
+
+static int kvm_get_num_msrs(struct kvm_vm *vm)
+{
+	struct kvm_msr_list nmsrs;
+	int r;
+
+	nmsrs.nmsrs = 0;
+	r = ioctl(vm->kvm_fd, KVM_GET_MSR_INDEX_LIST, &nmsrs);
+	TEST_ASSERT(r == -1 && errno == E2BIG, "Unexpected result from KVM_GET_MSR_INDEX_LIST probe, r: %i",
+		r);
+
+	return nmsrs.nmsrs;
+}
+
+struct kvm_x86_state *vcpu_save_state(struct kvm_vm *vm, uint32_t vcpuid)
+{
+	struct vcpu *vcpu = vcpu_find(vm, vcpuid);
+	struct kvm_msr_list *list;
+	struct kvm_x86_state *state;
+	int nmsrs, r, i;
+
+	nmsrs = kvm_get_num_msrs(vm);
+	list = malloc(sizeof(*list) + nmsrs * sizeof(list->indices[0]));
+	list->nmsrs = nmsrs;
+	r = ioctl(vm->kvm_fd, KVM_GET_MSR_INDEX_LIST, list);
+        TEST_ASSERT(r == 0, "Unexpected result from KVM_GET_MSR_INDEX_LIST, r: %i",
+                r);
+
+	state = malloc(sizeof(*state) + nmsrs * sizeof(state->msrs.entries[0]));
+	r = ioctl(vcpu->fd, KVM_GET_VCPU_EVENTS, &state->events);
+        TEST_ASSERT(r == 0, "Unexpected result from KVM_GET_VCPU_EVENTS, r: %i",
+                r);
+
+	r = ioctl(vcpu->fd, KVM_GET_MP_STATE, &state->mp_state);
+        TEST_ASSERT(r == 0, "Unexpected result from KVM_GET_MP_STATE, r: %i",
+                r);
+
+	r = ioctl(vcpu->fd, KVM_GET_REGS, &state->regs);
+        TEST_ASSERT(r == 0, "Unexpected result from KVM_GET_REGS, r: %i",
+                r);
+
+	r = ioctl(vcpu->fd, KVM_GET_XSAVE, &state->xsave);
+        TEST_ASSERT(r == 0, "Unexpected result from KVM_GET_XSAVE, r: %i",
+                r);
+
+	r = ioctl(vcpu->fd, KVM_GET_XCRS, &state->xcrs);
+        TEST_ASSERT(r == 0, "Unexpected result from KVM_GET_XCRS, r: %i",
+                r);
+
+	r = ioctl(vcpu->fd, KVM_GET_SREGS, &state->sregs);
+        TEST_ASSERT(r == 0, "Unexpected result from KVM_GET_SREGS, r: %i",
+                r);
+
+	state->msrs.nmsrs = nmsrs;
+	for (i = 0; i < nmsrs; i++)
+		state->msrs.entries[i].index = list->indices[i];
+	r = ioctl(vcpu->fd, KVM_GET_MSRS, &state->msrs);
+        TEST_ASSERT(r == nmsrs, "Unexpected result from KVM_GET_MSRS, r: %i (failed at %x)",
+                r, list->indices[r]);
+
+	r = ioctl(vcpu->fd, KVM_GET_DEBUGREGS, &state->debugregs);
+        TEST_ASSERT(r == 0, "Unexpected result from KVM_GET_DEBUGREGS, r: %i",
+                r);
+
+	free(list);
+	return state;
+}
+
+void vcpu_load_state(struct kvm_vm *vm, uint32_t vcpuid, struct kvm_x86_state *state)
+{
+	struct vcpu *vcpu = vcpu_find(vm, vcpuid);
+	int r;
+
+	r = ioctl(vcpu->fd, KVM_SET_XSAVE, &state->xsave);
+        TEST_ASSERT(r == 0, "Unexpected result from KVM_SET_XSAVE, r: %i",
+                r);
+
+	r = ioctl(vcpu->fd, KVM_SET_XCRS, &state->xcrs);
+        TEST_ASSERT(r == 0, "Unexpected result from KVM_SET_XCRS, r: %i",
+                r);
+
+	r = ioctl(vcpu->fd, KVM_SET_SREGS, &state->sregs);
+        TEST_ASSERT(r == 0, "Unexpected result from KVM_SET_SREGS, r: %i",
+                r);
+
+	r = ioctl(vcpu->fd, KVM_SET_MSRS, &state->msrs);
+        TEST_ASSERT(r == state->msrs.nmsrs, "Unexpected result from KVM_SET_MSRS, r: %i (failed at %x)",
+                r, state->msrs.entries[r].index);
+
+	r = ioctl(vcpu->fd, KVM_SET_VCPU_EVENTS, &state->events);
+        TEST_ASSERT(r == 0, "Unexpected result from KVM_SET_VCPU_EVENTS, r: %i",
+                r);
+
+	r = ioctl(vcpu->fd, KVM_SET_DEBUGREGS, &state->debugregs);
+        TEST_ASSERT(r == 0, "Unexpected result from KVM_SET_DEBUGREGS, r: %i",
+                r);
+
+	r = ioctl(vcpu->fd, KVM_SET_REGS, &state->regs);
+        TEST_ASSERT(r == 0, "Unexpected result from KVM_SET_REGS, r: %i",
+                r);
+}
diff --git a/tools/testing/selftests/kvm/state_test.c b/tools/testing/selftests/kvm/state_test.c
new file mode 100644
index 000000000000..1da3d173902c
--- /dev/null
+++ b/tools/testing/selftests/kvm/state_test.c
@@ -0,0 +1,123 @@
+/*
+ * KVM_SET_SREGS tests
+ *
+ * Copyright (C) 2018, Google LLC.
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2.
+ *
+ * This is a regression test for the bug fixed by the following commit:
+ * d3802286fa0f ("kvm: x86: Disallow illegal IA32_APIC_BASE MSR values")
+ *
+ * That bug allowed a user-mode program that called the KVM_SET_SREGS
+ * ioctl to put a VCPU's local APIC into an invalid state.
+ *
+ */
+#define _GNU_SOURCE /* for program_invocation_short_name */
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/ioctl.h>
+
+#include "test_util.h"
+
+#include "kvm_util.h"
+#include "x86.h"
+
+#define VCPU_ID                  5
+#define PORT_HOST_SYNC 0x1000
+
+static void __exit_to_l0(uint16_t port, uint64_t arg0, uint64_t arg1)
+{
+	__asm__ __volatile__("in %[port], %%al"
+			     :
+			     : [port]"d"(port), "D"(arg0), "S"(arg1)
+		     	     : "rax");
+}
+
+#define exit_to_l0(_port, _arg0, _arg1) \
+	__exit_to_l0(_port, (uint64_t) (_arg0), (uint64_t) (_arg1))
+
+#define GUEST_ASSERT(_condition) do { \
+	if (!(_condition)) \
+		exit_to_l0(PORT_ABORT, "Failed guest assert: " #_condition, 0);\
+} while (0)
+
+void guest_code(void)
+{
+	int i;
+	for (i = 0;; i++) {
+		exit_to_l0(PORT_HOST_SYNC, "hello", i);
+	}
+}
+
+void bad_code(void)
+{
+	for (;;)
+		exit_to_l0(PORT_HOST_SYNC, "goodbye", 0xdeadbeef);
+}
+
+int main(int argc, char *argv[])
+{
+	struct kvm_regs regs1, regs2;
+	struct kvm_vm *vm;
+	struct kvm_run *run;
+	struct kvm_x86_state *state;
+	ulong creation_rsp;
+	int rc;
+
+	/* Create VM */
+	vm = vm_create_default(VCPU_ID, guest_code);
+	run = vcpu_state(vm, VCPU_ID);
+
+        vcpu_regs_get(vm, VCPU_ID, &regs1);
+	creation_rsp = regs1.rsp;
+
+	_vcpu_run(vm, VCPU_ID);
+	TEST_ASSERT(run->exit_reason == KVM_EXIT_IO,
+		    "Unexpected exit reason: %u (%s),\n",
+		    run->exit_reason,
+		    exit_reason_str(run->exit_reason));
+
+	memset(&regs1, 0, sizeof(regs1));
+        vcpu_regs_get(vm, VCPU_ID, &regs1);
+	TEST_ASSERT(!strcmp((const char *)regs1.rdi, "hello") &&
+		    regs1.rsi == 0, "Unexpected register values after vmexit; rdi: %lx rsi: %lx",
+		    (ulong) regs1.rdi, (ulong) regs1.rsi);
+
+	state = vcpu_save_state(vm, VCPU_ID);
+	kvm_vm_free(vm);
+
+	/* Restore state in VM.  */
+	vm = vm_create_default(VCPU_ID, bad_code);
+        vcpu_regs_get(vm, VCPU_ID, &regs2);
+
+	/* stack_vaddr should be the same, or something is nondeterministic
+	 * in VM state creation.  Check just to be safe.
+	 */
+	TEST_ASSERT(creation_rsp == regs2.rsp,
+		    "Mismatching stack_vaddr - first %lx, second %lx",
+		    (ulong) creation_rsp, (ulong) regs2.rsp);
+
+	vcpu_load_state(vm, VCPU_ID, state);
+	memset(&regs2, 0, sizeof(regs2));
+        vcpu_regs_get(vm, VCPU_ID, &regs2);
+	TEST_ASSERT(!memcmp(&regs1, &regs2, sizeof(regs2)),
+		    "Unexpected register values after vcpu_load_state; rdi: %lx rsi: %lx",
+		    (ulong) regs2.rdi, (ulong) regs2.rsi);
+
+	_vcpu_run(vm, VCPU_ID);
+	TEST_ASSERT(run->exit_reason == KVM_EXIT_IO,
+		    "Unexpected exit reason: %u (%s),\n",
+		    run->exit_reason,
+		    exit_reason_str(run->exit_reason));
+
+        vcpu_regs_get(vm, VCPU_ID, &regs2);
+	TEST_ASSERT(!strcmp((const char *)regs2.rdi, "hello") &&
+		    regs2.rsi == 1, "Unexpected register values after second vmexit; rdi: %lx rsi: %lx",
+		    (ulong) regs2.rdi, (ulong) regs2.rsi);
+
+
+	kvm_vm_free(vm);
+	free(state);
+}
-- 
2.17.1