[v7,7/8] tests: Add unit tests for the VM Generation ID feature

Commit Message

[e-mail] Feb. 16, 2017, 6:18 a.m. UTC

From: Ben Warren <[e-mail]>

The following tests are implemented:
* test that a GUID passed in by command line is propagated to the guest.
  Read the GUID both from guest memory and from the monitor
* test that the "auto" argument to the GUID generates a valid GUID, as
  seen by the guest.

  This patch is loosely based on a previous patch from:
  Gal Hammer <[e-mail]>  and Igor Mammedov <[e-mail]>

Signed-off-by: Ben Warren <[e-mail]>
---
 tests/Makefile.include |   2 +
 tests/vmgenid-test.c   | 174 +++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 176 insertions(+)
 create mode 100644 tests/vmgenid-test.c

Comments

Igor Mammedov Feb. 16, 2017, 10:36 a.m. UTC | #1

On Wed, 15 Feb 2017 22:18:17 -0800
[e-mail] wrote:

> From: Ben Warren <[e-mail]>
> 
> The following tests are implemented:
> * test that a GUID passed in by command line is propagated to the guest.
>   Read the GUID both from guest memory and from the monitor
> * test that the "auto" argument to the GUID generates a valid GUID, as
>   seen by the guest.
> 
>   This patch is loosely based on a previous patch from:
>   Gal Hammer <[e-mail]>  and Igor Mammedov <[e-mail]>
> 
> Signed-off-by: Ben Warren <[e-mail]>
> ---
>  tests/Makefile.include |   2 +
>  tests/vmgenid-test.c   | 174 +++++++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 176 insertions(+)
>  create mode 100644 tests/vmgenid-test.c
> 
> diff --git a/tests/Makefile.include b/tests/Makefile.include
> index 143507e..8d36341 100644
> --- a/tests/Makefile.include
> +++ b/tests/Makefile.include
> @@ -241,6 +241,7 @@ check-qtest-i386-y += tests/usb-hcd-xhci-test$(EXESUF)
>  gcov-files-i386-y += hw/usb/hcd-xhci.c
>  check-qtest-i386-y += tests/pc-cpu-test$(EXESUF)
>  check-qtest-i386-y += tests/q35-test$(EXESUF)
> +check-qtest-i386-y += tests/vmgenid-test$(EXESUF)
>  gcov-files-i386-y += hw/pci-host/q35.c
>  check-qtest-i386-$(CONFIG_VHOST_NET_TEST_i386) += tests/vhost-user-test$(EXESUF)
>  ifeq ($(CONFIG_VHOST_NET_TEST_i386),)
> @@ -726,6 +727,7 @@ tests/ivshmem-test$(EXESUF): tests/ivshmem-test.o contrib/ivshmem-server/ivshmem
>  tests/vhost-user-bridge$(EXESUF): tests/vhost-user-bridge.o contrib/libvhost-user/libvhost-user.o $(test-util-obj-y)
>  tests/test-uuid$(EXESUF): tests/test-uuid.o $(test-util-obj-y)
>  tests/test-arm-mptimer$(EXESUF): tests/test-arm-mptimer.o
> +tests/vmgenid-test$(EXESUF): tests/vmgenid-test.o tests/acpi-utils.o
>  
>  tests/migration/stress$(EXESUF): tests/migration/stress.o
>  	$(call quiet-command, $(LINKPROG) -static -O3 $(PTHREAD_LIB) -o $@ $< ,"LINK","$(TARGET_DIR)$@")
> diff --git a/tests/vmgenid-test.c b/tests/vmgenid-test.c
> new file mode 100644
> index 0000000..1741455
> --- /dev/null
> +++ b/tests/vmgenid-test.c
> @@ -0,0 +1,174 @@
> +/*
> + * QTest testcase for VM Generation ID
> + *
> + * Copyright (c) 2016 Red Hat, Inc.
> + * Copyright (c) 2017 Skyport Systems
> + *
> + * This work is licensed under the terms of the GNU GPL, version 2 or later.
> + * See the COPYING file in the top-level directory.
> + */
> +
> +#include <glib.h>
> +#include <string.h>
> +#include <unistd.h>
> +#include "qemu/osdep.h"
> +#include "qemu/bitmap.h"
> +#include "qemu/uuid.h"
> +#include "hw/acpi/acpi-defs.h"
> +#include "acpi-utils.h"
> +#include "libqtest.h"
> +
> +#define VGID_GUID "324e6eaf-d1d1-4bf6-bf41-b9bb6c91fb87"
> +#define VMGENID_GUID_OFFSET      40   /* allow space for
> +                                       * OVMF SDT Header Probe Supressor
> +                                       */
> +
> +typedef struct {
> +    AcpiTableHeader header;
> +    gchar name_op;
> +    gchar vgia[4];
> +    gchar val_op;
> +    uint32_t vgia_val;
> +} QEMU_PACKED VgidTable;
> +
> +static uint32_t acpi_find_vgia(void)
> +{
> +    uint32_t off;
> +    AcpiRsdpDescriptor rsdp_table;
> +    uint32_t rsdt;
> +    AcpiRsdtDescriptorRev1 rsdt_table;
> +    int tables_nr;
> +    uint32_t *tables;
> +    AcpiTableHeader ssdt_table;
> +    VgidTable vgid_table;
> +    int i;
> +
> +    off = acpi_find_rsdp_address();
> +    g_assert_cmphex(off, <, 0x100000);
something's off here,
it fails for me for me with:

QTEST_QEMU_BINARY=x86_64-softmmu/qemu-system-x86_64 tests/vmgenid-test
/x86_64/vmgenid/vmgenid: **
ERROR:/home/imammedo/builds/qemu/tests/vmgenid-test.c:47:acpi_find_vgia: assertion failed (off < 0x100000): (0x00100000 < 0x00100000)

> +
> +    acpi_parse_rsdp_table(off, &rsdp_table);
> +
> +    rsdt = rsdp_table.rsdt_physical_address;
> +    /* read the header */
> +    ACPI_READ_TABLE_HEADER(&rsdt_table, rsdt);
> +    ACPI_ASSERT_CMP(rsdt_table.signature, "RSDT");
> +
> +    /* compute the table entries in rsdt */
> +    tables_nr = (rsdt_table.length - sizeof(AcpiRsdtDescriptorRev1)) /
> +                sizeof(uint32_t);
> +    g_assert_cmpint(tables_nr, >, 0);
> +
> +    /* get the addresses of the tables pointed by rsdt */
> +    tables = g_new0(uint32_t, tables_nr);
> +    ACPI_READ_ARRAY_PTR(tables, tables_nr, rsdt);
> +
> +    for (i = 0; i < tables_nr; i++) {
> +        ACPI_READ_TABLE_HEADER(&ssdt_table, tables[i]);
> +        if (!strncmp((char *)ssdt_table.oem_table_id, "VMGENID", 7)) {
> +            /* the first entry in the table should be VGIA
> +             * That's all we need
> +             */
> +            ACPI_READ_FIELD(vgid_table.name_op, tables[i]);
> +            g_assert(vgid_table.name_op == 0x08);  /* name */
> +            ACPI_READ_ARRAY(vgid_table.vgia, tables[i]);
> +            g_assert(memcmp(vgid_table.vgia, "VGIA", 4) == 0);
> +            ACPI_READ_FIELD(vgid_table.val_op, tables[i]);
> +            g_assert(vgid_table.val_op == 0x0C);  /* dword */
> +            ACPI_READ_FIELD(vgid_table.vgia_val, tables[i]);
> +            /* The GUID is written at a fixed offset into the fw_cfg file
> +             * in order to implement the "OVMF SDT Header probe suppressor"
> +             * see docs/specs/vmgenid.txt for more details
> +             */
> +            return vgid_table.vgia_val + VMGENID_GUID_OFFSET;
> +        }
> +    }
> +    return 0;
> +}
> +
> +static void read_guid_from_memory(QemuUUID *guid)
> +{
> +    uint32_t vmgenid_addr;
> +    int i;
> +
> +    vmgenid_addr = acpi_find_vgia();
> +    g_assert(vmgenid_addr);
> +
> +    /* Read the GUID directly from guest memory */
> +    for (i = 0; i < 16; i++) {
> +        guid->data[i] = readb(vmgenid_addr + i);
> +    }
> +    /* The GUID is in little-endian format in the guest, while QEMU
> +     * uses big-endian.  Swap after reading.
> +     */
> +    qemu_uuid_bswap(guid);
> +}
> +
> +static void read_guid_from_monitor(QemuUUID *guid)
> +{
> +    QDict *rsp, *rsp_ret;
> +    const char *guid_str;
> +
> +    rsp = qmp("{ 'execute': 'query-vm-generation-id' }");
> +    if (qdict_haskey(rsp, "return")) {
> +        rsp_ret = qdict_get_qdict(rsp, "return");
> +        g_assert(qdict_haskey(rsp_ret, "guid"));
> +        guid_str = qdict_get_str(rsp_ret, "guid");
> +        g_assert(qemu_uuid_parse(guid_str, guid) == 0);
> +    }
> +    QDECREF(rsp);
> +}
> +
> +static void vmgenid_test(void)
> +{
> +    QemuUUID expected, measured;
> +    gchar *cmd;
> +
> +    g_assert(qemu_uuid_parse(VGID_GUID, &expected) == 0);
> +
> +    cmd = g_strdup_printf("-machine accel=tcg -device vmgenid,id=testvgid,"
> +                          "guid=%s", VGID_GUID);
> +    qtest_start(cmd);
> +
> +    /* Read the GUID from accessing guest memory */
> +    read_guid_from_memory(&measured);
> +    g_assert(memcmp(measured.data, expected.data, sizeof(measured.data)) == 0);
> +
> +    /* Read the GUID via the monitor */
> +    read_guid_from_monitor(&measured);
> +    g_assert(memcmp(measured.data, expected.data, sizeof(measured.data)) == 0);
> +
> +    qtest_quit(global_qtest);
> +    g_free(cmd);
> +}
> +
> +static void vmgenid_set_guid_auto_test(void)
> +{
> +    const char *cmd;
> +    QemuUUID measured;
> +
> +    cmd = "-machine accel=tcg -device vmgenid,id=testvgid," "guid=auto";
> +    qtest_start(cmd);
> +
> +    read_guid_from_memory(&measured);
> +
> +    /* Just check that the GUID is non-null */
> +    g_assert(!qemu_uuid_is_null(&measured));
> +
> +    qtest_quit(global_qtest);
> +}
> +
> +int main(int argc, char **argv)
> +{
> +    int ret;
> +
> +    g_test_init(&argc, &argv, NULL);
> +
> +    qtest_add_func("/vmgenid/vmgenid", vmgenid_test);
> +    qtest_add_func("/vmgenid/vmgenid/set-guid-auto",
> +                   vmgenid_set_guid_auto_test);
> +    ret = g_test_run();
> +
> +    qtest_end();
> +
> +    return ret;
> +}

[e-mail] Feb. 16, 2017, 5:05 p.m. UTC | #2

> On Feb 16, 2017, at 2:36 AM, Igor Mammedov <[e-mail]> wrote:
> 
> On Wed, 15 Feb 2017 22:18:17 -0800
> [e-mail] <mailto:[e-mail]> wrote:
> 
>> From: Ben Warren <[e-mail]>
>> 
>> The following tests are implemented:
>> * test that a GUID passed in by command line is propagated to the guest.
>>  Read the GUID both from guest memory and from the monitor
>> * test that the "auto" argument to the GUID generates a valid GUID, as
>>  seen by the guest.
>> 
>>  This patch is loosely based on a previous patch from:
>>  Gal Hammer <[e-mail]>  and Igor Mammedov <[e-mail]>
>> 
>> Signed-off-by: Ben Warren <[e-mail]>
>> ---
>> tests/Makefile.include |   2 +
>> tests/vmgenid-test.c   | 174 +++++++++++++++++++++++++++++++++++++++++++++++++
>> 2 files changed, 176 insertions(+)
>> create mode 100644 tests/vmgenid-test.c
>> 
>> diff --git a/tests/Makefile.include b/tests/Makefile.include
>> index 143507e..8d36341 100644
>> --- a/tests/Makefile.include
>> +++ b/tests/Makefile.include
>> @@ -241,6 +241,7 @@ check-qtest-i386-y += tests/usb-hcd-xhci-test$(EXESUF)
>> gcov-files-i386-y += hw/usb/hcd-xhci.c
>> check-qtest-i386-y += tests/pc-cpu-test$(EXESUF)
>> check-qtest-i386-y += tests/q35-test$(EXESUF)
>> +check-qtest-i386-y += tests/vmgenid-test$(EXESUF)
>> gcov-files-i386-y += hw/pci-host/q35.c
>> check-qtest-i386-$(CONFIG_VHOST_NET_TEST_i386) += tests/vhost-user-test$(EXESUF)
>> ifeq ($(CONFIG_VHOST_NET_TEST_i386),)
>> @@ -726,6 +727,7 @@ tests/ivshmem-test$(EXESUF): tests/ivshmem-test.o contrib/ivshmem-server/ivshmem
>> tests/vhost-user-bridge$(EXESUF): tests/vhost-user-bridge.o contrib/libvhost-user/libvhost-user.o $(test-util-obj-y)
>> tests/test-uuid$(EXESUF): tests/test-uuid.o $(test-util-obj-y)
>> tests/test-arm-mptimer$(EXESUF): tests/test-arm-mptimer.o
>> +tests/vmgenid-test$(EXESUF): tests/vmgenid-test.o tests/acpi-utils.o
>> 
>> tests/migration/stress$(EXESUF): tests/migration/stress.o
>> 	$(call quiet-command, $(LINKPROG) -static -O3 $(PTHREAD_LIB) -o $@ $< ,"LINK","$(TARGET_DIR)$@")
>> diff --git a/tests/vmgenid-test.c b/tests/vmgenid-test.c
>> new file mode 100644
>> index 0000000..1741455
>> --- /dev/null
>> +++ b/tests/vmgenid-test.c
>> @@ -0,0 +1,174 @@
>> +/*
>> + * QTest testcase for VM Generation ID
>> + *
>> + * Copyright (c) 2016 Red Hat, Inc.
>> + * Copyright (c) 2017 Skyport Systems
>> + *
>> + * This work is licensed under the terms of the GNU GPL, version 2 or later.
>> + * See the COPYING file in the top-level directory.
>> + */
>> +
>> +#include <glib.h>
>> +#include <string.h>
>> +#include <unistd.h>
>> +#include "qemu/osdep.h"
>> +#include "qemu/bitmap.h"
>> +#include "qemu/uuid.h"
>> +#include "hw/acpi/acpi-defs.h"
>> +#include "acpi-utils.h"
>> +#include "libqtest.h"
>> +
>> +#define VGID_GUID "324e6eaf-d1d1-4bf6-bf41-b9bb6c91fb87"
>> +#define VMGENID_GUID_OFFSET      40   /* allow space for
>> +                                       * OVMF SDT Header Probe Supressor
>> +                                       */
>> +
>> +typedef struct {
>> +    AcpiTableHeader header;
>> +    gchar name_op;
>> +    gchar vgia[4];
>> +    gchar val_op;
>> +    uint32_t vgia_val;
>> +} QEMU_PACKED VgidTable;
>> +
>> +static uint32_t acpi_find_vgia(void)
>> +{
>> +    uint32_t off;
>> +    AcpiRsdpDescriptor rsdp_table;
>> +    uint32_t rsdt;
>> +    AcpiRsdtDescriptorRev1 rsdt_table;
>> +    int tables_nr;
>> +    uint32_t *tables;
>> +    AcpiTableHeader ssdt_table;
>> +    VgidTable vgid_table;
>> +    int i;
>> +
>> +    off = acpi_find_rsdp_address();
>> +    g_assert_cmphex(off, <, 0x100000);
> something's off here,
> it fails for me for me with:
> 
> QTEST_QEMU_BINARY=x86_64-softmmu/qemu-system-x86_64 tests/vmgenid-test
> /x86_64/vmgenid/vmgenid: **
> ERROR:/home/imammedo/builds/qemu/tests/vmgenid-test.c:47:acpi_find_vgia: assertion failed (off < 0x100000): (0x00100000 < 0x00100000)
> 
Probably a timing issue.  I’ll get to the bottom of it ASAP

>> +
>> +    acpi_parse_rsdp_table(off, &rsdp_table);
>> +
>> +    rsdt = rsdp_table.rsdt_physical_address;
>> +    /* read the header */
>> +    ACPI_READ_TABLE_HEADER(&rsdt_table, rsdt);
>> +    ACPI_ASSERT_CMP(rsdt_table.signature, "RSDT");
>> +
>> +    /* compute the table entries in rsdt */
>> +    tables_nr = (rsdt_table.length - sizeof(AcpiRsdtDescriptorRev1)) /
>> +                sizeof(uint32_t);
>> +    g_assert_cmpint(tables_nr, >, 0);
>> +
>> +    /* get the addresses of the tables pointed by rsdt */
>> +    tables = g_new0(uint32_t, tables_nr);
>> +    ACPI_READ_ARRAY_PTR(tables, tables_nr, rsdt);
>> +
>> +    for (i = 0; i < tables_nr; i++) {
>> +        ACPI_READ_TABLE_HEADER(&ssdt_table, tables[i]);
>> +        if (!strncmp((char *)ssdt_table.oem_table_id, "VMGENID", 7)) {
>> +            /* the first entry in the table should be VGIA
>> +             * That's all we need
>> +             */
>> +            ACPI_READ_FIELD(vgid_table.name_op, tables[i]);
>> +            g_assert(vgid_table.name_op == 0x08);  /* name */
>> +            ACPI_READ_ARRAY(vgid_table.vgia, tables[i]);
>> +            g_assert(memcmp(vgid_table.vgia, "VGIA", 4) == 0);
>> +            ACPI_READ_FIELD(vgid_table.val_op, tables[i]);
>> +            g_assert(vgid_table.val_op == 0x0C);  /* dword */
>> +            ACPI_READ_FIELD(vgid_table.vgia_val, tables[i]);
>> +            /* The GUID is written at a fixed offset into the fw_cfg file
>> +             * in order to implement the "OVMF SDT Header probe suppressor"
>> +             * see docs/specs/vmgenid.txt for more details
>> +             */
>> +            return vgid_table.vgia_val + VMGENID_GUID_OFFSET;
>> +        }
>> +    }
>> +    return 0;
>> +}
>> +
>> +static void read_guid_from_memory(QemuUUID *guid)
>> +{
>> +    uint32_t vmgenid_addr;
>> +    int i;
>> +
>> +    vmgenid_addr = acpi_find_vgia();
>> +    g_assert(vmgenid_addr);
>> +
>> +    /* Read the GUID directly from guest memory */
>> +    for (i = 0; i < 16; i++) {
>> +        guid->data[i] = readb(vmgenid_addr + i);
>> +    }
>> +    /* The GUID is in little-endian format in the guest, while QEMU
>> +     * uses big-endian.  Swap after reading.
>> +     */
>> +    qemu_uuid_bswap(guid);
>> +}
>> +
>> +static void read_guid_from_monitor(QemuUUID *guid)
>> +{
>> +    QDict *rsp, *rsp_ret;
>> +    const char *guid_str;
>> +
>> +    rsp = qmp("{ 'execute': 'query-vm-generation-id' }");
>> +    if (qdict_haskey(rsp, "return")) {
>> +        rsp_ret = qdict_get_qdict(rsp, "return");
>> +        g_assert(qdict_haskey(rsp_ret, "guid"));
>> +        guid_str = qdict_get_str(rsp_ret, "guid");
>> +        g_assert(qemu_uuid_parse(guid_str, guid) == 0);
>> +    }
>> +    QDECREF(rsp);
>> +}
>> +
>> +static void vmgenid_test(void)
>> +{
>> +    QemuUUID expected, measured;
>> +    gchar *cmd;
>> +
>> +    g_assert(qemu_uuid_parse(VGID_GUID, &expected) == 0);
>> +
>> +    cmd = g_strdup_printf("-machine accel=tcg -device vmgenid,id=testvgid,"
>> +                          "guid=%s", VGID_GUID);
>> +    qtest_start(cmd);
>> +
>> +    /* Read the GUID from accessing guest memory */
>> +    read_guid_from_memory(&measured);
>> +    g_assert(memcmp(measured.data, expected.data, sizeof(measured.data)) == 0);
>> +
>> +    /* Read the GUID via the monitor */
>> +    read_guid_from_monitor(&measured);
>> +    g_assert(memcmp(measured.data, expected.data, sizeof(measured.data)) == 0);
>> +
>> +    qtest_quit(global_qtest);
>> +    g_free(cmd);
>> +}
>> +
>> +static void vmgenid_set_guid_auto_test(void)
>> +{
>> +    const char *cmd;
>> +    QemuUUID measured;
>> +
>> +    cmd = "-machine accel=tcg -device vmgenid,id=testvgid," "guid=auto";
>> +    qtest_start(cmd);
>> +
>> +    read_guid_from_memory(&measured);
>> +
>> +    /* Just check that the GUID is non-null */
>> +    g_assert(!qemu_uuid_is_null(&measured));
>> +
>> +    qtest_quit(global_qtest);
>> +}
>> +
>> +int main(int argc, char **argv)
>> +{
>> +    int ret;
>> +
>> +    g_test_init(&argc, &argv, NULL);
>> +
>> +    qtest_add_func("/vmgenid/vmgenid", vmgenid_test);
>> +    qtest_add_func("/vmgenid/vmgenid/set-guid-auto",
>> +                   vmgenid_set_guid_auto_test);
>> +    ret = g_test_run();
>> +
>> +    qtest_end();
>> +
>> +    return ret;
>> +}

Patch

diff --git a/tests/Makefile.include b/tests/Makefile.include
index 143507e..8d36341 100644
--- a/tests/Makefile.include
+++ b/tests/Makefile.include
@@ -241,6 +241,7 @@  check-qtest-i386-y += tests/usb-hcd-xhci-test$(EXESUF)
 gcov-files-i386-y += hw/usb/hcd-xhci.c
 check-qtest-i386-y += tests/pc-cpu-test$(EXESUF)
 check-qtest-i386-y += tests/q35-test$(EXESUF)
+check-qtest-i386-y += tests/vmgenid-test$(EXESUF)
 gcov-files-i386-y += hw/pci-host/q35.c
 check-qtest-i386-$(CONFIG_VHOST_NET_TEST_i386) += tests/vhost-user-test$(EXESUF)
 ifeq ($(CONFIG_VHOST_NET_TEST_i386),)
@@ -726,6 +727,7 @@  tests/ivshmem-test$(EXESUF): tests/ivshmem-test.o contrib/ivshmem-server/ivshmem
 tests/vhost-user-bridge$(EXESUF): tests/vhost-user-bridge.o contrib/libvhost-user/libvhost-user.o $(test-util-obj-y)
 tests/test-uuid$(EXESUF): tests/test-uuid.o $(test-util-obj-y)
 tests/test-arm-mptimer$(EXESUF): tests/test-arm-mptimer.o
+tests/vmgenid-test$(EXESUF): tests/vmgenid-test.o tests/acpi-utils.o
 
 tests/migration/stress$(EXESUF): tests/migration/stress.o
 	$(call quiet-command, $(LINKPROG) -static -O3 $(PTHREAD_LIB) -o $@ $< ,"LINK","$(TARGET_DIR)$@")
diff --git a/tests/vmgenid-test.c b/tests/vmgenid-test.c
new file mode 100644
index 0000000..1741455
--- /dev/null
+++ b/tests/vmgenid-test.c
@@ -0,0 +1,174 @@ 
+/*
+ * QTest testcase for VM Generation ID
+ *
+ * Copyright (c) 2016 Red Hat, Inc.
+ * Copyright (c) 2017 Skyport Systems
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ */
+
+#include <glib.h>
+#include <string.h>
+#include <unistd.h>
+#include "qemu/osdep.h"
+#include "qemu/bitmap.h"
+#include "qemu/uuid.h"
+#include "hw/acpi/acpi-defs.h"
+#include "acpi-utils.h"
+#include "libqtest.h"
+
+#define VGID_GUID "324e6eaf-d1d1-4bf6-bf41-b9bb6c91fb87"
+#define VMGENID_GUID_OFFSET      40   /* allow space for
+                                       * OVMF SDT Header Probe Supressor
+                                       */
+
+typedef struct {
+    AcpiTableHeader header;
+    gchar name_op;
+    gchar vgia[4];
+    gchar val_op;
+    uint32_t vgia_val;
+} QEMU_PACKED VgidTable;
+
+static uint32_t acpi_find_vgia(void)
+{
+    uint32_t off;
+    AcpiRsdpDescriptor rsdp_table;
+    uint32_t rsdt;
+    AcpiRsdtDescriptorRev1 rsdt_table;
+    int tables_nr;
+    uint32_t *tables;
+    AcpiTableHeader ssdt_table;
+    VgidTable vgid_table;
+    int i;
+
+    off = acpi_find_rsdp_address();
+    g_assert_cmphex(off, <, 0x100000);
+
+    acpi_parse_rsdp_table(off, &rsdp_table);
+
+    rsdt = rsdp_table.rsdt_physical_address;
+    /* read the header */
+    ACPI_READ_TABLE_HEADER(&rsdt_table, rsdt);
+    ACPI_ASSERT_CMP(rsdt_table.signature, "RSDT");
+
+    /* compute the table entries in rsdt */
+    tables_nr = (rsdt_table.length - sizeof(AcpiRsdtDescriptorRev1)) /
+                sizeof(uint32_t);
+    g_assert_cmpint(tables_nr, >, 0);
+
+    /* get the addresses of the tables pointed by rsdt */
+    tables = g_new0(uint32_t, tables_nr);
+    ACPI_READ_ARRAY_PTR(tables, tables_nr, rsdt);
+
+    for (i = 0; i < tables_nr; i++) {
+        ACPI_READ_TABLE_HEADER(&ssdt_table, tables[i]);
+        if (!strncmp((char *)ssdt_table.oem_table_id, "VMGENID", 7)) {
+            /* the first entry in the table should be VGIA
+             * That's all we need
+             */
+            ACPI_READ_FIELD(vgid_table.name_op, tables[i]);
+            g_assert(vgid_table.name_op == 0x08);  /* name */
+            ACPI_READ_ARRAY(vgid_table.vgia, tables[i]);
+            g_assert(memcmp(vgid_table.vgia, "VGIA", 4) == 0);
+            ACPI_READ_FIELD(vgid_table.val_op, tables[i]);
+            g_assert(vgid_table.val_op == 0x0C);  /* dword */
+            ACPI_READ_FIELD(vgid_table.vgia_val, tables[i]);
+            /* The GUID is written at a fixed offset into the fw_cfg file
+             * in order to implement the "OVMF SDT Header probe suppressor"
+             * see docs/specs/vmgenid.txt for more details
+             */
+            return vgid_table.vgia_val + VMGENID_GUID_OFFSET;
+        }
+    }
+    return 0;
+}
+
+static void read_guid_from_memory(QemuUUID *guid)
+{
+    uint32_t vmgenid_addr;
+    int i;
+
+    vmgenid_addr = acpi_find_vgia();
+    g_assert(vmgenid_addr);
+
+    /* Read the GUID directly from guest memory */
+    for (i = 0; i < 16; i++) {
+        guid->data[i] = readb(vmgenid_addr + i);
+    }
+    /* The GUID is in little-endian format in the guest, while QEMU
+     * uses big-endian.  Swap after reading.
+     */
+    qemu_uuid_bswap(guid);
+}
+
+static void read_guid_from_monitor(QemuUUID *guid)
+{
+    QDict *rsp, *rsp_ret;
+    const char *guid_str;
+
+    rsp = qmp("{ 'execute': 'query-vm-generation-id' }");
+    if (qdict_haskey(rsp, "return")) {
+        rsp_ret = qdict_get_qdict(rsp, "return");
+        g_assert(qdict_haskey(rsp_ret, "guid"));
+        guid_str = qdict_get_str(rsp_ret, "guid");
+        g_assert(qemu_uuid_parse(guid_str, guid) == 0);
+    }
+    QDECREF(rsp);
+}
+
+static void vmgenid_test(void)
+{
+    QemuUUID expected, measured;
+    gchar *cmd;
+
+    g_assert(qemu_uuid_parse(VGID_GUID, &expected) == 0);
+
+    cmd = g_strdup_printf("-machine accel=tcg -device vmgenid,id=testvgid,"
+                          "guid=%s", VGID_GUID);
+    qtest_start(cmd);
+
+    /* Read the GUID from accessing guest memory */
+    read_guid_from_memory(&measured);
+    g_assert(memcmp(measured.data, expected.data, sizeof(measured.data)) == 0);
+
+    /* Read the GUID via the monitor */
+    read_guid_from_monitor(&measured);
+    g_assert(memcmp(measured.data, expected.data, sizeof(measured.data)) == 0);
+
+    qtest_quit(global_qtest);
+    g_free(cmd);
+}
+
+static void vmgenid_set_guid_auto_test(void)
+{
+    const char *cmd;
+    QemuUUID measured;
+
+    cmd = "-machine accel=tcg -device vmgenid,id=testvgid," "guid=auto";
+    qtest_start(cmd);
+
+    read_guid_from_memory(&measured);
+
+    /* Just check that the GUID is non-null */
+    g_assert(!qemu_uuid_is_null(&measured));
+
+    qtest_quit(global_qtest);
+}
+
+int main(int argc, char **argv)
+{
+    int ret;
+
+    g_test_init(&argc, &argv, NULL);
+
+    qtest_add_func("/vmgenid/vmgenid", vmgenid_test);
+    qtest_add_func("/vmgenid/vmgenid/set-guid-auto",
+                   vmgenid_set_guid_auto_test);
+    ret = g_test_run();
+
+    qtest_end();
+
+    return ret;
+}