[Qemu-devel] [PATCH] vmgenid: allow VM Generation ID modification via QMP/HMP

[Or Idgar <idgar@virtualoco.com>]

From: Or Idgar <oidgar@redhat.com>

This patch allow changing the Virtual Machine Generation
ID through QMP/HMP while the vm guest is running.
As the definition block of VMGENID in ACPI includes the
"Notify" method, we can use it to notify the guest about
ID changes.

QMP command example:
    { "execute": "set-vm-generation-id",
          "arguments": {
              "guid": "324e6eaf-d1d1-4bf6-bf41-b9bb6c91fb87"
          }
    }

HMP command example:
    set-vm-generation-id 324e6eaf-d1d1-4bf6-bf41-b9bb6c91fb87

This patch is based off an earlier version by
Igor Mammedov (imammedo@redhat.com)

Signed-off-by: Or Idgar <oidgar@redhat.com>
Reviewed-by: Gal Hammer <ghammer@redhat.com>
---
 docs/specs/vmgenid.txt |  7 ++++---
 hmp-commands.hx        | 13 +++++++++++++
 hmp.c                  | 10 ++++++++++
 hmp.h                  |  1 +
 hw/acpi/vmgenid.c      | 10 ++++++++++
 qapi-schema.json       | 11 +++++++++++
 tests/vmgenid-test.c   | 31 +++++++++++++++++++++++++++++++
 7 files changed, 80 insertions(+), 3 deletions(-)

diff --git a/docs/specs/vmgenid.txt b/docs/specs/vmgenid.txt
index aa9f518..04443de 100644
--- a/docs/specs/vmgenid.txt
+++ b/docs/specs/vmgenid.txt
@@ -240,6 +240,7 @@ The property may be queried via QMP/HMP:
   (QEMU) query-vm-generation-id
   {"return": {"guid": "324e6eaf-d1d1-4bf6-bf41-b9bb6c91fb87"}}
 
-Setting of this parameter is intentionally left out from the QMP/HMP
-interfaces.  There are no known use cases for changing the GUID once QEMU is
-running, and adding this capability would greatly increase the complexity.
+Also, the property may be set via QMP/HMP:
+
+  (QEMU) set-vm-generation-id guid=ee6726ce-73b4-4a8b-863c-708f26515847
+  {"return": {}}
diff --git a/hmp-commands.hx b/hmp-commands.hx
index 4afd57c..4524669 100644
--- a/hmp-commands.hx
+++ b/hmp-commands.hx
@@ -1871,5 +1871,18 @@ ETEXI
     },
 
 STEXI
+@item set-vm-generation-id @var{uuid}
+Set Virtual Machine Generation ID counter to @var{guid}
+ETEXI
+
+    {
+        .name       = "set-vm-generation-id",
+        .args_type  = "guid:s",
+        .params     = "guid",
+        .help       = "Set Virtual Machine Generation ID counter",
+        .cmd        = hmp_set_vm_generation_id,
+    },
+
+STEXI
 @end table
 ETEXI
diff --git a/hmp.c b/hmp.c
index 35a7041..73f9b00 100644
--- a/hmp.c
+++ b/hmp.c
@@ -2901,6 +2901,16 @@ void hmp_info_vm_generation_id(Monitor *mon, const QDict *qdict)
     qapi_free_GuidInfo(info);
 }
 
+void hmp_set_vm_generation_id(Monitor *mon, const QDict *qdict)
+{
+    Error *errp = NULL;
+    const char *guid = qdict_get_str(qdict, "guid");
+
+    qmp_set_vm_generation_id(guid, &errp);
+    if (errp)
+        hmp_handle_error(mon, &errp);
+}
+
 void hmp_info_memory_size_summary(Monitor *mon, const QDict *qdict)
 {
     Error *err = NULL;
diff --git a/hmp.h b/hmp.h
index a6f56b1..8cc74d5 100644
--- a/hmp.h
+++ b/hmp.h
@@ -147,5 +147,6 @@ void hmp_info_ramblock(Monitor *mon, const QDict *qdict);
 void hmp_hotpluggable_cpus(Monitor *mon, const QDict *qdict);
 void hmp_info_vm_generation_id(Monitor *mon, const QDict *qdict);
 void hmp_info_memory_size_summary(Monitor *mon, const QDict *qdict);
+void hmp_set_vm_generation_id(Monitor *mon, const QDict *qdict);
 
 #endif
diff --git a/hw/acpi/vmgenid.c b/hw/acpi/vmgenid.c
index 105044f..5319d70 100644
--- a/hw/acpi/vmgenid.c
+++ b/hw/acpi/vmgenid.c
@@ -129,6 +129,16 @@ void vmgenid_add_fw_cfg(VmGenIdState *vms, FWCfgState *s, GArray *guid)
                              ARRAY_SIZE(vms->vmgenid_addr_le), false);
 }
 
+void qmp_set_vm_generation_id(const char *guid, Error **errp)
+{
+    Object *obj = find_vmgenid_dev();
+
+    if (!obj) {
+        return;
+    }
+    object_property_set_str(obj, guid, VMGENID_GUID, errp);
+}
+
 static void vmgenid_update_guest(VmGenIdState *vms)
 {
     Object *obj = object_resolve_path_type("", TYPE_ACPI_DEVICE_IF, NULL);
diff --git a/qapi-schema.json b/qapi-schema.json
index 1845795..c2ab733 100644
--- a/qapi-schema.json
+++ b/qapi-schema.json
@@ -3193,6 +3193,17 @@
 { 'command': 'query-vm-generation-id', 'returns': 'GuidInfo' }
 
 ##
+# @set-vm-generation-id:
+#
+# Set Virtual Machine Generation ID
+#
+# @guid: new GUID to set as Virtual Machine Generation ID
+#
+# Since 2.12
+##
+{ 'command': 'set-vm-generation-id', 'data': { 'guid': 'str' } }
+
+##
 # @watchdog-set-action:
 #
 # Set watchdog action
diff --git a/tests/vmgenid-test.c b/tests/vmgenid-test.c
index 5a86b40..544cf0f 100644
--- a/tests/vmgenid-test.c
+++ b/tests/vmgenid-test.c
@@ -130,6 +130,24 @@ static void read_guid_from_monitor(QemuUUID *guid)
     QDECREF(rsp);
 }
 
+static void set_guid_via_monitor(QemuUUID *guid)
+{
+    QDict *rsp, *rsp_ret;
+    char command[256];
+    char *guid_str;
+
+    guid_str = qemu_uuid_unparse_strdup(guid);
+    sprintf(command, "{ 'execute': 'set-vm-generation-id', 'arguments': \
+                      { 'guid': '%s' } }",
+            guid_str);
+    free(guid_str);
+    rsp = qmp(command);
+    if (qdict_haskey(rsp, "return")) {
+        rsp_ret = qdict_get_qdict(rsp, "return");
+        g_assert(qdict_size(rsp_ret) == 0);
+    }
+}
+
 static char disk[] = "tests/vmgenid-test-disk-XXXXXX";
 
 #define GUID_CMD(guid)                          \
@@ -182,6 +200,17 @@ static void vmgenid_query_monitor_test(void)
     qtest_quit(global_qtest);
 }
 
+static void vmgenid_set_monitor_test(void)
+{
+    QemuUUID expected, measured;
+
+    global_qtest = qtest_startf(GUID_CMD(VGID_GUID));
+    qemu_uuid_generate(&expected);
+    set_guid_via_monitor(&expected);
+    read_guid_from_monitor(&measured);
+    g_assert(memcmp(measured.data, expected.data, sizeof(measured.data)) == 0);
+}
+
 int main(int argc, char **argv)
 {
     int ret;
@@ -199,6 +228,8 @@ int main(int argc, char **argv)
                    vmgenid_set_guid_auto_test);
     qtest_add_func("/vmgenid/vmgenid/query-monitor",
                    vmgenid_query_monitor_test);
+    qtest_add_func("/vmgenid/vmgenid/set-guid-qmp",
+                   vmgenid_set_monitor_test);
     ret = g_test_run();
     boot_sector_cleanup(disk);
 
-- 
2.9.5