Merge remote-tracking branch 'remotes/elmarco/tags/dbus-vmstate7-pull-request' into staging

Add dbus-vmstate

Hi,

With external processes or helpers participating to the VM support, it
becomes necessary to handle their migration. Various options exist to
transfer their state:
1) as the VM memory, RAM or devices (we could say that's how
   vhost-user devices can be handled today, they are expected to
   restore from ring state)
2) other "vmstate" (as with TPM emulator state blobs)
3) left to be handled by management layer

1) is not practical, since an external processes may legitimatelly
need arbitrary state date to back a device or a service, or may not
even have an associated device.

2) needs ad-hoc code for each helper, but is simple and working

3) is complicated for management layer, QEMU has the migration timing

The proposed "dbus-vmstate" object will connect to a given D-Bus
address, and save/load from org.qemu.VMState1 owners on migration.

Thus helpers can easily have their state migrated with QEMU, without
implementing ad-hoc support (such as done for TPM emulation)

D-Bus is ubiquitous on Linux (it is systemd IPC), and can be made to
work on various other OSes. There are several implementations and good
bindings for various languages.  (the tests/dbus-vmstate-test.c is a
good example of how simple the implementation of services can be, even
in C)

dbus-vmstate is put into use by the libvirt series "[PATCH 00/23] Use
a slirp helper process".

v2:
 - fix build with broken mingw-glib

# gpg: Signature made Mon 06 Jan 2020 14:43:35 GMT
# gpg:                using RSA key 87A9BD933F87C606D276F62DDAE8E10975969CE5
# gpg:                issuer "marcandre.lureau@redhat.com"
# gpg: Good signature from "Marc-André Lureau <marcandre.lureau@redhat.com>" [full]
# gpg:                 aka "Marc-André Lureau <marcandre.lureau@gmail.com>" [full]
# Primary key fingerprint: 87A9 BD93 3F87 C606 D276  F62D DAE8 E109 7596 9CE5

* remotes/elmarco/tags/dbus-vmstate7-pull-request:
  tests: add dbus-vmstate-test
  tests: add migration-helpers unit
  dockerfiles: add dbus-daemon to some of latest distributions
  configure: add GDBUS_CODEGEN
  Add dbus-vmstate object
  util: add dbus helper unit
  docs: start a document to describe D-Bus usage
  vmstate: replace DeviceState with VMStateIf
  vmstate: add qom interface to get id

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

1 files changed, 11 insertions, 165 deletions

diff --git a/tests/migration-test.c b/tests/migration-test.c
index e56e6dcb00..53afec4395 100644
--- a/tests/migration-test.c
+++ b/tests/migration-test.c
@@ -14,7 +14,6 @@
 
 #include "libqtest.h"
 #include "qapi/qmp/qdict.h"
-#include "qapi/qmp/qjson.h"
 #include "qemu/module.h"
 #include "qemu/option.h"
 #include "qemu/range.h"
@@ -24,6 +23,7 @@
 #include "qapi/qobject-input-visitor.h"
 #include "qapi/qobject-output-visitor.h"
 
+#include "migration-helpers.h"
 #include "migration/migration-test.h"
 
 /* TODO actually test the results and get rid of this */
@@ -31,7 +31,6 @@
 
 unsigned start_address;
 unsigned end_address;
-bool got_stop;
 static bool uffd_feature_thread_id;
 
 #if defined(__linux__)
@@ -157,67 +156,6 @@ static void wait_for_serial(const char *side)
     } while (true);
 }
 
-static void stop_cb(void *opaque, const char *name, QDict *data)
-{
-    if (!strcmp(name, "STOP")) {
-        got_stop = true;
-    }
-}
-
-/*
- * Events can get in the way of responses we are actually waiting for.
- */
-GCC_FMT_ATTR(3, 4)
-static QDict *wait_command_fd(QTestState *who, int fd, const char *command, ...)
-{
-    va_list ap;
-
-    va_start(ap, command);
-    qtest_qmp_vsend_fds(who, &fd, 1, command, ap);
-    va_end(ap);
-
-    return qtest_qmp_receive_success(who, stop_cb, NULL);
-}
-
-/*
- * Events can get in the way of responses we are actually waiting for.
- */
-GCC_FMT_ATTR(2, 3)
-static QDict *wait_command(QTestState *who, const char *command, ...)
-{
-    va_list ap;
-
-    va_start(ap, command);
-    qtest_qmp_vsend(who, command, ap);
-    va_end(ap);
-
-    return qtest_qmp_receive_success(who, stop_cb, NULL);
-}
-
-/*
- * Note: caller is responsible to free the returned object via
- * qobject_unref() after use
- */
-static QDict *migrate_query(QTestState *who)
-{
-    return wait_command(who, "{ 'execute': 'query-migrate' }");
-}
-
-/*
- * Note: caller is responsible to free the returned object via
- * g_free() after use
- */
-static gchar *migrate_query_status(QTestState *who)
-{
-    QDict *rsp_return = migrate_query(who);
-    gchar *status = g_strdup(qdict_get_str(rsp_return, "status"));
-
-    g_assert(status);
-    qobject_unref(rsp_return);
-
-    return status;
-}
-
 /*
  * It's tricky to use qemu's migration event capability with qtest,
  * events suddenly appearing confuse the qmp()/hmp() responses.
@@ -265,48 +203,6 @@ static void read_blocktime(QTestState *who)
     qobject_unref(rsp_return);
 }
 
-static bool check_migration_status(QTestState *who, const char *goal,
-                                   const char **ungoals)
-{
-    bool ready;
-    char *current_status;
-    const char **ungoal;
-
-    current_status = migrate_query_status(who);
-    ready = strcmp(current_status, goal) == 0;
-    if (!ungoals) {
-        g_assert_cmpstr(current_status, !=, "failed");
-        /*
-         * If looking for a state other than completed,
-         * completion of migration would cause the test to
-         * hang.
-         */
-        if (strcmp(goal, "completed") != 0) {
-            g_assert_cmpstr(current_status, !=, "completed");
-        }
-    } else {
-        for (ungoal = ungoals; *ungoal; ungoal++) {
-            g_assert_cmpstr(current_status, !=,  *ungoal);
-        }
-    }
-    g_free(current_status);
-    return ready;
-}
-
-static void wait_for_migration_status(QTestState *who,
-                                      const char *goal,
-                                      const char **ungoals)
-{
-    while (!check_migration_status(who, goal, ungoals)) {
-        usleep(1000);
-    }
-}
-
-static void wait_for_migration_complete(QTestState *who)
-{
-    wait_for_migration_status(who, "completed", NULL);
-}
-
 static void wait_for_migration_pass(QTestState *who)
 {
     uint64_t initial_pass = get_migration_pass(who);
@@ -506,30 +402,6 @@ static void migrate_set_capability(QTestState *who, const char *capability,
     qobject_unref(rsp);
 }
 
-/*
- * Send QMP command "migrate".
- * Arguments are built from @fmt... (formatted like
- * qobject_from_jsonf_nofail()) with "uri": @uri spliced in.
- */
-GCC_FMT_ATTR(3, 4)
-static void migrate(QTestState *who, const char *uri, const char *fmt, ...)
-{
-    va_list ap;
-    QDict *args, *rsp;
-
-    va_start(ap, fmt);
-    args = qdict_from_vjsonf_nofail(fmt, ap);
-    va_end(ap);
-
-    g_assert(!qdict_haskey(args, "uri"));
-    qdict_put_str(args, "uri", uri);
-
-    rsp = qtest_qmp(who, "{ 'execute': 'migrate', 'arguments': %p}", args);
-
-    g_assert(qdict_haskey(rsp, "return"));
-    qobject_unref(rsp);
-}
-
 static void migrate_postcopy_start(QTestState *from, QTestState *to)
 {
     QDict *rsp;
@@ -800,7 +672,7 @@ static int migrate_postcopy_prepare(QTestState **from_ptr,
     /* Wait for the first serial output from the source */
     wait_for_serial("src_serial");
 
-    migrate(from, uri, "{}");
+    migrate_qmp(from, uri, "{}");
     g_free(uri);
 
     wait_for_migration_pass(from);
@@ -891,7 +763,7 @@ static void test_postcopy_recovery(void)
     wait_for_migration_status(from, "postcopy-paused",
                               (const char * []) { "failed", "active",
                                                   "completed", NULL });
-    migrate(from, uri, "{'resume': true}");
+    migrate_qmp(from, uri, "{'resume': true}");
     g_free(uri);
 
     /* Restore the postcopy bandwidth to unlimited */
@@ -900,32 +772,6 @@ static void test_postcopy_recovery(void)
     migrate_postcopy_complete(from, to);
 }
 
-static void wait_for_migration_fail(QTestState *from, bool allow_active)
-{
-    QDict *rsp_return;
-    char *status;
-    bool failed;
-
-    do {
-        status = migrate_query_status(from);
-        bool result = !strcmp(status, "setup") || !strcmp(status, "failed") ||
-                 (allow_active && !strcmp(status, "active"));
-        if (!result) {
-            fprintf(stderr, "%s: unexpected status status=%s allow_active=%d\n",
-                    __func__, status, allow_active);
-        }
-        g_assert(result);
-        failed = !strcmp(status, "failed");
-        g_free(status);
-    } while (!failed);
-
-    /* Is the machine currently running? */
-    rsp_return = wait_command(from, "{ 'execute': 'query-status' }");
-    g_assert(qdict_haskey(rsp_return, "running"));
-    g_assert(qdict_get_bool(rsp_return, "running"));
-    qobject_unref(rsp_return);
-}
-
 static void test_baddest(void)
 {
     MigrateStart *args = migrate_start_new();
@@ -936,7 +782,7 @@ static void test_baddest(void)
     if (test_migrate_start(&from, &to, "tcp:0:0", args)) {
         return;
     }
-    migrate(from, "tcp:0:0", "{}");
+    migrate_qmp(from, "tcp:0:0", "{}");
     wait_for_migration_fail(from, false);
     test_migrate_end(from, to, false);
 }
@@ -963,7 +809,7 @@ static void test_precopy_unix(void)
     /* Wait for the first serial output from the source */
     wait_for_serial("src_serial");
 
-    migrate(from, uri, "{}");
+    migrate_qmp(from, uri, "{}");
 
     wait_for_migration_pass(from);
 
@@ -1000,7 +846,7 @@ static void test_ignore_shared(void)
     /* Wait for the first serial output from the source */
     wait_for_serial("src_serial");
 
-    migrate(from, uri, "{}");
+    migrate_qmp(from, uri, "{}");
 
     wait_for_migration_pass(from);
 
@@ -1047,7 +893,7 @@ static void test_xbzrle(const char *uri)
     /* Wait for the first serial output from the source */
     wait_for_serial("src_serial");
 
-    migrate(from, uri, "{}");
+    migrate_qmp(from, uri, "{}");
 
     wait_for_migration_pass(from);
 
@@ -1098,7 +944,7 @@ static void test_precopy_tcp(void)
 
     uri = migrate_get_socket_address(to, "socket-address");
 
-    migrate(from, uri, "{}");
+    migrate_qmp(from, uri, "{}");
 
     wait_for_migration_pass(from);
 
@@ -1167,7 +1013,7 @@ static void test_migrate_fd_proto(void)
     close(pair[1]);
 
     /* Start migration to the 2nd socket*/
-    migrate(from, "fd:fd-mig", "{}");
+    migrate_qmp(from, "fd:fd-mig", "{}");
 
     wait_for_migration_pass(from);
 
@@ -1222,7 +1068,7 @@ static void do_test_validate_uuid(MigrateStart *args, bool should_fail)
     /* Wait for the first serial output from the source */
     wait_for_serial("src_serial");
 
-    migrate(from, uri, "{}");
+    migrate_qmp(from, uri, "{}");
 
     if (should_fail) {
         qtest_set_expected_status(to, 1);
@@ -1316,7 +1162,7 @@ static void test_migrate_auto_converge(void)
     /* Wait for the first serial output from the source */
     wait_for_serial("src_serial");
 
-    migrate(from, uri, "{}");
+    migrate_qmp(from, uri, "{}");
 
     /* Wait for throttling begins */
     percentage = 0;