[Qemu-devel] [PATCH v2 0/2] Deferred incoming migration through fd

[Qemu-devel] [PATCH v2 0/2] Deferred incoming migration through fd

[Yury Kotov]

Hi,

V2:
* Revert odd changes in migrate()
* Add short description for socket_send_fds()
  and remove ifdef WIN32 as it's not needed

This series is a continuation of the previous two:
* migration: Fix handling fd protocol
* Add 'inline-fd:' protocol for migration

It's about such use case:
1. Target VM: exec ...,-incoming defer
2. Target VM: getfd("fd-mig")
3. Target VM: migrate-incoming("fd:"fd-mig")
4. Source VM: getfd("fd-mig")
5. Source VM: migrate("fd-mig")

Currently, it's not possible to do the step 3, because for incoming migration
"fd:" protocol expects an integer, not the name of fd.

Yury Kotov (2):
  migration: Fix fd protocol for incoming defer
  migration-test: Add a test for fd protocol

 migration/fd.c         |   8 ++--
 migration/fd.h         |   2 +-
 tests/libqtest.c       |  80 ++++++++++++++++++++++++++++++--
 tests/libqtest.h       |  51 ++++++++++++++++++++-
 tests/migration-test.c | 101 +++++++++++++++++++++++++++++++++++++++++
 5 files changed, 233 insertions(+), 9 deletions(-)

-- 
2.21.0

[Qemu-devel] [PATCH v2 1/2] migration: Fix fd protocol for incoming defer

[Yury Kotov]

Currently, incoming migration through fd supports only command-line case:
E.g.
    fork();
    fd = open();
    exec("qemu ... -incoming fd:%d", fd);

It's possible to use add-fd commands to pass fd for migration, but it's
invalid case. add-fd works with fdset but not with particular fds.

To work with getfd in incoming defer it's enough to use monitor_fd_param
instead of strtol. monitor_fd_param supports both cases:
* fd:123
* fd:fd_name (added by getfd).

And also the use of monitor_fd_param improves error messages.

Signed-off-by: Yury Kotov <yury-kotov@yandex-team.ru>
Reviewed-by: Juan Quintela <quintela@redhat.com>
---
 migration/fd.c | 8 +++++---
 migration/fd.h | 2 +-
 2 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/migration/fd.c b/migration/fd.c
index a7c13df4ad..0a29ecdebf 100644
--- a/migration/fd.c
+++ b/migration/fd.c
@@ -52,12 +52,14 @@ static gboolean fd_accept_incoming_migration(QIOChannel *ioc,
     return G_SOURCE_REMOVE;
 }
 
-void fd_start_incoming_migration(const char *infd, Error **errp)
+void fd_start_incoming_migration(const char *fdname, Error **errp)
 {
     QIOChannel *ioc;
-    int fd;
+    int fd = monitor_fd_param(cur_mon, fdname, errp);
+    if (fd == -1) {
+        return;
+    }
 
-    fd = strtol(infd, NULL, 0);
     trace_migration_fd_incoming(fd);
 
     ioc = qio_channel_new_fd(fd, errp);
diff --git a/migration/fd.h b/migration/fd.h
index a14a63ce2e..b901bc014e 100644
--- a/migration/fd.h
+++ b/migration/fd.h
@@ -16,7 +16,7 @@
 
 #ifndef QEMU_MIGRATION_FD_H
 #define QEMU_MIGRATION_FD_H
-void fd_start_incoming_migration(const char *path, Error **errp);
+void fd_start_incoming_migration(const char *fdname, Error **errp);
 
 void fd_start_outgoing_migration(MigrationState *s, const char *fdname,
                                  Error **errp);
-- 
2.21.0

[Qemu-devel] [PATCH v2 2/2] migration-test: Add a test for fd protocol

[Yury Kotov]

Signed-off-by: Yury Kotov <yury-kotov@yandex-team.ru>
---
 tests/libqtest.c       |  80 ++++++++++++++++++++++++++++++--
 tests/libqtest.h       |  51 ++++++++++++++++++++-
 tests/migration-test.c | 101 +++++++++++++++++++++++++++++++++++++++++
 3 files changed, 227 insertions(+), 5 deletions(-)

diff --git a/tests/libqtest.c b/tests/libqtest.c
index 8ac0c02af4..64f65bea22 100644
--- a/tests/libqtest.c
+++ b/tests/libqtest.c
@@ -32,6 +32,7 @@
 
 #define MAX_IRQ 256
 #define SOCKET_TIMEOUT 50
+#define SOCKET_MAX_FDS 16
 
 QTestState *global_qtest;
 
@@ -391,6 +392,40 @@ static void GCC_FMT_ATTR(2, 3) qtest_sendf(QTestState *s, const char *fmt, ...)
     va_end(ap);
 }
 
+/* Sends a message and file descriptors to the socket.
+ * It's needed for qmp-commands like getfd/add-fd */
+static void socket_send_fds(int socket_fd, int *fds, size_t fds_num,
+                            const char *buf, size_t buf_size)
+{
+    ssize_t ret;
+    struct msghdr msg = { 0 };
+    char control[CMSG_SPACE(sizeof(int) * SOCKET_MAX_FDS)] = { 0 };
+    size_t fdsize = sizeof(int) * fds_num;
+    struct cmsghdr *cmsg;
+    struct iovec iov = { .iov_base = (char *)buf, .iov_len = buf_size };
+
+    msg.msg_iov = &iov;
+    msg.msg_iovlen = 1;
+
+    if (fds && fds_num > 0) {
+        g_assert_cmpuint(fds_num, <, SOCKET_MAX_FDS);
+
+        msg.msg_control = control;
+        msg.msg_controllen = CMSG_SPACE(fdsize);
+
+        cmsg = CMSG_FIRSTHDR(&msg);
+        cmsg->cmsg_len = CMSG_LEN(fdsize);
+        cmsg->cmsg_level = SOL_SOCKET;
+        cmsg->cmsg_type = SCM_RIGHTS;
+        memcpy(CMSG_DATA(cmsg), fds, fdsize);
+    }
+
+    do {
+        ret = sendmsg(socket_fd, &msg, 0);
+    } while (ret < 0 && errno == EINTR);
+    g_assert_cmpint(ret, >, 0);
+}
+
 static GString *qtest_recv_line(QTestState *s)
 {
     GString *line;
@@ -545,7 +580,8 @@ QDict *qtest_qmp_receive(QTestState *s)
  * in the case that they choose to discard all replies up until
  * a particular EVENT is received.
  */
-void qmp_fd_vsend(int fd, const char *fmt, va_list ap)
+void qmp_fd_vsend_fds(int fd, int *fds, size_t fds_num,
+                      const char *fmt, va_list ap)
 {
     QObject *qobj;
 
@@ -569,25 +605,49 @@ void qmp_fd_vsend(int fd, const char *fmt, va_list ap)
             fprintf(stderr, "%s", str);
         }
         /* Send QMP request */
-        socket_send(fd, str, qstring_get_length(qstr));
+        if (fds && fds_num > 0) {
+            socket_send_fds(fd, fds, fds_num, str, qstring_get_length(qstr));
+        } else {
+            socket_send(fd, str, qstring_get_length(qstr));
+        }
 
         qobject_unref(qstr);
         qobject_unref(qobj);
     }
 }
 
+void qmp_fd_vsend(int fd, const char *fmt, va_list ap)
+{
+    qmp_fd_vsend_fds(fd, NULL, 0, fmt, ap);
+}
+
+void qtest_qmp_vsend_fds(QTestState *s, int *fds, size_t fds_num,
+                         const char *fmt, va_list ap)
+{
+    qmp_fd_vsend_fds(s->qmp_fd, fds, fds_num, fmt, ap);
+}
+
 void qtest_qmp_vsend(QTestState *s, const char *fmt, va_list ap)
 {
-    qmp_fd_vsend(s->qmp_fd, fmt, ap);
+    qmp_fd_vsend_fds(s->qmp_fd, NULL, 0, fmt, ap);
 }
 
 QDict *qmp_fdv(int fd, const char *fmt, va_list ap)
 {
-    qmp_fd_vsend(fd, fmt, ap);
+    qmp_fd_vsend_fds(fd, NULL, 0, fmt, ap);
 
     return qmp_fd_receive(fd);
 }
 
+QDict *qtest_vqmp_fds(QTestState *s, int *fds, size_t fds_num,
+                      const char *fmt, va_list ap)
+{
+    qtest_qmp_vsend_fds(s, fds, fds_num, fmt, ap);
+
+    /* Receive reply */
+    return qtest_qmp_receive(s);
+}
+
 QDict *qtest_vqmp(QTestState *s, const char *fmt, va_list ap)
 {
     qtest_qmp_vsend(s, fmt, ap);
@@ -616,6 +676,18 @@ void qmp_fd_send(int fd, const char *fmt, ...)
     va_end(ap);
 }
 
+QDict *qtest_qmp_fds(QTestState *s, int *fds, size_t fds_num,
+                     const char *fmt, ...)
+{
+    va_list ap;
+    QDict *response;
+
+    va_start(ap, fmt);
+    response = qtest_vqmp_fds(s, fds, fds_num, fmt, ap);
+    va_end(ap);
+    return response;
+}
+
 QDict *qtest_qmp(QTestState *s, const char *fmt, ...)
 {
     va_list ap;
diff --git a/tests/libqtest.h b/tests/libqtest.h
index a98ea15b7d..e61ebaced1 100644
--- a/tests/libqtest.h
+++ b/tests/libqtest.h
@@ -84,6 +84,21 @@ QTestState *qtest_init_with_serial(const char *extra_args, int *sock_fd);
  */
 void qtest_quit(QTestState *s);
 
+/**
+ * qtest_qmp_fds:
+ * @s: #QTestState instance to operate on.
+ * @fds: array of file descriptors
+ * @fds_num: number of elements in @fds
+ * @fmt...: QMP message to send to qemu, formatted like
+ * qobject_from_jsonf_nofail().  See parse_escape() for what's
+ * supported after '%'.
+ *
+ * Sends a QMP message to QEMU with fds and returns the response.
+ */
+QDict *qtest_qmp_fds(QTestState *s, int *fds, size_t fds_num,
+                     const char *fmt, ...)
+    GCC_FMT_ATTR(4, 5);
+
 /**
  * qtest_qmp:
  * @s: #QTestState instance to operate on.
@@ -120,7 +135,23 @@ void qtest_qmp_send_raw(QTestState *s, const char *fmt, ...)
     GCC_FMT_ATTR(2, 3);
 
 /**
- * qtest_qmpv:
+ * qtest_vqmp_fds:
+ * @s: #QTestState instance to operate on.
+ * @fds: array of file descriptors
+ * @fds_num: number of elements in @fds
+ * @fmt: QMP message to send to QEMU, formatted like
+ * qobject_from_jsonf_nofail().  See parse_escape() for what's
+ * supported after '%'.
+ * @ap: QMP message arguments
+ *
+ * Sends a QMP message to QEMU with fds and returns the response.
+ */
+QDict *qtest_vqmp_fds(QTestState *s, int *fds, size_t fds_num,
+                      const char *fmt, va_list ap)
+    GCC_FMT_ATTR(4, 0);
+
+/**
+ * qtest_vqmp:
  * @s: #QTestState instance to operate on.
  * @fmt: QMP message to send to QEMU, formatted like
  * qobject_from_jsonf_nofail().  See parse_escape() for what's
@@ -132,6 +163,22 @@ void qtest_qmp_send_raw(QTestState *s, const char *fmt, ...)
 QDict *qtest_vqmp(QTestState *s, const char *fmt, va_list ap)
     GCC_FMT_ATTR(2, 0);
 
+/**
+ * qtest_qmp_vsend_fds:
+ * @s: #QTestState instance to operate on.
+ * @fds: array of file descriptors
+ * @fds_num: number of elements in @fds
+ * @fmt: QMP message to send to QEMU, formatted like
+ * qobject_from_jsonf_nofail().  See parse_escape() for what's
+ * supported after '%'.
+ * @ap: QMP message arguments
+ *
+ * Sends a QMP message to QEMU and leaves the response in the stream.
+ */
+void qtest_qmp_vsend_fds(QTestState *s, int *fds, size_t fds_num,
+                         const char *fmt, va_list ap)
+    GCC_FMT_ATTR(4, 0);
+
 /**
  * qtest_qmp_vsend:
  * @s: #QTestState instance to operate on.
@@ -877,6 +924,8 @@ static inline int64_t clock_step(int64_t step)
 }
 
 QDict *qmp_fd_receive(int fd);
+void qmp_fd_vsend_fds(int fd, int *fds, size_t fds_num,
+                      const char *fmt, va_list ap) GCC_FMT_ATTR(4, 0);
 void qmp_fd_vsend(int fd, const char *fmt, va_list ap) GCC_FMT_ATTR(2, 0);
 void qmp_fd_send(int fd, const char *fmt, ...) GCC_FMT_ATTR(2, 3);
 void qmp_fd_send_raw(int fd, const char *fmt, ...) GCC_FMT_ATTR(2, 3);
diff --git a/tests/migration-test.c b/tests/migration-test.c
index bd3f5c3125..e0407576cb 100644
--- a/tests/migration-test.c
+++ b/tests/migration-test.c
@@ -174,6 +174,21 @@ static void stop_cb(void *opaque, const char *name, QDict *data)
     }
 }
 
+/*
+ * 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.
  */
@@ -480,6 +495,7 @@ static void migrate(QTestState *who, const char *uri, const char *fmt, ...)
     qdict_put_str(args, "uri", uri);
 
     rsp = qmp("{ 'execute': 'migrate', 'arguments': %p}", args);
+
     g_assert(qdict_haskey(rsp, "return"));
     qobject_unref(rsp);
 }
@@ -1027,6 +1043,90 @@ static void test_precopy_tcp(void)
     g_free(uri);
 }
 
+static void test_migrate_fd_proto(void)
+{
+    QTestState *from, *to;
+    int ret;
+    int pair[2];
+    QDict *rsp;
+    const char *error_desc;
+
+    if (test_migrate_start(&from, &to, "defer", false, false)) {
+        return;
+    }
+
+    /*
+     * We want to pick a speed slow enough that the test completes
+     * quickly, but that it doesn't complete precopy even on a slow
+     * machine, so also set the downtime.
+     */
+    /* 1 ms should make it not converge */
+    migrate_set_parameter(from, "downtime-limit", 1);
+    /* 1GB/s */
+    migrate_set_parameter(from, "max-bandwidth", 1000000000);
+
+    /* Wait for the first serial output from the source */
+    wait_for_serial("src_serial");
+
+    /* Create two connected sockets for migration */
+    ret = socketpair(PF_LOCAL, SOCK_STREAM, 0, pair);
+    g_assert_cmpint(ret, ==, 0);
+
+    /* Send the 1st socket to the target */
+    rsp = wait_command_fd(to, pair[0],
+                          "{ 'execute': 'getfd',"
+                          "  'arguments': { 'fdname': 'fd-mig' }}");
+    qobject_unref(rsp);
+    close(pair[0]);
+
+    /* Start incoming migration from the 1st socket */
+    rsp = wait_command(to, "{ 'execute': 'migrate-incoming',"
+                           "  'arguments': { 'uri': 'fd:fd-mig' }}");
+    qobject_unref(rsp);
+
+    /* Send the 2nd socket to the target */
+    rsp = wait_command_fd(from, pair[1],
+                          "{ 'execute': 'getfd',"
+                          "  'arguments': { 'fdname': 'fd-mig' }}");
+    qobject_unref(rsp);
+    close(pair[1]);
+
+    /* Start migration to the 2nd socket*/
+    migrate(from, "fd:fd-mig", "{}");
+
+    wait_for_migration_pass(from);
+
+    /* 300ms should converge */
+    migrate_set_parameter(from, "downtime-limit", 300);
+
+    if (!got_stop) {
+        qtest_qmp_eventwait(from, "STOP");
+    }
+    qtest_qmp_eventwait(to, "RESUME");
+
+    /* Test closing fds */
+    /* We assume, that QEMU removes named fd from its list,
+     * so this should fail */
+    rsp = qtest_qmp(from, "{ 'execute': 'closefd',"
+                          "  'arguments': { 'fdname': 'fd-mig' }}");
+    g_assert_true(qdict_haskey(rsp, "error"));
+    error_desc = qdict_get_str(qdict_get_qdict(rsp, "error"), "desc");
+    g_assert_cmpstr(error_desc, ==, "File descriptor named 'fd-mig' not found");
+    qobject_unref(rsp);
+
+    rsp = qtest_qmp(to, "{ 'execute': 'closefd',"
+                        "  'arguments': { 'fdname': 'fd-mig' }}");
+    g_assert_true(qdict_haskey(rsp, "error"));
+    error_desc = qdict_get_str(qdict_get_qdict(rsp, "error"), "desc");
+    g_assert_cmpstr(error_desc, ==, "File descriptor named 'fd-mig' not found");
+    qobject_unref(rsp);
+
+    /* Complete migration */
+    wait_for_serial("dest_serial");
+    wait_for_migration_complete(from);
+    test_migrate_end(from, to, true);
+}
+
 int main(int argc, char **argv)
 {
     char template[] = "/tmp/migration-test-XXXXXX";
@@ -1081,6 +1181,7 @@ int main(int argc, char **argv)
     qtest_add_func("/migration/precopy/tcp", test_precopy_tcp);
     /* qtest_add_func("/migration/ignore_shared", test_ignore_shared); */
     qtest_add_func("/migration/xbzrle/unix", test_xbzrle_unix);
+    qtest_add_func("/migration/fd_proto", test_migrate_fd_proto);
 
     ret = g_test_run();
 
-- 
2.21.0

Re: [Qemu-devel] [PATCH v2 0/2] Deferred incoming migration through fd

[Peter Xu]

On Tue, May 28, 2019 at 12:16:31PM +0300, Yury Kotov wrote:
> Hi,
> 
> V2:
> * Revert odd changes in migrate()
> * Add short description for socket_send_fds()
>   and remove ifdef WIN32 as it's not needed
> 
> This series is a continuation of the previous two:
> * migration: Fix handling fd protocol
> * Add 'inline-fd:' protocol for migration
> 
> It's about such use case:
> 1. Target VM: exec ...,-incoming defer
> 2. Target VM: getfd("fd-mig")
> 3. Target VM: migrate-incoming("fd:"fd-mig")
> 4. Source VM: getfd("fd-mig")
> 5. Source VM: migrate("fd-mig")
> 
> Currently, it's not possible to do the step 3, because for incoming migration
> "fd:" protocol expects an integer, not the name of fd.

Reviewed-by: Peter Xu <peterx@redhat.com>

I gave a quick shot on the new test - it runs well.

-- 
Peter Xu