[Qemu-devel] [PATCH v2] add file descriptor migration

[Paolo Bonzini <pbonzini@redhat.com>]

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Cc: Chris Lalancette <clalance@redhat.com>
---
	Change from v1: Chris spotted that I used F_SETFD instead of
	F_SETFL to set non-blocking mode in the outgoing migration
	code.

	Also, now that the migration code is fixed, we tested it with
	various kinds of file descriptors (pipes, UNIX sockets, FIFOs,
	files).

 Makefile       |    2 +-
 hw/hw.h        |    1 +
 migration-fd.c |  137 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 migration.c    |    4 ++
 migration.h    |    7 +++
 savevm.c       |   28 +++++++++++
 6 files changed, 178 insertions(+), 1 deletions(-)
 create mode 100644 migration-fd.c

diff --git a/Makefile b/Makefile
index 5279504..c7ff0be 100644
--- a/Makefile
+++ b/Makefile
@@ -93,7 +93,7 @@ obj-y += qdev.o qdev-properties.o ssi.o
 
 obj-$(CONFIG_BRLAPI) += baum.o
 obj-$(CONFIG_WIN32) += tap-win32.o
-obj-$(CONFIG_POSIX) += migration-exec.o
+obj-$(CONFIG_POSIX) += migration-exec.o migration-fd.o
 
 audio/audio.o audio/fmodaudio.o: QEMU_CFLAGS += $(FMOD_CFLAGS)
 
diff --git a/hw/hw.h b/hw/hw.h
index 322f077..91bf800 100644
--- a/hw/hw.h
+++ b/hw/hw.h
@@ -49,6 +49,7 @@ QEMUFile *qemu_fopen_ops(void *opaque, QEMUFilePutBufferFunc *put_buffer,
                          QEMUFileRateLimit *rate_limit,
                          QEMUFileSetRateLimit *set_rate_limit);
 QEMUFile *qemu_fopen(const char *filename, const char *mode);
+QEMUFile *qemu_fdopen(int fd, const char *mode);
 QEMUFile *qemu_fopen_socket(int fd);
 QEMUFile *qemu_popen(FILE *popen_file, const char *mode);
 QEMUFile *qemu_popen_cmd(const char *command, const char *mode);
diff --git a/migration-fd.c b/migration-fd.c
new file mode 100644
index 0000000..794c2ac
--- /dev/null
+++ b/migration-fd.c
@@ -0,0 +1,137 @@
+/*
+ * QEMU live migration via generic fd
+ *
+ * Copyright Red Hat, Inc. 2009
+ *
+ * Authors:
+ *  Chris Lalancette <clalance@redhat.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2.  See
+ * the COPYING file in the top-level directory.
+ *
+ */
+
+#include "qemu-common.h"
+#include "qemu_socket.h"
+#include "migration.h"
+#include "monitor.h"
+#include "qemu-char.h"
+#include "sysemu.h"
+#include "buffered_file.h"
+#include "block.h"
+#include "qemu_socket.h"
+
+//#define DEBUG_MIGRATION_FD
+
+#ifdef DEBUG_MIGRATION_FD
+#define dprintf(fmt, ...) \
+    do { printf("migration-fd: " fmt, ## __VA_ARGS__); } while (0)
+#else
+#define dprintf(fmt, ...) \
+    do { } while (0)
+#endif
+
+static int fd_errno(FdMigrationState *s)
+{
+    return errno;
+}
+
+static int fd_write(FdMigrationState *s, const void * buf, size_t size)
+{
+    return write(s->fd, buf, size);
+}
+
+static int fd_close(FdMigrationState *s)
+{
+    dprintf("fd_close\n");
+    if (s->fd != -1) {
+        close(s->fd);
+        s->fd = -1;
+    }
+    return 0;
+}
+
+MigrationState *fd_start_outgoing_migration(Monitor *mon,
+					    const char *fdname,
+					    int64_t bandwidth_limit,
+					    int detach)
+{
+    FdMigrationState *s;
+
+    s = qemu_mallocz(sizeof(*s));
+
+    s->fd = monitor_get_fd(mon, fdname);
+    if (s->fd == -1) {
+        dprintf("fd_migration: invalid file descriptor identifier\n");
+        goto err_after_alloc;
+    }
+
+    if (fcntl(s->fd, F_SETFL, O_NONBLOCK) == -1) {
+        dprintf("Unable to set nonblocking mode on file descriptor\n");
+        goto err_after_open;
+    }
+
+    s->get_error = fd_errno;
+    s->write = fd_write;
+    s->close = fd_close;
+    s->mig_state.cancel = migrate_fd_cancel;
+    s->mig_state.get_status = migrate_fd_get_status;
+    s->mig_state.release = migrate_fd_release;
+
+    s->state = MIG_STATE_ACTIVE;
+    s->mon_resume = NULL;
+    s->bandwidth_limit = bandwidth_limit;
+
+    if (!detach)
+        migrate_fd_monitor_suspend(s);
+
+    migrate_fd_connect(s);
+    return &s->mig_state;
+
+err_after_open:
+    close(s->fd);
+err_after_alloc:
+    qemu_free(s);
+    return NULL;
+}
+
+static void fd_accept_incoming_migration(void *opaque)
+{
+    QEMUFile *f = opaque;
+    int ret;
+
+    ret = qemu_loadvm_state(f);
+    if (ret < 0) {
+        fprintf(stderr, "load of migration failed\n");
+        goto err;
+    }
+    qemu_announce_self();
+    dprintf("successfully loaded vm state\n");
+    /* we've successfully migrated, close the fd */
+    qemu_set_fd_handler2(qemu_stdio_fd(f), NULL, NULL, NULL, NULL);
+    if (autostart)
+        vm_start();
+
+err:
+    qemu_fclose(f);
+}
+
+int fd_start_incoming_migration(const char *infd)
+{
+    int fd;
+    QEMUFile *f;
+
+    dprintf("Attempting to start an incoming migration via fd\n");
+
+    fd = strtol(infd, NULL, 0);
+    f = qemu_fdopen(fd, "rb");
+    if(f == NULL) {
+        dprintf("Unable to apply qemu wrapper to file descriptor\n");
+        return -errno;
+    }
+
+    qemu_set_fd_handler2(fd, NULL, fd_accept_incoming_migration, NULL,
+			 (void *)(unsigned long)f);
+
+    return 0;
+}
diff --git a/migration.c b/migration.c
index ee64d41..0ca4399 100644
--- a/migration.c
+++ b/migration.c
@@ -43,6 +43,8 @@ void qemu_start_incoming_migration(const char *uri)
 #if !defined(WIN32)
     else if (strstart(uri, "exec:", &p))
         exec_start_incoming_migration(p);
+    else if (strstart(uri, "fd:", &p))
+        fd_start_incoming_migration(p);
 #endif
     else
         fprintf(stderr, "unknown migration protocol: %s\n", uri);
@@ -58,6 +60,8 @@ void do_migrate(Monitor *mon, int detach, const char *uri)
 #if !defined(WIN32)
     else if (strstart(uri, "exec:", &p))
         s = exec_start_outgoing_migration(p, max_throttle, detach);
+    else if (strstart(uri, "fd:", &p))
+        s = fd_start_outgoing_migration(mon, p, max_throttle, detach);
 #endif
     else
         monitor_printf(mon, "unknown migration protocol: %s\n", uri);
diff --git a/migration.h b/migration.h
index 37c7f8e..5033d02 100644
--- a/migration.h
+++ b/migration.h
@@ -73,6 +73,13 @@ MigrationState *tcp_start_outgoing_migration(const char *host_port,
 					     int64_t bandwidth_limit,
 					     int detach);
 
+int fd_start_incoming_migration(const char *path);
+
+MigrationState *fd_start_outgoing_migration(Monitor *mon,
+					    const char *fdname,
+					    int64_t bandwidth_limit,
+					    int detach);
+
 void migrate_fd_monitor_suspend(FdMigrationState *s);
 
 void migrate_fd_error(FdMigrationState *s);
diff --git a/savevm.c b/savevm.c
index 975e7ab..4575653 100644
--- a/savevm.c
+++ b/savevm.c
@@ -285,6 +285,34 @@ int qemu_stdio_fd(QEMUFile *f)
     return fd;
 }
 
+QEMUFile *qemu_fdopen(int fd, const char *mode)
+{
+    QEMUFileStdio *s;
+
+    if (mode == NULL ||
+	(mode[0] != 'r' && mode[0] != 'w') ||
+	mode[1] != 'b' || mode[2] != 0) {
+        fprintf(stderr, "qemu_fdopen: Argument validity check failed\n");
+        return NULL;
+    }
+
+    s = qemu_mallocz(sizeof(QEMUFileStdio));
+    s->stdio_file = fdopen(fd, mode);
+    if (!s->stdio_file)
+        goto fail;
+
+    if(mode[0] == 'r') {
+        s->file = qemu_fopen_ops(s, NULL, stdio_get_buffer, stdio_fclose, NULL, NULL);
+    } else {
+        s->file = qemu_fopen_ops(s, stdio_put_buffer, NULL, stdio_fclose, NULL, NULL);
+    }
+    return s->file;
+
+fail:
+    qemu_free(s);
+    return NULL;
+}
+
 QEMUFile *qemu_fopen_socket(int fd)
 {
     QEMUFileSocket *s = qemu_mallocz(sizeof(QEMUFileSocket));
-- 
1.6.2.5