Reintroduce migrate-to-exec: support (Charles Duffy)

KVM's live migration support included support for exec: URLs, allowing system
state to be written or received via an arbitrary popen()ed subprocess. This
provides a convenient way to pipe state through a compression algorithm or an
arbitrary network transport on its way to its destination, and a convenient way
to write state to disk; libvirt's qemu driver currently uses migration to exec:
targets for this latter purpose.

This version of the patch refactors now-common code from migrate-tcp.c into
migrate.c. 

Signed-off-by: Charles Duffy <Charles_Duffy@messageone.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>



git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@5694 c046a42c-6fe2-441c-8c8c-71466251a162

1 files changed, 141 insertions, 0 deletions

diff --git a/migration-exec.c b/migration-exec.c
new file mode 100644
index 0000000000..5d0b215fd1
--- /dev/null
+++ b/migration-exec.c
@@ -0,0 +1,141 @@
+/*
+ * QEMU live migration
+ *
+ * Copyright IBM, Corp. 2008
+ * Copyright Dell MessageOne 2008
+ *
+ * Authors:
+ *  Anthony Liguori   <aliguori@us.ibm.com>
+ *  Charles Duffy     <charles_duffy@messageone.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 "qemu-char.h"
+#include "sysemu.h"
+#include "console.h"
+#include "buffered_file.h"
+#include "block.h"
+
+//#define DEBUG_MIGRATION_EXEC
+
+#ifdef DEBUG_MIGRATION_EXEC
+#define dprintf(fmt, ...) \
+    do { printf("migration-exec: " fmt, ## __VA_ARGS__); } while (0)
+#else
+#define dprintf(fmt, ...) \
+    do { } while (0)
+#endif
+
+static int file_errno(FdMigrationState *s)
+{
+    return errno;
+}
+
+static int file_write(FdMigrationState *s, const void * buf, size_t size)
+{
+    return write(s->fd, buf, size);
+}
+
+static int exec_close(FdMigrationState *s)
+{
+    dprintf("exec_close\n");
+    if (s->opaque) {
+        qemu_fclose(s->opaque);
+        s->opaque = NULL;
+        s->fd = -1;
+    }
+    return 0;
+}
+
+MigrationState *exec_start_outgoing_migration(const char *command,
+                                             int64_t bandwidth_limit,
+                                             int async)
+{
+    FdMigrationState *s;
+    FILE *f;
+
+    s = qemu_mallocz(sizeof(*s));
+    if (s == NULL) {
+        dprintf("Unable to allocate FdMigrationState\n");
+        goto err;
+    }
+
+    f = popen(command, "w");
+    if (f == NULL) {
+        dprintf("Unable to popen exec target\n");
+        goto err_after_alloc;
+    }
+
+    s->fd = fileno(f);
+    if (s->fd == -1) {
+        dprintf("Unable to retrieve file descriptor for popen'd handle\n");
+        goto err_after_open;
+    }
+
+    if (fcntl(s->fd, F_SETFD, O_NONBLOCK) == -1) {
+        dprintf("Unable to set nonblocking mode on file descriptor\n");
+        goto err_after_open;
+    }
+
+    s->opaque = qemu_popen(f, "w");
+
+    s->get_error = file_errno;
+    s->write = file_write;
+    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->detach = !async;
+    s->bandwidth_limit = bandwidth_limit;
+
+    if (s->detach == 1) {
+        dprintf("detaching from monitor\n");
+        monitor_suspend();
+        s->detach = 2;
+    }
+
+    migrate_fd_connect(s);
+    return &s->mig_state;
+
+err_after_open:
+    pclose(f);
+err_after_alloc:
+    qemu_free(s);
+err:
+    return NULL;
+}
+
+int exec_start_incoming_migration(const char *command)
+{
+    int ret;
+    QEMUFile *f;
+
+    dprintf("Attempting to start an incoming migration\n");
+    f = qemu_popen_cmd(command, "r");
+    if(f == NULL) {
+        dprintf("Unable to apply qemu wrapper to popen file\n");
+        return -errno;
+    }
+    vm_stop(0); /* just in case */
+    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");
+    vm_start();
+    qemu_fclose(f);
+    return 0;
+
+err:
+    qemu_fclose(f);
+    return -errno;
+}