Allow monitor interaction when using migrate -exec

All,
     I've recently been playing around with migration via exec.  Unfortunately,
when starting the incoming qemu process with "-incoming exec:cmd", it suffers
the same problem that -incoming tcp used to suffer; namely, that you can't
interact with the monitor until after the migration has happened.  This causes
problems for libvirt usage of -incoming exec, since libvirt expects to be able
to access the monitor ahead of time.  This fairly simple patch allows you to
access the monitor both before and after the migration has completed using exec.

(note: developed/tested with qemu-kvm, but applies perfectly fine to qemu)

Signed-off-by: Chris Lalancette <clalance@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

diff --git a/hw/hw.h b/hw/hw.h
index a3f5717b3e30f92512b221ad7953e622330cc878..c83580073cf7b71eec4d6529e82ab0f79a9140a5 100644 (file)
--- a/hw/hw.h
+++ b/hw/hw.h
@@ -51,6 +51,7 @@ QEMUFile *qemu_fopen(const char *filename, 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);
+int qemu_popen_fd(QEMUFile *f);
 void qemu_fflush(QEMUFile *f);
 int qemu_fclose(QEMUFile *f);
 void qemu_put_buffer(QEMUFile *f, const uint8_t *buf, int size);

diff --git a/migration-exec.c b/migration-exec.c
index f0869a1146e6f42d357f1a505fe854507d5eeb6e..0dd5aff315c24b207e6c8dc22c2eba036fb02075 100644 (file)
--- a/migration-exec.c
+++ b/migration-exec.c
@@ -104,17 +104,11 @@ err_after_alloc:
     return NULL;
 }
 
-int exec_start_incoming_migration(const char *command)
+static void exec_accept_incoming_migration(void *opaque)
 {
+    QEMUFile *f = opaque;
     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) {
@@ -123,11 +117,28 @@ int exec_start_incoming_migration(const char *command)
     }
     qemu_announce_self();
     dprintf("successfully loaded vm state\n");
+    /* we've successfully migrated, close the fd */
+    qemu_set_fd_handler2(qemu_popen_fd(f), NULL, NULL, NULL, NULL);
     vm_start();
-    qemu_fclose(f);
-    return 0;
 
 err:
     qemu_fclose(f);
-    return -errno;
+}
+
+int exec_start_incoming_migration(const char *command)
+{
+    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;
+    }
+
+    qemu_set_fd_handler2(qemu_popen_fd(f), NULL,
+                        exec_accept_incoming_migration, NULL,
+                        (void *)(unsigned long)f);
+
+    return 0;
 }

diff --git a/savevm.c b/savevm.c
index 68ffd03e6e4d8d4e37ba1004bc6c36bc80657ba2..248aea3edfa1cd1ff32197db94b355273594a9bf 100644 (file)
--- a/savevm.c
+++ b/savevm.c
@@ -244,7 +244,6 @@ QEMUFile *qemu_popen(FILE *popen_file, const char *mode)
     } else {
         s->file = qemu_fopen_ops(s, popen_put_buffer, NULL, popen_close, NULL, NULL);
     }
-    fprintf(stderr, "qemu_popen: returning result of qemu_fopen_ops\n");
     return s->file;
 }
 
@@ -260,6 +259,17 @@ QEMUFile *qemu_popen_cmd(const char *command, const char *mode)
     return qemu_popen(popen_file, mode);
 }
 
+int qemu_popen_fd(QEMUFile *f)
+{
+    QEMUFilePopen *p;
+    int fd;
+
+    p = (QEMUFilePopen *)f->opaque;
+    fd = fileno(p->popen_file);
+
+    return fd;
+}
+
 QEMUFile *qemu_fopen_socket(int fd)
 {
     QEMUFileSocket *s = qemu_mallocz(sizeof(QEMUFileSocket));