ivshmem: use migration blockers to prevent live migration in peer mode (v2)

Now when you try to migrate with ivshmem, you get a proper QMP error:

(qemu) migrate tcp:localhost:1025
Migration is disabled when using feature 'peer mode' in device 'ivshmem'
(qemu)

Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

hw/ivshmem.c

@@ -18,6 +18,8 @@
 #include "pci.h"
 #include "msix.h"
 #include "kvm.h"
+#include "migration.h"
+#include "qerror.h"
 
 #include <sys/mman.h>
 #include <sys/types.h>
@@ -78,6 +80,8 @@ typedef struct IVShmemState {
     uint32_t features;
     EventfdEntry *eventfd_table;
 
+    Error *migration_blocker;
+
     char * shmobj;
     char * sizearg;
     char * role;
@@ -646,7 +650,8 @@ static int pci_ivshmem_init(PCIDevice *dev)
     }
 
     if (s->role_val == IVSHMEM_PEER) {
-        register_device_unmigratable(&s->dev.qdev, "ivshmem", s);
+        error_set(&s->migration_blocker, QERR_DEVICE_FEATURE_BLOCKS_MIGRATION, "ivshmem", "peer mode");
+        migrate_add_blocker(s->migration_blocker);
     }
 
     pci_conf = s->dev.config;
@@ -741,6 +746,11 @@ static int pci_ivshmem_uninit(PCIDevice *dev)
 {
     IVShmemState *s = DO_UPCAST(IVShmemState, dev, dev);
 
+    if (s->migration_blocker) {
+        migrate_del_blocker(s->migration_blocker);
+        error_free(s->migration_blocker);
+    }
+
     memory_region_destroy(&s->ivshmem_mmio);
     memory_region_del_subregion(&s->bar, &s->ivshmem);
     memory_region_destroy(&s->ivshmem);

qerror.c

@@ -72,6 +72,10 @@ static const QErrorStringTable qerror_table[] = {
         .error_fmt = QERR_DEVICE_IN_USE,
         .desc      = "Device '%(device)' is in use",
     },
+    {
+        .error_fmt = QERR_DEVICE_FEATURE_BLOCKS_MIGRATION,
+        .desc      = "Migration is disabled when using feature '%(feature)' in device '%(device)'",
+    },
     {
         .error_fmt = QERR_DEVICE_LOCKED,
         .desc      = "Device '%(device)' is locked",

qerror.h

@@ -72,6 +72,9 @@ QError *qobject_to_qerror(const QObject *obj);
 #define QERR_DEVICE_IN_USE \
     "{ 'class': 'DeviceInUse', 'data': { 'device': %s } }"
 
+#define QERR_DEVICE_FEATURE_BLOCKS_MIGRATION \
+    "{ 'class': 'DeviceFeatureBlocksMigration', 'data': { 'device': %s, 'feature': %s } }"
+
 #define QERR_DEVICE_LOCKED \
     "{ 'class': 'DeviceLocked', 'data': { 'device': %s } }"
 

savevm.c

@@ -1255,31 +1255,6 @@ void unregister_savevm(DeviceState *dev, const char *idstr, void *opaque)
     }
 }
 
-/* mark a device as not to be migrated, that is the device should be
-   unplugged before migration */
-void register_device_unmigratable(DeviceState *dev, const char *idstr,
-                                                            void *opaque)
-{
-    SaveStateEntry *se;
-    char id[256] = "";
-
-    if (dev && dev->parent_bus && dev->parent_bus->info->get_dev_path) {
-        char *path = dev->parent_bus->info->get_dev_path(dev);
-        if (path) {
-            pstrcpy(id, sizeof(id), path);
-            pstrcat(id, sizeof(id), "/");
-            g_free(path);
-        }
-    }
-    pstrcat(id, sizeof(id), idstr);
-
-    QTAILQ_FOREACH(se, &savevm_handlers, entry) {
-        if (strcmp(se->idstr, id) == 0 && se->opaque == opaque) {
-            se->no_migrate = 1;
-        }
-    }
-}
-
 int vmstate_register_with_alias_id(DeviceState *dev, int instance_id,
                                    const VMStateDescription *vmsd,
                                    void *opaque, int alias_id,