vfio: allow cpr-reboot migration if suspended

Allow cpr-reboot for vfio if the guest is in the suspended runstate.  The
guest drivers' suspend methods flush outstanding requests and re-initialize
the devices, and thus there is no device state to save and restore.  The
user is responsible for suspending the guest before initiating cpr, such as
by issuing guest-suspend-ram to the qemu guest agent.

Relax the vfio blocker so it does not apply to cpr, and add a notifier that
verifies the guest is suspended.

Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
Reviewed-by: Cédric Le Goater <clg@redhat.com>

hw/vfio/common.c

@@ -128,7 +128,7 @@ int vfio_block_multiple_devices_migration(VFIODevice *vbasedev, Error **errp)
     error_setg(&multiple_devices_migration_blocker,
                "Multiple VFIO devices migration is supported only if all of "
                "them support P2P migration");
-    ret = migrate_add_blocker(&multiple_devices_migration_blocker, errp);
+    ret = migrate_add_blocker_normal(&multiple_devices_migration_blocker, errp);
 
     return ret;
 }

hw/vfio/cpr.c

@@ -7,13 +7,33 @@
 
 #include "qemu/osdep.h"
 #include "hw/vfio/vfio-common.h"
+#include "migration/misc.h"
 #include "qapi/error.h"
+#include "sysemu/runstate.h"
+
+static int vfio_cpr_reboot_notifier(NotifierWithReturn *notifier,
+                                    MigrationEvent *e, Error **errp)
+{
+    if (e->type == MIG_EVENT_PRECOPY_SETUP &&
+        !runstate_check(RUN_STATE_SUSPENDED) && !vm_get_suspended()) {
+
+        error_setg(errp,
+            "VFIO device only supports cpr-reboot for runstate suspended");
+
+        return -1;
+    }
+    return 0;
+}
 
 int vfio_cpr_register_container(VFIOContainerBase *bcontainer, Error **errp)
 {
+    migration_add_notifier_mode(&bcontainer->cpr_reboot_notifier,
+                                vfio_cpr_reboot_notifier,
+                                MIG_MODE_CPR_REBOOT);
     return 0;
 }
 
 void vfio_cpr_unregister_container(VFIOContainerBase *bcontainer)
 {
+    migration_remove_notifier(&bcontainer->cpr_reboot_notifier);
 }

hw/vfio/migration.c

@@ -889,7 +889,7 @@ static int vfio_block_migration(VFIODevice *vbasedev, Error *err, Error **errp)
     vbasedev->migration_blocker = error_copy(err);
     error_free(err);
 
-    return migrate_add_blocker(&vbasedev->migration_blocker, errp);
+    return migrate_add_blocker_normal(&vbasedev->migration_blocker, errp);
 }
 
 /* ---------------------------------------------------------------------- */

include/hw/vfio/vfio-container-base.h

@@ -49,6 +49,7 @@ typedef struct VFIOContainerBase {
     QLIST_ENTRY(VFIOContainerBase) next;
     QLIST_HEAD(, VFIODevice) device_list;
     GList *iova_ranges;
+    NotifierWithReturn cpr_reboot_notifier;
 } VFIOContainerBase;
 
 typedef struct VFIOGuestIOMMU {