A vhost device is implicitly preserved across re-exec because its fd is not
closed, and the value of the fd is specified on the command line for the
new qemu to find.  However, new qemu issues an VHOST_RESET_OWNER ioctl,
which fails because the device already has an owner.  To fix, reset the
owner prior to exec.

Signed-off-by: Mark Kanda <mark.kanda@oracle.com>
Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
---
 hw/virtio/vhost.c         | 23 +++++++++++++++++++++++
 include/hw/virtio/vhost.h |  1 +
 2 files changed, 24 insertions(+)

diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
index 8d2a136..bc8df55 100644
--- a/hw/virtio/vhost.c
+++ b/hw/virtio/vhost.c
@@ -23,6 +23,7 @@
 #include "standard-headers/linux/vhost_types.h"
 #include "hw/virtio/virtio-bus.h"
 #include "hw/virtio/virtio-access.h"
+#include "migration/misc.h"
 #include "migration/blocker.h"
 #include "migration/qemu-file-types.h"
 #include "sysemu/dma.h"
@@ -1347,6 +1348,25 @@ static void vhost_virtqueue_cleanup(struct vhost_virtqueue *vq)
     }
 }
 
+static void vhost_cpr_exec_notifier(Notifier *notifier, void *data)
+{
+    MigrationState *s = data;
+    struct vhost_dev *dev;
+    int r;
+
+    if (migrate_mode_of(s) == MIG_MODE_CPR_EXEC) {
+        dev = container_of(notifier, struct vhost_dev, cpr_notifier);
+        if (migration_has_failed(s)) {
+            r = dev->vhost_ops->vhost_set_owner(dev);
+        } else {
+            r = dev->vhost_ops->vhost_reset_device(dev);
+        }
+        if (r < 0) {
+            VHOST_OPS_DEBUG(r, "vhost_reset_device failed");
+        }
+    }
+}
+
 int vhost_dev_init(struct vhost_dev *hdev, void *opaque,
                    VhostBackendType backend_type, uint32_t busyloop_timeout,
                    Error **errp)
@@ -1356,6 +1376,7 @@ int vhost_dev_init(struct vhost_dev *hdev, void *opaque,
 
     hdev->vdev = NULL;
     hdev->migration_blocker = NULL;
+    hdev->cpr_notifier.notify = NULL;
 
     r = vhost_set_backend_type(hdev, backend_type);
     assert(r >= 0);
@@ -1446,6 +1467,7 @@ int vhost_dev_init(struct vhost_dev *hdev, void *opaque,
     hdev->log_enabled = false;
     hdev->started = false;
     memory_listener_register(&hdev->memory_listener, &address_space_memory);
+    migration_add_notifier(&hdev->cpr_notifier, vhost_cpr_exec_notifier);
     QLIST_INSERT_HEAD(&vhost_devices, hdev, entry);
 
     if (used_memslots > hdev->vhost_ops->vhost_backend_memslots_limit(hdev)) {
@@ -1482,6 +1504,7 @@ void vhost_dev_cleanup(struct vhost_dev *hdev)
         QLIST_REMOVE(hdev, entry);
     }
     migrate_del_blocker(&hdev->migration_blocker);
+    migration_remove_notifier(&hdev->cpr_notifier);
     g_free(hdev->mem);
     g_free(hdev->mem_sections);
     if (hdev->vhost_ops) {
diff --git a/include/hw/virtio/vhost.h b/include/hw/virtio/vhost.h
index a346f23..a12c4e1 100644
--- a/include/hw/virtio/vhost.h
+++ b/include/hw/virtio/vhost.h
@@ -101,6 +101,7 @@ struct vhost_dev {
     QLIST_ENTRY(vhost_dev) entry;
     QLIST_HEAD(, vhost_iommu) iommu_list;
     IOMMUNotifier n;
+    Notifier cpr_notifier;
     const VhostDevConfigOps *config_ops;
 };
 
-- 
1.8.3.1