From: Steve Sistare <steven.sistare@oracle.com>

When preserving a vhost fd using CPR, call VHOST_RESET_OWNER prior to CPR
in old QEMU.  Otherwise, new QEMU will fail when it calls VHOST_SET_OWNER
during vhost_dev_init.

Signed-off-by: Mark Kanda <mark.kanda@oracle.com>
Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
Signed-off-by: Ben Chaney <bchaney@akamai.com>
---
 hw/virtio/vhost-backend.c         |  6 ++++++
 hw/virtio/vhost.c                 | 32 ++++++++++++++++++++++++++++++++
 include/hw/virtio/vhost-backend.h |  1 +
 include/hw/virtio/vhost.h         |  1 +
 4 files changed, 40 insertions(+)

diff --git a/hw/virtio/vhost-backend.c b/hw/virtio/vhost-backend.c
index 4367db0d95..1447d12963 100644
--- a/hw/virtio/vhost-backend.c
+++ b/hw/virtio/vhost-backend.c
@@ -261,6 +261,11 @@ static int vhost_kernel_set_owner(struct vhost_dev *dev)
     return vhost_kernel_call(dev, VHOST_SET_OWNER, NULL);
 }
 
+static int vhost_kernel_reset_owner(struct vhost_dev *dev)
+{
+    return vhost_kernel_call(dev, VHOST_RESET_OWNER, NULL);
+}
+
 static int vhost_kernel_get_vq_index(struct vhost_dev *dev, int idx)
 {
     assert(idx >= dev->vq_index && idx < dev->vq_index + dev->nvqs);
@@ -385,6 +390,7 @@ const VhostOps kernel_ops = {
         .vhost_get_features_ex = vhost_kernel_get_features,
         .vhost_set_backend_cap = vhost_kernel_set_backend_cap,
         .vhost_set_owner = vhost_kernel_set_owner,
+        .vhost_reset_owner = vhost_kernel_reset_owner,
         .vhost_get_vq_index = vhost_kernel_get_vq_index,
         .vhost_vsock_set_guest_cid = vhost_kernel_vsock_set_guest_cid,
         .vhost_vsock_set_running = vhost_kernel_vsock_set_running,
diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
index 266a11514a..011d73dae2 100644
--- a/hw/virtio/vhost.c
+++ b/hw/virtio/vhost.c
@@ -24,6 +24,7 @@
 #include "standard-headers/linux/vhost_types.h"
 #include "hw/virtio/virtio-bus.h"
 #include "hw/mem/memory-device.h"
+#include "migration/misc.h"
 #include "migration/blocker.h"
 #include "migration/qemu-file-types.h"
 #include "system/dma.h"
@@ -1540,6 +1541,32 @@ static int vhost_dev_get_features(struct vhost_dev *hdev,
     return r;
 }
 
+static int vhost_cpr_notifier(NotifierWithReturn *notifier,
+                              MigrationEvent *e, Error **errp)
+{
+    struct vhost_dev *dev;
+    int r;
+
+    dev = container_of(notifier, struct vhost_dev, cpr_transfer_notifier);
+
+    if (dev->vhost_ops->backend_type != VHOST_BACKEND_TYPE_KERNEL) {
+        return 0;
+    }
+
+    if (e->type == MIG_EVENT_PRECOPY_SETUP) {
+        r = dev->vhost_ops->vhost_reset_owner(dev);
+        if (r < 0) {
+            VHOST_OPS_DEBUG(r, "vhost_reset_owner failed");
+        }
+    } else if (e->type == MIG_EVENT_PRECOPY_FAILED) {
+        r = dev->vhost_ops->vhost_set_owner(dev);
+        if (r < 0) {
+            VHOST_OPS_DEBUG(r, "vhost_set_owner failed");
+        }
+    }
+    return 0;
+}
+
 int vhost_dev_init(struct vhost_dev *hdev, void *opaque,
                    VhostBackendType backend_type, uint32_t busyloop_timeout,
                    Error **errp)
@@ -1550,6 +1577,7 @@ int vhost_dev_init(struct vhost_dev *hdev, void *opaque,
 
     hdev->vdev = NULL;
     hdev->migration_blocker = NULL;
+    hdev->cpr_transfer_notifier.notify = NULL;
 
     r = vhost_set_backend_type(hdev, backend_type);
     assert(r >= 0);
@@ -1650,6 +1678,9 @@ 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_mode(&hdev->cpr_transfer_notifier,
+                                vhost_cpr_notifier,
+                                MIG_MODE_CPR_TRANSFER);
     QLIST_INSERT_HEAD(&vhost_devices, hdev, entry);
 
     /*
@@ -1702,6 +1733,7 @@ void vhost_dev_cleanup(struct vhost_dev *hdev)
         QLIST_REMOVE(hdev, entry);
     }
     migrate_del_blocker(&hdev->migration_blocker);
+    migration_remove_notifier(&hdev->cpr_transfer_notifier);
     g_free(hdev->mem);
     g_free(hdev->mem_sections);
     if (hdev->vhost_ops) {
diff --git a/include/hw/virtio/vhost-backend.h b/include/hw/virtio/vhost-backend.h
index ff94fa1734..18ce5ea9a0 100644
--- a/include/hw/virtio/vhost-backend.h
+++ b/include/hw/virtio/vhost-backend.h
@@ -196,6 +196,7 @@ typedef struct VhostOps {
     vhost_get_features_op vhost_get_features;
     vhost_set_backend_cap_op vhost_set_backend_cap;
     vhost_set_owner_op vhost_set_owner;
+    vhost_set_owner_op vhost_reset_owner;
     vhost_reset_device_op vhost_reset_device;
     vhost_get_vq_index_op vhost_get_vq_index;
     vhost_set_vring_enable_op vhost_set_vring_enable;
diff --git a/include/hw/virtio/vhost.h b/include/hw/virtio/vhost.h
index 08bbb4dfe9..5d11a97e43 100644
--- a/include/hw/virtio/vhost.h
+++ b/include/hw/virtio/vhost.h
@@ -133,6 +133,7 @@ struct vhost_dev {
     QLIST_ENTRY(vhost_dev) logdev_entry;
     QLIST_HEAD(, vhost_iommu) iommu_list;
     IOMMUNotifier n;
+    NotifierWithReturn cpr_transfer_notifier;
     const VhostDevConfigOps *config_ops;
 };
 

-- 
2.34.1