[PATCH v3 12/14] vdpa: block migration if dev does not have _F_SUSPEND

[Eugenio Pérez]

Next patches enable devices to be migrated even if vdpa netdev has not
been started with x-svq. However, not all devices are migratable, so we
need to block migration if we detect that.

Block vhost-vdpa device migration if it does not offer _F_SUSPEND and it
has not been started with x-svq.

Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
---
 hw/virtio/vhost-vdpa.c | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/hw/virtio/vhost-vdpa.c b/hw/virtio/vhost-vdpa.c
index 52c72e7c94..3a85f9f1ed 100644
--- a/hw/virtio/vhost-vdpa.c
+++ b/hw/virtio/vhost-vdpa.c
@@ -443,6 +443,27 @@ static int vhost_vdpa_init(struct vhost_dev *dev, void 
*opaque, Error **errp)
         return 0;
     }
 
+    /*
+     * If dev->shadow_vqs_enabled at initialization that means the device has
+     * been started with x-svq=on, so don't block migration
+     */
+    if (dev->migration_blocker == NULL && !v->shadow_vqs_enabled) {
+        uint64_t backend_features;
+
+        /* We don't have dev->backend_features yet */
+        ret = vhost_vdpa_call(dev, VHOST_GET_BACKEND_FEATURES,
+                              &backend_features);
+        if (unlikely(ret)) {
+            error_setg_errno(errp, -ret, "Could not get backend features");
+            return ret;
+        }
+
+        if (!(backend_features & BIT_ULL(VHOST_BACKEND_F_SUSPEND))) {
+            error_setg(&dev->migration_blocker,
+                "vhost-vdpa backend lacks VHOST_BACKEND_F_SUSPEND feature.");
+        }
+    }
+
     /*
      * Similar to VFIO, we end up pinning all guest memory and have to
      * disable discarding of RAM.
-- 
2.31.1