[PATCH v2 11/14] vdpa: Adapt vhost_vdpa_get_vring_base to SVQ

[Eugenio Pérez]

This is needed to achieve migration, so the destination can restore its
index.

Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
---
 hw/virtio/vhost-vdpa.c | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/hw/virtio/vhost-vdpa.c b/hw/virtio/vhost-vdpa.c
index 56f9f125cd..accc4024c2 100644
--- a/hw/virtio/vhost-vdpa.c
+++ b/hw/virtio/vhost-vdpa.c
@@ -1180,8 +1180,25 @@ static int vhost_vdpa_set_vring_base(struct vhost_dev 
*dev,
 static int vhost_vdpa_get_vring_base(struct vhost_dev *dev,
                                        struct vhost_vring_state *ring)
 {
+    struct vhost_vdpa *v = dev->opaque;
     int ret;
 
+    if (v->shadow_vqs_enabled) {
+        VhostShadowVirtqueue *svq = g_ptr_array_index(v->shadow_vqs,
+                                                      ring->index);
+
+        /*
+         * Setting base as last used idx, so destination will see as available
+         * all the entries that the device did not use, including the in-flight
+         * processing ones.
+         *
+         * TODO: This is ok for networking, but other kinds of devices might
+         * have problems with these retransmissions.
+         */
+        ring->num = svq->last_used_idx;
+        return 0;
+    }
+
     ret = vhost_vdpa_call(dev, VHOST_GET_VRING_BASE, ring);
     trace_vhost_vdpa_get_vring_base(dev, ring->index, ring->num);
     return ret;
-- 
2.27.0