[RFC,v1,4/4] vhost: introduce vhost_set_vring_ready method

diff --git a/hw/net/vhost_net-stub.c b/hw/net/vhost_net-stub.c
index aac0e98228..f5ef1e3055 100644
--- a/hw/net/vhost_net-stub.c
+++ b/hw/net/vhost_net-stub.c
@@ -86,6 +86,11 @@  int vhost_set_vring_enable(NetClientState *nc, int enable)
     return 0;
 }
 
+int vhost_set_vring_ready(NetClientState *nc)
+{
+    return 0;
+}
+
 int vhost_net_set_mtu(struct vhost_net *net, uint16_t mtu)
 {
     return 0;
diff --git a/hw/net/vhost_net.c b/hw/net/vhost_net.c
index 0d13fda2fc..463e333531 100644
--- a/hw/net/vhost_net.c
+++ b/hw/net/vhost_net.c
@@ -380,6 +380,10 @@  int vhost_net_start(VirtIODevice *dev, NetClientState *ncs,
                 goto err_start;
             }
         }
+
+        if (virtio_queue_enabled(dev, i)) {
+            vhost_set_vring_ready(peer);
+        }
     }
 
     return 0;
@@ -487,6 +491,18 @@  int vhost_set_vring_enable(NetClientState *nc, int enable)
     return 0;
 }
 
+int vhost_set_vring_ready(NetClientState *nc)
+{
+    VHostNetState *net = get_vhost_net(nc);
+    const VhostOps *vhost_ops = net->dev.vhost_ops;
+
+    if (vhost_ops && vhost_ops->vhost_set_vring_ready) {
+        return vhost_ops->vhost_set_vring_ready(&net->dev);
+    }
+
+    return 0;
+}
+
 int vhost_net_set_mtu(struct vhost_net *net, uint16_t mtu)
 {
     const VhostOps *vhost_ops = net->dev.vhost_ops;
diff --git a/hw/virtio/vhost-vdpa.c b/hw/virtio/vhost-vdpa.c
index 213b327600..49224ef9f8 100644
--- a/hw/virtio/vhost-vdpa.c
+++ b/hw/virtio/vhost-vdpa.c
@@ -325,18 +325,15 @@  static int vhost_vdpa_get_vq_index(struct vhost_dev *dev, int idx)
     return idx - dev->vq_index;
 }
 
-static int vhost_vdpa_set_vring_enable(struct vhost_dev *dev, int enable)
+static int vhost_vdpa_set_vring_ready(struct vhost_dev *dev)
 {
     int i;
 
     for (i = 0; i < dev->nvqs; ++i) {
         struct vhost_vring_state state = {
             .index = dev->vq_index + i,
-            .num   = enable,
+            .num = 1,
         };
-
-        state.num = 1;
-
         vhost_vdpa_call(dev, VHOST_VDPA_SET_VRING_ENABLE, &state);
     }
 
@@ -368,7 +365,7 @@  const VhostOps vdpa_ops = {
         .vhost_set_owner = vhost_vdpa_set_owner,
         .vhost_reset_device = vhost_vdpa_reset_device,
         .vhost_get_vq_index = vhost_vdpa_get_vq_index,
-        .vhost_set_vring_enable = vhost_vdpa_set_vring_enable,
+        .vhost_set_vring_ready = vhost_vdpa_set_vring_ready,
         .vhost_requires_shm_log = NULL,
         .vhost_migration_done = NULL,
         .vhost_backend_can_merge = NULL,
diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
index c6b47a9c73..4aaf5d953e 100644
--- a/hw/virtio/virtio-pci.c
+++ b/hw/virtio/virtio-pci.c
@@ -1103,6 +1103,18 @@  static AddressSpace *virtio_pci_get_dma_as(DeviceState *d)
     return pci_get_address_space(dev);
 }
 
+static bool virtio_pci_queue_enabled(DeviceState *d, int n)
+{
+    VirtIOPCIProxy *proxy = VIRTIO_PCI(d);
+    VirtIODevice *vdev = virtio_bus_get_device(&proxy->bus);
+
+    if (virtio_vdev_has_feature(vdev, VIRTIO_F_VERSION_1)) {
+        return proxy->vqs[vdev->queue_sel].enabled;
+    }
+
+    return virtio_queue_get_desc_addr(vdev, n) != 0;
+}
+
 static int virtio_pci_add_mem_cap(VirtIOPCIProxy *proxy,
                                    struct virtio_pci_cap *cap)
 {
@@ -2053,6 +2065,7 @@  static void virtio_pci_bus_class_init(ObjectClass *klass, void *data)
     k->ioeventfd_enabled = virtio_pci_ioeventfd_enabled;
     k->ioeventfd_assign = virtio_pci_ioeventfd_assign;
     k->get_dma_as = virtio_pci_get_dma_as;
+    k->queue_enabled = virtio_pci_queue_enabled;
 }
 
 static const TypeInfo virtio_pci_bus_info = {
diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index 04716b5f6c..09732a8836 100644
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -3169,6 +3169,12 @@  hwaddr virtio_queue_get_desc_addr(VirtIODevice *vdev, int n)
 
 bool virtio_queue_enabled(VirtIODevice *vdev, int n)
 {
+    BusState *qbus = qdev_get_parent_bus(DEVICE(vdev));
+    VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
+
+    if (k->queue_enabled)
+        return k->queue_enabled(qbus->parent, n);
+
     return virtio_queue_get_desc_addr(vdev, n) != 0;
 }
 
diff --git a/include/hw/virtio/vhost-backend.h b/include/hw/virtio/vhost-backend.h
index d81bd9885f..ce8de6d308 100644
--- a/include/hw/virtio/vhost-backend.h
+++ b/include/hw/virtio/vhost-backend.h
@@ -78,6 +78,7 @@  typedef int (*vhost_reset_device_op)(struct vhost_dev *dev);
 typedef int (*vhost_get_vq_index_op)(struct vhost_dev *dev, int idx);
 typedef int (*vhost_set_vring_enable_op)(struct vhost_dev *dev,
                                          int enable);
+typedef int (*vhost_set_vring_ready_op)(struct vhost_dev *dev);
 typedef bool (*vhost_requires_shm_log_op)(struct vhost_dev *dev);
 typedef int (*vhost_migration_done_op)(struct vhost_dev *dev,
                                        char *mac_addr);
@@ -140,6 +141,7 @@  typedef struct VhostOps {
     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;
+    vhost_set_vring_ready_op vhost_set_vring_ready;
     vhost_requires_shm_log_op vhost_requires_shm_log;
     vhost_migration_done_op vhost_migration_done;
     vhost_backend_can_merge_op vhost_backend_can_merge;
diff --git a/include/hw/virtio/virtio-bus.h b/include/hw/virtio/virtio-bus.h
index 38c9399cd4..0f6f215925 100644
--- a/include/hw/virtio/virtio-bus.h
+++ b/include/hw/virtio/virtio-bus.h
@@ -83,6 +83,10 @@  typedef struct VirtioBusClass {
      */
     int (*ioeventfd_assign)(DeviceState *d, EventNotifier *notifier,
                             int n, bool assign);
+    /*
+     * Whether queue number n is enabled.
+     */
+    bool (*queue_enabled)(DeviceState *d, int n);
     /*
      * Does the transport have variable vring alignment?
      * (ie can it ever call virtio_queue_set_align()?)
diff --git a/include/net/vhost_net.h b/include/net/vhost_net.h
index 6f3a624cf7..db473ff4d2 100644
--- a/include/net/vhost_net.h
+++ b/include/net/vhost_net.h
@@ -35,6 +35,7 @@  int vhost_net_notify_migration_done(VHostNetState *net, char* mac_addr);
 VHostNetState *get_vhost_net(NetClientState *nc);
 
 int vhost_set_vring_enable(NetClientState * nc, int enable);
+int vhost_set_vring_ready(NetClientState * nc);
 
 uint64_t vhost_net_get_acked_features(VHostNetState *net);