[PATCH v1 1/2] virtio: struct VirtQueue introduce reset

[Xuan Zhuo <xuanzhuo@linux.alibaba.com>]

In the current design, we stop the device from operating on the vring
during per-queue reset by resetting the structure VirtQueue.

But before the reset operation, when recycling some resources, we should
stop referencing new vring resources. For example, when recycling
virtio-net's asynchronous sending resources, virtio-net should be able
to perceive that the current queue is in the per-queue reset state, and
stop sending new packets from the tx queue.

Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
---
 hw/virtio/virtio.c         | 15 +++++++++++++++
 include/hw/virtio/virtio.h |  1 +
 2 files changed, 16 insertions(+)

diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index f35178f5fc..c954f2a2b3 100644
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -142,6 +142,8 @@ struct VirtQueue
     /* Notification enabled? */
     bool notification;
 
+    bool disabled_by_reset;
+
     uint16_t queue_index;
 
     unsigned int inuse;
@@ -2079,6 +2081,12 @@ void virtio_queue_reset(VirtIODevice *vdev, uint32_t queue_index)
 {
     VirtioDeviceClass *k = VIRTIO_DEVICE_GET_CLASS(vdev);
 
+    /*
+     * Mark this queue is per-queue reset status. The device should release the
+     * references of the vring, and not refer more new vring item.
+     */
+    vdev->vq[queue_index].disabled_by_reset = true;
+
     if (k->queue_reset) {
         k->queue_reset(vdev, queue_index);
     }
@@ -2102,11 +2110,18 @@ void virtio_queue_enable(VirtIODevice *vdev, uint32_t queue_index)
     }
     */
 
+    vdev->vq[queue_index].disabled_by_reset = false;
+
     if (k->queue_enable) {
         k->queue_enable(vdev, queue_index);
     }
 }
 
+bool virtio_queue_reset_state(VirtQueue *vq)
+{
+    return vq->disabled_by_reset;
+}
+
 void virtio_reset(void *opaque)
 {
     VirtIODevice *vdev = opaque;
diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h
index 77c6c55929..00e91af7c4 100644
--- a/include/hw/virtio/virtio.h
+++ b/include/hw/virtio/virtio.h
@@ -319,6 +319,7 @@ int virtio_set_status(VirtIODevice *vdev, uint8_t val);
 void virtio_reset(void *opaque);
 void virtio_queue_reset(VirtIODevice *vdev, uint32_t queue_index);
 void virtio_queue_enable(VirtIODevice *vdev, uint32_t queue_index);
+bool virtio_queue_reset_state(VirtQueue *vq);
 void virtio_update_irq(VirtIODevice *vdev);
 int virtio_set_features(VirtIODevice *vdev, uint64_t val);
 
-- 
2.32.0.3.g01195cf9f