1 files changed, 70 insertions, 1 deletions

diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index 0000a7b41c..397c261c3c 100644
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -1023,6 +1023,73 @@ static void virtqueue_packed_flush(VirtQueue *vq, unsigned int count)
     }
 }
 
+static void virtqueue_ordered_flush(VirtQueue *vq)
+{
+    unsigned int i = vq->used_idx % vq->vring.num;
+    unsigned int ndescs = 0;
+    uint16_t old = vq->used_idx;
+    uint16_t new;
+    bool packed;
+    VRingUsedElem uelem;
+
+    packed = virtio_vdev_has_feature(vq->vdev, VIRTIO_F_RING_PACKED);
+
+    if (packed) {
+        if (unlikely(!vq->vring.desc)) {
+            return;
+        }
+    } else if (unlikely(!vq->vring.used)) {
+        return;
+    }
+
+    /* First expected in-order element isn't ready, nothing to do */
+    if (!vq->used_elems[i].in_order_filled) {
+        return;
+    }
+
+    /* Search for filled elements in-order */
+    while (vq->used_elems[i].in_order_filled) {
+        /*
+         * First entry for packed VQs is written last so the guest
+         * doesn't see invalid descriptors.
+         */
+        if (packed && i != vq->used_idx) {
+            virtqueue_packed_fill_desc(vq, &vq->used_elems[i], ndescs, false);
+        } else if (!packed) {
+            uelem.id = vq->used_elems[i].index;
+            uelem.len = vq->used_elems[i].len;
+            vring_used_write(vq, &uelem, i);
+        }
+
+        vq->used_elems[i].in_order_filled = false;
+        ndescs += vq->used_elems[i].ndescs;
+        i += vq->used_elems[i].ndescs;
+        if (i >= vq->vring.num) {
+            i -= vq->vring.num;
+        }
+    }
+
+    if (packed) {
+        virtqueue_packed_fill_desc(vq, &vq->used_elems[vq->used_idx], 0, true);
+        vq->used_idx += ndescs;
+        if (vq->used_idx >= vq->vring.num) {
+            vq->used_idx -= vq->vring.num;
+            vq->used_wrap_counter ^= 1;
+            vq->signalled_used_valid = false;
+        }
+    } else {
+        /* Make sure buffer is written before we update index. */
+        smp_wmb();
+        new = old + ndescs;
+        vring_used_idx_set(vq, new);
+        if (unlikely((int16_t)(new - vq->signalled_used) <
+                     (uint16_t)(new - old))) {
+            vq->signalled_used_valid = false;
+        }
+    }
+    vq->inuse -= ndescs;
+}
+
 void virtqueue_flush(VirtQueue *vq, unsigned int count)
 {
     if (virtio_device_disabled(vq->vdev)) {
@@ -1030,7 +1097,9 @@ void virtqueue_flush(VirtQueue *vq, unsigned int count)
         return;
     }
 
-    if (virtio_vdev_has_feature(vq->vdev, VIRTIO_F_RING_PACKED)) {
+    if (virtio_vdev_has_feature(vq->vdev, VIRTIO_F_IN_ORDER)) {
+        virtqueue_ordered_flush(vq);
+    } else if (virtio_vdev_has_feature(vq->vdev, VIRTIO_F_RING_PACKED)) {
         virtqueue_packed_flush(vq, count);
     } else {
         virtqueue_split_flush(vq, count);