[RFC PATCH for 8.0 01/13] vhost: add available descriptor list in SVQ

["Eugenio Pérez" <eperezma@redhat.com>]

This helps to track the inflight buffers, make easier to transverse all
of them, and return them in order.

Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
---
 hw/virtio/vhost-shadow-virtqueue.h | 6 ++++++
 hw/virtio/vhost-shadow-virtqueue.c | 5 +++++
 2 files changed, 11 insertions(+)

diff --git a/hw/virtio/vhost-shadow-virtqueue.h b/hw/virtio/vhost-shadow-virtqueue.h
index d04c34a589..a01a7d4a18 100644
--- a/hw/virtio/vhost-shadow-virtqueue.h
+++ b/hw/virtio/vhost-shadow-virtqueue.h
@@ -23,6 +23,9 @@ typedef struct SVQDescState {
      * guest's
      */
     unsigned int ndescs;
+
+    /* List to save or free inflight descriptors */
+    QTAILQ_ENTRY(SVQDescState) entry;
 } SVQDescState;
 
 typedef struct VhostShadowVirtqueue VhostShadowVirtqueue;
@@ -81,6 +84,9 @@ typedef struct VhostShadowVirtqueue {
     /* SVQ vring descriptors state */
     SVQDescState *desc_state;
 
+    /* Linked list to follow avail descriptors */
+    QTAILQ_HEAD(, SVQDescState) desc_state_avail;
+
     /* Next VirtQueue element that guest made available */
     VirtQueueElement *next_guest_avail_elem;
 
diff --git a/hw/virtio/vhost-shadow-virtqueue.c b/hw/virtio/vhost-shadow-virtqueue.c
index 5bd14cad96..0da72cb0ec 100644
--- a/hw/virtio/vhost-shadow-virtqueue.c
+++ b/hw/virtio/vhost-shadow-virtqueue.c
@@ -265,6 +265,8 @@ int vhost_svq_add(VhostShadowVirtqueue *svq, const struct iovec *out_sg,
 
     svq->desc_state[qemu_head].elem = elem;
     svq->desc_state[qemu_head].ndescs = ndescs;
+    QTAILQ_INSERT_TAIL(&svq->desc_state_avail, &svq->desc_state[qemu_head],
+                       entry);
     vhost_svq_kick(svq);
     return 0;
 }
@@ -451,6 +453,8 @@ static VirtQueueElement *vhost_svq_get_buf(VhostShadowVirtqueue *svq,
     svq->free_head = used_elem.id;
 
     *len = used_elem.len;
+    QTAILQ_REMOVE(&svq->desc_state_avail, &svq->desc_state[used_elem.id],
+                  entry);
     return g_steal_pointer(&svq->desc_state[used_elem.id].elem);
 }
 
@@ -665,6 +669,7 @@ void vhost_svq_start(VhostShadowVirtqueue *svq, VirtIODevice *vdev,
     svq->vring.used = qemu_memalign(qemu_real_host_page_size(), device_size);
     memset(svq->vring.used, 0, device_size);
     svq->desc_state = g_new0(SVQDescState, svq->vring.num);
+    QTAILQ_INIT(&svq->desc_state_avail);
     svq->desc_next = g_new0(uint16_t, svq->vring.num);
     for (unsigned i = 0; i < svq->vring.num - 1; i++) {
         svq->desc_next[i] = cpu_to_le16(i + 1);
-- 
2.31.1