[RFC 2/8] virtio: Create/destroy/reset VirtQueue In-Order hash table

[Jonah Palmer <jonah.palmer@oracle.com>]

Define a GLib hash table (GHashTable) member in a device's VirtQueue
and add its creation, destruction, and reset functions appropriately.
Also define a function to handle the deallocation of InOrderVQElement
values whenever they're removed from the hash table or the hash table
is destroyed. This hash table is to be used when the device is using
the VIRTIO_F_IN_ORDER transport feature.

A VirtQueue's in-order hash table will take in a uint16_t key with a
InOrderVQElement value as its key-value pair.

The hash table will be used as a buffer mechanism for completed,
out-of-order VirtQueueElements until they can be used in the same order
in which they were made available to the device.

Signed-off-by: Jonah Palmer <jonah.palmer@oracle.com>
---
 hw/virtio/virtio.c | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)

diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index fb6b4ccd83..d2afeeb59a 100644
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -152,6 +152,9 @@ struct VirtQueue
     EventNotifier host_notifier;
     bool host_notifier_enabled;
     QLIST_ENTRY(VirtQueue) node;
+
+    /* In-Order */
+    GHashTable *in_order_ht;
 };
 
 const char *virtio_device_names[] = {
@@ -2070,6 +2073,16 @@ static enum virtio_device_endian virtio_current_cpu_endian(void)
     }
 }
 
+/* 
+ * Called when an element is removed from the hash table
+ * or when the hash table is destroyed.
+ */
+static void free_in_order_vq_element(gpointer data)
+{
+    InOrderVQElement *elem = (InOrderVQElement *)data;
+    g_free(elem);
+}
+
 static void __virtio_queue_reset(VirtIODevice *vdev, uint32_t i)
 {
     vdev->vq[i].vring.desc = 0;
@@ -2087,6 +2100,9 @@ static void __virtio_queue_reset(VirtIODevice *vdev, uint32_t i)
     vdev->vq[i].notification = true;
     vdev->vq[i].vring.num = vdev->vq[i].vring.num_default;
     vdev->vq[i].inuse = 0;
+    if (vdev->vq[i].in_order_ht != NULL) {
+        g_hash_table_remove_all(vdev->vq[i].in_order_ht);
+    }
     virtio_virtqueue_reset_region_cache(&vdev->vq[i]);
 }
 
@@ -2334,6 +2350,13 @@ VirtQueue *virtio_add_queue(VirtIODevice *vdev, int queue_size,
     vdev->vq[i].vring.align = VIRTIO_PCI_VRING_ALIGN;
     vdev->vq[i].handle_output = handle_output;
     vdev->vq[i].used_elems = g_new0(VirtQueueElement, queue_size);
+    vdev->vq[i].in_order_ht = NULL;
+
+    if (virtio_host_has_feature(vdev, VIRTIO_F_IN_ORDER)) {
+        vdev->vq[i].in_order_ht =
+            g_hash_table_new_full(g_direct_hash, g_direct_equal, NULL,
+                                  free_in_order_vq_element);
+    }
 
     return &vdev->vq[i];
 }
@@ -2345,6 +2368,10 @@ void virtio_delete_queue(VirtQueue *vq)
     vq->handle_output = NULL;
     g_free(vq->used_elems);
     vq->used_elems = NULL;
+    if (virtio_host_has_feature(vq->vdev, VIRTIO_F_IN_ORDER)) {
+        g_hash_table_destroy(vq->in_order_ht);
+        vq->in_order_ht = NULL;
+    }
     virtio_virtqueue_reset_region_cache(vq);
 }
 
-- 
2.39.3