[RFC PATCH for 8.0 06/13] virtio: refactor qemu_get_virtqueue_element

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

The core of the function is useful to transform from VirtQueueElementOld
to VirtQueueElement. Extract from qemu_get_virtqueue_element, and leave
there the handling of QEMUFile.

No functional change intended.

Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
---
 hw/virtio/virtio.c | 68 ++++++++++++++++++++++++++++------------------
 1 file changed, 42 insertions(+), 26 deletions(-)

diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index 6efff3d441..b0245ce4e8 100644
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -2297,50 +2297,66 @@ typedef struct VirtQueueElementOld {
     struct iovec out_sg[VIRTQUEUE_MAX_SIZE];
 } VirtQueueElementOld;
 
-void *qemu_get_virtqueue_element(VirtIODevice *vdev, QEMUFile *f, size_t sz)
+/* Convert VirtQueueElementOld to VirtQueueElement */
+static void *qemu_get_virtqueue_element_from_old(VirtIODevice *vdev,
+                                               const VirtQueueElementOld *data,
+                                               size_t sz)
 {
-    VirtQueueElement *elem;
-    VirtQueueElementOld data;
-    int i;
-
-    qemu_get_buffer(f, (uint8_t *)&data, sizeof(VirtQueueElementOld));
-
-    /* TODO: teach all callers that this can fail, and return failure instead
-     * of asserting here.
-     * This is just one thing (there are probably more) that must be
-     * fixed before we can allow NDEBUG compilation.
-     */
-    assert(ARRAY_SIZE(data.in_addr) >= data.in_num);
-    assert(ARRAY_SIZE(data.out_addr) >= data.out_num);
-
-    elem = virtqueue_alloc_element(sz, data.out_num, data.in_num);
-    elem->index = data.index;
+    VirtQueueElement *elem = virtqueue_alloc_element(sz, data->out_num,
+                                                     data->in_num);
+    elem->index = data->index;
 
-    for (i = 0; i < elem->in_num; i++) {
-        elem->in_addr[i] = data.in_addr[i];
+    for (uint16_t i = 0; i < elem->in_num; i++) {
+        elem->in_addr[i] = data->in_addr[i];
     }
 
-    for (i = 0; i < elem->out_num; i++) {
-        elem->out_addr[i] = data.out_addr[i];
+    for (uint16_t i = 0; i < elem->out_num; i++) {
+        elem->out_addr[i] = data->out_addr[i];
     }
 
-    for (i = 0; i < elem->in_num; i++) {
+    for (uint16_t i = 0; i < elem->in_num; i++) {
         /* Base is overwritten by virtqueue_map.  */
         elem->in_sg[i].iov_base = 0;
-        elem->in_sg[i].iov_len = data.in_sg[i].iov_len;
+        elem->in_sg[i].iov_len = data->in_sg[i].iov_len;
     }
 
-    for (i = 0; i < elem->out_num; i++) {
+    for (uint16_t i = 0; i < elem->out_num; i++) {
         /* Base is overwritten by virtqueue_map.  */
         elem->out_sg[i].iov_base = 0;
-        elem->out_sg[i].iov_len = data.out_sg[i].iov_len;
+        elem->out_sg[i].iov_len = data->out_sg[i].iov_len;
     }
 
+    virtqueue_map(vdev, elem);
+    return elem;
+}
+
+static bool vq_element_in_range(void *opaque, int version_id)
+{
+    VirtQueueElementOld *data = opaque;
+
+    return ARRAY_SIZE(data->in_addr) >= data->in_num &&
+           ARRAY_SIZE(data->out_addr) >= data->out_num;
+}
+
+void *qemu_get_virtqueue_element(VirtIODevice *vdev, QEMUFile *f, size_t sz)
+{
+    VirtQueueElement *elem;
+    VirtQueueElementOld data;
+
+    qemu_get_buffer(f, (uint8_t *)&data, sizeof(VirtQueueElementOld));
+
+    /* TODO: teach all callers that this can fail, and return failure instead
+     * of asserting here.
+     * This is just one thing (there are probably more) that must be
+     * fixed before we can allow NDEBUG compilation.
+     */
+    assert(vq_element_in_range(&data, 0));
+
+    elem = qemu_get_virtqueue_element_from_old(vdev, &data, sz);
     if (virtio_host_has_feature(vdev, VIRTIO_F_RING_PACKED)) {
         qemu_get_be32s(f, &elem->ndescs);
     }
 
-    virtqueue_map(vdev, elem);
     return elem;
 }
 
-- 
2.31.1