virtio: introduce qemu_get/put_virtqueue_element

Move allocation to virtio functions also when loading/saving a
VirtQueueElement.  This will also let the load/save functions
keep backwards compatibility when the VirtQueueElement layout
is changed.

Reviewed-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

hw/block/virtio-blk.c

@@ -808,8 +808,7 @@ static void virtio_blk_save_device(VirtIODevice *vdev, QEMUFile *f)
 
     while (req) {
         qemu_put_sbyte(f, 1);
-        qemu_put_buffer(f, (unsigned char *)&req->elem,
-                        sizeof(VirtQueueElement));
+        qemu_put_virtqueue_element(f, &req->elem);
         req = req->next;
     }
     qemu_put_sbyte(f, 0);
@@ -832,14 +831,11 @@ static int virtio_blk_load_device(VirtIODevice *vdev, QEMUFile *f,
     VirtIOBlock *s = VIRTIO_BLK(vdev);
 
     while (qemu_get_sbyte(f)) {
-        VirtIOBlockReq *req = g_new(VirtIOBlockReq, 1);
+        VirtIOBlockReq *req;
+        req = qemu_get_virtqueue_element(f, sizeof(VirtIOBlockReq));
         virtio_blk_init_request(s, req);
-        qemu_get_buffer(f, (unsigned char *)&req->elem,
-                        sizeof(VirtQueueElement));
         req->next = s->rq;
         s->rq = req;
-
-        virtqueue_map(&req->elem);
     }
 
     return 0;

hw/char/virtio-serial-bus.c

@@ -646,9 +646,7 @@ static void virtio_serial_save_device(VirtIODevice *vdev, QEMUFile *f)
         if (elem_popped) {
             qemu_put_be32s(f, &port->iov_idx);
             qemu_put_be64s(f, &port->iov_offset);
-
-            qemu_put_buffer(f, (unsigned char *)port->elem,
-                            sizeof(VirtQueueElement));
+            qemu_put_virtqueue_element(f, port->elem);
         }
     }
 }
@@ -723,10 +721,8 @@ static int fetch_active_ports_list(QEMUFile *f, int version_id,
                 qemu_get_be32s(f, &port->iov_idx);
                 qemu_get_be64s(f, &port->iov_offset);
 
-                port->elem = g_new(VirtQueueElement, 1);
-                qemu_get_buffer(f, (unsigned char *)port->elem,
-                                sizeof(VirtQueueElement));
-                virtqueue_map(port->elem);
+                port->elem =
+                    qemu_get_virtqueue_element(f, sizeof(VirtQueueElement));
 
                 /*
                  *  Port was throttled on source machine.  Let's

hw/scsi/virtio-scsi.c

@@ -189,7 +189,7 @@ static void virtio_scsi_save_request(QEMUFile *f, SCSIRequest *sreq)
 
     assert(n < vs->conf.num_queues);
     qemu_put_be32s(f, &n);
-    qemu_put_buffer(f, (unsigned char *)&req->elem, sizeof(req->elem));
+    qemu_put_virtqueue_element(f, &req->elem);
 }
 
 static void *virtio_scsi_load_request(QEMUFile *f, SCSIRequest *sreq)
@@ -202,12 +202,9 @@ static void *virtio_scsi_load_request(QEMUFile *f, SCSIRequest *sreq)
 
     qemu_get_be32s(f, &n);
     assert(n < vs->conf.num_queues);
-    req = g_malloc(sizeof(VirtIOSCSIReq) + vs->cdb_size);
-    qemu_get_buffer(f, (unsigned char *)&req->elem, sizeof(req->elem));
+    req = qemu_get_virtqueue_element(f, sizeof(VirtIOSCSIReq) + vs->cdb_size);
     virtio_scsi_init_req(s, vs->cmd_vqs[n], req);
 
-    virtqueue_map(&req->elem);
-
     if (virtio_scsi_parse_req(req, sizeof(VirtIOSCSICmdReq) + vs->cdb_size,
                               sizeof(VirtIOSCSICmdResp) + vs->sense_size) < 0) {
         error_report("invalid SCSI request migration data");

hw/virtio/virtio.c

@@ -576,6 +576,19 @@ void *virtqueue_pop(VirtQueue *vq, size_t sz)
     return elem;
 }
 
+void *qemu_get_virtqueue_element(QEMUFile *f, size_t sz)
+{
+    VirtQueueElement *elem = g_malloc(sz);
+    qemu_get_buffer(f, (uint8_t *)elem, sizeof(VirtQueueElement));
+    virtqueue_map(elem);
+    return elem;
+}
+
+void qemu_put_virtqueue_element(QEMUFile *f, VirtQueueElement *elem)
+{
+    qemu_put_buffer(f, (uint8_t *)elem, sizeof(VirtQueueElement));
+}
+
 /* virtio device */
 static void virtio_notify_vector(VirtIODevice *vdev, uint16_t vector)
 {

include/hw/virtio/virtio.h

@@ -153,6 +153,8 @@ void virtqueue_fill(VirtQueue *vq, const VirtQueueElement *elem,
 
 void virtqueue_map(VirtQueueElement *elem);
 void *virtqueue_pop(VirtQueue *vq, size_t sz);
+void *qemu_get_virtqueue_element(QEMUFile *f, size_t sz);
+void qemu_put_virtqueue_element(QEMUFile *f, VirtQueueElement *elem);
 int virtqueue_avail_bytes(VirtQueue *vq, unsigned int in_bytes,
                           unsigned int out_bytes);
 void virtqueue_get_avail_bytes(VirtQueue *vq, unsigned int *in_bytes,