iov: Introduce a new file for helpers around iovs, add iov_from_buf()

The virtio-net code uses iov_fill() which fills an iov from a linear
buffer. The virtio-serial-bus code does something similar in an
open-coded function.

Create a new iov.c file that has iov_from_buf().

Convert virtio-net and virtio-serial-bus over to use this functionality.
virtio-net used ints to hold sizes, the new function is going to use
size_t types.

Later commits will add the opposite functionality -- going from an iov
to a linear buffer.

Signed-off-by: Amit Shah <amit.shah@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

1 files changed, 7 insertions, 8 deletions

diff --git a/hw/virtio-serial-bus.c b/hw/virtio-serial-bus.c
index 6befd4d139..a72b6b53d3 100644
--- a/hw/virtio-serial-bus.c
+++ b/hw/virtio-serial-bus.c
@@ -15,6 +15,7 @@
  * the COPYING file in the top-level directory.
  */
 
+#include "iov.h"
 #include "monitor.h"
 #include "qemu-queue.h"
 #include "sysbus.h"
@@ -84,27 +85,25 @@ static size_t write_to_port(VirtIOSerialPort *port,
 {
     VirtQueueElement elem;
     VirtQueue *vq;
-    size_t offset = 0;
-    size_t len = 0;
+    size_t offset;
 
     vq = port->ivq;
     if (!virtio_queue_ready(vq)) {
         return 0;
     }
 
+    offset = 0;
     while (offset < size) {
-        int i;
+        size_t len;
 
         if (!virtqueue_pop(vq, &elem)) {
             break;
         }
 
-        for (i = 0; offset < size && i < elem.in_num; i++) {
-            len = MIN(elem.in_sg[i].iov_len, size - offset);
+        len = iov_from_buf(elem.in_sg, elem.in_num,
+                           buf + offset, size - offset);
+        offset += len;
 
-            memcpy(elem.in_sg[i].iov_base, buf + offset, len);
-            offset += len;
-        }
         virtqueue_push(vq, &elem, len);
     }