[Qemu-devel] [PATCH V2 1/1] virtio:Allocate temporary VirtQueueElementOld on heap

[Jaya Tiwari <tiwari.jaya18@gmail.com>]

As per the list of functions in :
http://wiki.qemu.org/BiteSizedTasks#Large_frames,
qemu_get_virtqueue_element  and qemu_put_virtqueue_element
have large arrays on stack. Hence, moving them to heap
This reduced their stack size from something 49248
to fit into less than 200.

Signed-off-by: Jaya Tiwari <tiwari.jaya18@gmail.com>
---
 hw/virtio/virtio.c | 37 +++++++++++++++++++------------------
 1 file changed, 19 insertions(+), 18 deletions(-)

diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index 08275a9..027e7e2 100644
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -636,67 +636,68 @@ typedef struct VirtQueueElementOld {
 void *qemu_get_virtqueue_element(QEMUFile *f, size_t sz)
 {
     VirtQueueElement *elem;
-    VirtQueueElementOld data;
+    VirtQueueElementOld *data = g_new(VirtQueueElementOld, 1);
     int i;
 
-    qemu_get_buffer(f, (uint8_t *)&data, sizeof(VirtQueueElementOld));
+    qemu_get_buffer(f, (uint8_t *)data, sizeof(VirtQueueElementOld));
 
-    elem = virtqueue_alloc_element(sz, data.out_num, data.in_num);
-    elem->index = data.index;
+    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];
+        elem->in_addr[i] = data->in_addr[i];
     }
 
     for (i = 0; i < elem->out_num; i++) {
-        elem->out_addr[i] = data.out_addr[i];
+        elem->out_addr[i] = data->out_addr[i];
     }
 
     for (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++) {
         /* 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;
     }
 
+    g_free(data);
     virtqueue_map(elem);
     return elem;
 }
 
 void qemu_put_virtqueue_element(QEMUFile *f, VirtQueueElement *elem)
 {
-    VirtQueueElementOld data;
+    VirtQueueElementOld *data = g_new0(VirtQueueElementOld, 1);
     int i;
 
-    memset(&data, 0, sizeof(data));
-    data.index = elem->index;
-    data.in_num = elem->in_num;
-    data.out_num = elem->out_num;
+    data->index = elem->index;
+    data->in_num = elem->in_num;
+    data->out_num = elem->out_num;
 
     for (i = 0; i < elem->in_num; i++) {
-        data.in_addr[i] = elem->in_addr[i];
+        data->in_addr[i] = elem->in_addr[i];
     }
 
     for (i = 0; i < elem->out_num; i++) {
-        data.out_addr[i] = elem->out_addr[i];
+        data->out_addr[i] = elem->out_addr[i];
     }
 
     for (i = 0; i < elem->in_num; i++) {
         /* Base is overwritten by virtqueue_map when loading.  Do not
          * save it, as it would leak the QEMU address space layout.  */
-        data.in_sg[i].iov_len = elem->in_sg[i].iov_len;
+        data->in_sg[i].iov_len = elem->in_sg[i].iov_len;
     }
 
     for (i = 0; i < elem->out_num; i++) {
         /* Do not save iov_base as above.  */
-        data.out_sg[i].iov_len = elem->out_sg[i].iov_len;
+        data->out_sg[i].iov_len = elem->out_sg[i].iov_len;
     }
-    qemu_put_buffer(f, (uint8_t *)&data, sizeof(VirtQueueElementOld));
+    qemu_put_buffer(f, (uint8_t *)data, sizeof(VirtQueueElementOld));
+    g_free(data);
 }
 
 /* virtio device */
-- 
1.8.1.2