[Qemu-devel] [PATCH] hw/net/virtio-net: Allocating Large sized arrays to heap

[Zhou Jie <zhoujie2011@cn.fujitsu.com>]

virtio_net_flush_tx has a huge stack usage of 16392 bytes approx.
Moving large arrays to heap to reduce stack usage.

Signed-off-by: Zhou Jie <zhoujie2011@cn.fujitsu.com>
---
 hw/net/virtio-net.c | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
index 5798f87..cab7bbc 100644
--- a/hw/net/virtio-net.c
+++ b/hw/net/virtio-net.c
@@ -1213,6 +1213,7 @@ static int32_t virtio_net_flush_tx(VirtIONetQueue *q)
     VirtIONet *n = q->n;
     VirtIODevice *vdev = VIRTIO_DEVICE(n);
     VirtQueueElement *elem;
+    struct iovec *sg = NULL, *sg2 = NULL;
     int32_t num_packets = 0;
     int queue_index = vq2q(virtio_get_queue_index(q->tx_vq));
     if (!(vdev->status & VIRTIO_CONFIG_S_DRIVER_OK)) {
@@ -1224,10 +1225,12 @@ static int32_t virtio_net_flush_tx(VirtIONetQueue *q)
         return num_packets;
     }
 
+    sg = g_new(struct iovec, VIRTQUEUE_MAX_SIZE);
+    sg2 = g_new(struct iovec, VIRTQUEUE_MAX_SIZE + 1);
     for (;;) {
         ssize_t ret;
         unsigned int out_num;
-        struct iovec sg[VIRTQUEUE_MAX_SIZE], sg2[VIRTQUEUE_MAX_SIZE + 1], *out_sg;
+        struct iovec *out_sg;
         struct virtio_net_hdr_mrg_rxbuf mhdr;
 
         elem = virtqueue_pop(q->tx_vq, sizeof(VirtQueueElement));
@@ -1252,7 +1255,7 @@ static int32_t virtio_net_flush_tx(VirtIONetQueue *q)
                 virtio_net_hdr_swap(vdev, (void *) &mhdr);
                 sg2[0].iov_base = &mhdr;
                 sg2[0].iov_len = n->guest_hdr_len;
-                out_num = iov_copy(&sg2[1], ARRAY_SIZE(sg2) - 1,
+                out_num = iov_copy(&sg2[1], VIRTQUEUE_MAX_SIZE,
                                    out_sg, out_num,
                                    n->guest_hdr_len, -1);
                 if (out_num == VIRTQUEUE_MAX_SIZE) {
@@ -1269,10 +1272,10 @@ static int32_t virtio_net_flush_tx(VirtIONetQueue *q)
          */
         assert(n->host_hdr_len <= n->guest_hdr_len);
         if (n->host_hdr_len != n->guest_hdr_len) {
-            unsigned sg_num = iov_copy(sg, ARRAY_SIZE(sg),
+            unsigned sg_num = iov_copy(sg, VIRTQUEUE_MAX_SIZE,
                                        out_sg, out_num,
                                        0, n->host_hdr_len);
-            sg_num += iov_copy(sg + sg_num, ARRAY_SIZE(sg) - sg_num,
+            sg_num += iov_copy(sg + sg_num, VIRTQUEUE_MAX_SIZE - sg_num,
                              out_sg, out_num,
                              n->guest_hdr_len, -1);
             out_num = sg_num;
@@ -1284,6 +1287,8 @@ static int32_t virtio_net_flush_tx(VirtIONetQueue *q)
         if (ret == 0) {
             virtio_queue_set_notification(q->tx_vq, 0);
             q->async_tx.elem = elem;
+            g_free(sg);
+            g_free(sg2);
             return -EBUSY;
         }
 
@@ -1296,6 +1301,8 @@ drop:
             break;
         }
     }
+    g_free(sg);
+    g_free(sg2);
     return num_packets;
 }
 
-- 
2.5.5