[Qemu-devel] [PATCH RFC] virtio-net: don't dma while vm is stopped

[Michael S. Tsirkin]

DMA into memory while VM is stopped makes it
hard to debug migration (consequitive saves
result in different files).

Sending while vm is stopped has an even worse
effect as it confuses the bridges so that they do
not know where to send packets.

Fixing this completely is a large effort,
this patch does this for virtio-net since that
already tracks vm state.

Signed-off-by: Michael S. Tsirkin <m...@redhat.com>
---
 hw/virtio-net.c |    8 +++++++-
 1 files changed, 7 insertions(+), 1 deletions(-)

diff --git a/hw/virtio-net.c b/hw/virtio-net.c
index 7e1688c..90010e6 100644
--- a/hw/virtio-net.c
+++ b/hw/virtio-net.c
@@ -424,6 +424,9 @@ static void virtio_net_handle_rx(VirtIODevice *vdev, 
VirtQueue *vq)
 static int virtio_net_can_receive(VLANClientState *nc)
 {
     VirtIONet *n = DO_UPCAST(NICState, nc, nc)->opaque;
+    if (!n->vm_running) {
+        return 0;
+    }
 
     if (!virtio_queue_ready(n->rx_vq) ||
         !(n->vdev.status & VIRTIO_CONFIG_S_DRIVER_OK))
@@ -673,11 +676,14 @@ static int32_t virtio_net_flush_tx(VirtIONet *n, 
VirtQueue *vq)
 {
     VirtQueueElement elem;
     int32_t num_packets = 0;
-
     if (!(n->vdev.status & VIRTIO_CONFIG_S_DRIVER_OK)) {
         return num_packets;
     }
 
+    if (!n->vm_running) {
+        return 0;
+    }
+
     if (n->async_tx.elem.out_num) {
         virtio_queue_set_notification(n->tx_vq, 0);
         return num_packets;
-- 
1.7.3-rc1