Re: [Qemu-devel] [PATCH] net: Forbid dealing with packets when VM is not running

[Stefan Hajnoczi]

On Mon, Aug 18, 2014 at 04:32:42PM +0800, zhanghailiang wrote:
> On 2014/8/18 14:55, Jason Wang wrote:
> >On 08/18/2014 12:46 PM, zhanghailiang wrote:
> >>diff --git a/net/net.c b/net/net.c
> >>index 6d930ea..21f0d48 100644
> >>--- a/net/net.c
> >>+++ b/net/net.c
> >>@@ -242,6 +242,29 @@ NetClientState *qemu_new_net_client(NetClientInfo 
> >>*info,
> >>      return nc;
> >>  }
> >>
> >>+static void nic_vmstate_change_handler(void *opaque,
> >>+                                       int running,
> >>+                                       RunState state)
> >>+{
> >>+    NICState *nic = opaque;
> >>+    NetClientState *nc;
> >>+    int i, queues;
> >>+
> >>+    if (!running) {
> >>+        return;
> >>+    }
> >>+
> >>+    queues = MAX(1, nic->conf->peers.queues);
> >>+    for (i = 0; i<  queues; i++) {
> >>+        nc =&nic->ncs[i];
> >>+        if (nc->receive_disabled
> >>+            || (nc->info->can_receive&&  !nc->info->can_receive(nc))) {
> >>+            continue;
> >>+        }
> >>+        qemu_flush_queued_packets(nc);
> >
> >How about simply purge the receive queue during stop? If ok, there's no
> >need to introduce extra vmstate change handler.
> >
> 
> I don't know whether it is OK to purge the receive packages, it was
> suggested by Stefan Hajnoczi, and i am waiting for his opinion .:)
> 
> I think we still need the extra vmstate change handler, Without the
> change handler, we don't know if the VM will go to stop and the time
> when to call qemu_purge_queued_packets.

qemu_flush_queued_packets() sets nc->received_disabled = 0.  This may be
needed to get packets flowing again if ->receive() previously returned 0.

Purging the queue does not clear nc->received_disabled so it is not
enough.

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