[PATCH] virtio-mmio : fix the crash in the vm shutdown

[Cindy Lu <lulu@redhat.com>]

The root cause for this crash is the ioeventfd not stopped while the VM stop.
The callback for vmstate_change was not implement in virtio-mmio bus

Reproduce step
load the vm with
 -M microvm \
  -netdev tap,id=net0,vhostforce,script=no,downscript=no  \
  -device virtio-net-device,netdev=net0\

After the VM boot, login the vm and then shutdown the vm

System will crash
[Current thread is 1 (Thread 0x7ffff6edde00 (LWP 374378))]
(gdb) bt
0  0x00005555558f18b4 in qemu_flush_or_purge_queued_packets (purge=false, nc=0x55500252e850) at ../net/net.c:636
1  qemu_flush_queued_packets (nc=0x55500252e850) at ../net/net.c:656
2  0x0000555555b6c363 in virtio_queue_notify_vq (vq=0x7fffe7e2b010) at ../hw/virtio/virtio.c:2339
3  virtio_queue_host_notifier_read (n=0x7fffe7e2b08c) at ../hw/virtio/virtio.c:3583
4  0x0000555555de7b5a in aio_dispatch_handler (ctx=ctx@entry=0x5555567c5780, node=0x555556b83fd0) at ../util/aio-posix.c:329
5  0x0000555555de8454 in aio_dispatch_ready_handlers (ready_list=<optimized out>, ctx=<optimized out>) at ../util/aio-posix.c:359
6  aio_poll (ctx=0x5555567c5780, blocking=blocking@entry=false) at ../util/aio-posix.c:662
7  0x0000555555cce0cc in monitor_cleanup () at ../monitor/monitor.c:645
8  0x0000555555b06bd2 in qemu_cleanup () at ../softmmu/runstate.c:822
9  0x000055555586e693 in main (argc=<optimized out>, argv=<optimized out>, envp=<optimized out>) at ../softmmu/main.c:51

Signed-off-by: Cindy Lu <lulu@redhat.com>
---
 hw/virtio/virtio-mmio.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/hw/virtio/virtio-mmio.c b/hw/virtio/virtio-mmio.c
index 7b3ebca178..72da12fea5 100644
--- a/hw/virtio/virtio-mmio.c
+++ b/hw/virtio/virtio-mmio.c
@@ -817,6 +817,17 @@ static char *virtio_mmio_bus_get_dev_path(DeviceState *dev)
     return path;
 }
 
+static void virtio_mmio_vmstate_change(DeviceState *d, bool running)
+{
+    VirtIOMMIOProxy *proxy = VIRTIO_MMIO(d);
+
+    if (running) {
+        virtio_mmio_start_ioeventfd(proxy);
+    } else {
+        virtio_mmio_stop_ioeventfd(proxy);
+    }
+}
+
 static void virtio_mmio_bus_class_init(ObjectClass *klass, void *data)
 {
     BusClass *bus_class = BUS_CLASS(klass);
@@ -832,6 +843,7 @@ static void virtio_mmio_bus_class_init(ObjectClass *klass, void *data)
     k->ioeventfd_enabled = virtio_mmio_ioeventfd_enabled;
     k->ioeventfd_assign = virtio_mmio_ioeventfd_assign;
     k->pre_plugged = virtio_mmio_pre_plugged;
+    k->vmstate_change = virtio_mmio_vmstate_change;
     k->has_variable_vring_alignment = true;
     bus_class->max_dev = 1;
     bus_class->get_dev_path = virtio_mmio_bus_get_dev_path;
-- 
2.21.3