[Qemu-devel] [PATCH] virtio-net: unify vhost-net start/stop

["Michael S. Tsirkin" <mst@redhat.com>]

Move all of vhost-net start/stop logic to a single routine,
and call it from everywhere.

Additionally, start/stop vhost-net on link up/down:
we should not transmit anything if user asked us to
put the link down.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
 hw/virtio-net.c |   37 +++++++++++++++++--------------------
 1 files changed, 17 insertions(+), 20 deletions(-)

diff --git a/hw/virtio-net.c b/hw/virtio-net.c
index 075f72d..d3fc400 100644
--- a/hw/virtio-net.c
+++ b/hw/virtio-net.c
@@ -51,6 +51,7 @@ typedef struct VirtIONet
     uint8_t nouni;
     uint8_t nobcast;
     uint8_t vhost_started;
+    bool vm_running;
     VMChangeStateEntry *vmstate;
     struct {
         int in_use;
@@ -107,6 +108,8 @@ static void virtio_net_set_link_status(VLANClientState *nc)
 
     if (n->status != old_status)
         virtio_notify_config(&n->vdev);
+
+    virtio_net_set_status(n->vdev.status);
 }
 
 static void virtio_net_reset(VirtIODevice *vdev)
@@ -120,10 +123,6 @@ static void virtio_net_reset(VirtIODevice *vdev)
     n->nomulti = 0;
     n->nouni = 0;
     n->nobcast = 0;
-    if (n->vhost_started) {
-        vhost_net_stop(tap_get_vhost_net(n->nic->nc.peer), vdev);
-        n->vhost_started = 0;
-    }
 
     /* Flush any MAC and VLAN filter table state */
     n->mac_table.in_use = 0;
@@ -726,12 +725,9 @@ static void virtio_net_save(QEMUFile *f, void *opaque)
 {
     VirtIONet *n = opaque;
 
-    if (n->vhost_started) {
-        /* TODO: should we really stop the backend?
-         * If we don't, it might keep writing to memory. */
-        vhost_net_stop(tap_get_vhost_net(n->nic->nc.peer), &n->vdev);
-        n->vhost_started = 0;
-    }
+    /* At this point, backend must be stopped, otherwise
+     * it might keep writing to memory. */
+    assert(!n->vhost_started);
     virtio_save(&n->vdev, f);
 
     qemu_put_buffer(f, n->mac, ETH_ALEN);
@@ -876,11 +872,13 @@ static void virtio_net_set_status(struct VirtIODevice *vdev, uint8_t status)
     if (!tap_get_vhost_net(n->nic->nc.peer)) {
         return;
     }
-    if (!!n->vhost_started == !!(status & VIRTIO_CONFIG_S_DRIVER_OK)) {
+    if (!!n->vhost_started == (status & VIRTIO_CONFIG_S_DRIVER_OK) &&
+                                (n->status & VIRTIO_NET_S_LINK_UP) &&
+                                n->vm_running) {
         return;
     }
-    if (status & VIRTIO_CONFIG_S_DRIVER_OK) {
-        int r = vhost_net_start(tap_get_vhost_net(n->nic->nc.peer), vdev);
+    if (!n->vhost_started) {
+        int r = vhost_net_start(tap_get_vhost_net(n->nic->nc.peer), &n->vdev);
         if (r < 0) {
             fprintf(stderr, "unable to start vhost net: %d: "
                     "falling back on userspace virtio\n", -r);
@@ -888,7 +886,7 @@ static void virtio_net_set_status(struct VirtIODevice *vdev, uint8_t status)
             n->vhost_started = 1;
         }
     } else {
-        vhost_net_stop(tap_get_vhost_net(n->nic->nc.peer), vdev);
+        vhost_net_stop(tap_get_vhost_net(n->nic->nc.peer), &n->vdev);
         n->vhost_started = 0;
     }
 }
@@ -896,11 +894,11 @@ static void virtio_net_set_status(struct VirtIODevice *vdev, uint8_t status)
 static void virtio_net_vmstate_change(void *opaque, int running, int reason)
 {
     VirtIONet *n = opaque;
-    uint8_t status = running ? VIRTIO_CONFIG_S_DRIVER_OK : 0;
+    n->vm_running = running;
     /* This is called when vm is started/stopped,
-     * it will start/stop vhost backend if * appropriate
+     * it will start/stop vhost backend if appropriate
      * e.g. after migration. */
-    virtio_net_set_status(&n->vdev, n->vdev.status & status);
+    virtio_net_set_status(&n->vdev, n->vdev.status);
 }
 
 VirtIODevice *virtio_net_init(DeviceState *dev, NICConf *conf)
@@ -951,9 +949,8 @@ void virtio_net_exit(VirtIODevice *vdev)
     VirtIONet *n = DO_UPCAST(VirtIONet, vdev, vdev);
     qemu_del_vm_change_state_handler(n->vmstate);
 
-    if (n->vhost_started) {
-        vhost_net_stop(tap_get_vhost_net(n->nic->nc.peer), vdev);
-    }
+    /* This will stop vhost backend if appropriate. */
+    virtio_net_set_status(vdev, 0);
 
     qemu_purge_queued_packets(&n->nic->nc);
 
-- 
1.7.3-rc1