[Qemu-devel] [PATCH v4 1/1] vhost user: add support of live migration

[Thibaut Collet]

Some vhost client/backend are able to support live migration.
To provide this service the following features must be added:
1. Add the VIRTIO_NET_F_GUEST_ANNOUNCE capability to vhost-net when netdev
   backend is vhost-user.
2. Provide a nop receive callback to vhost-user. This callback is for RARP
   packets automatically send by qemu_announce_self after a migration.
   These packets are useless for vhost user and just discarded.

Signed-off-by: Thibaut Collet <address@hidden>
---
 hw/net/vhost_net.c |    2 ++
 net/vhost-user.c   |   21 +++++++++++++++++++--
 2 files changed, 21 insertions(+), 2 deletions(-)

diff --git a/hw/net/vhost_net.c b/hw/net/vhost_net.c
index 9bd360b..668c422 100644
--- a/hw/net/vhost_net.c
+++ b/hw/net/vhost_net.c
@@ -85,6 +85,8 @@ static const int user_feature_bits[] = {
     VIRTIO_NET_F_CTRL_MAC_ADDR,
     VIRTIO_NET_F_CTRL_GUEST_OFFLOADS,
 
+    VIRTIO_NET_F_GUEST_ANNOUNCE,
+
     VIRTIO_NET_F_MQ,
 
     VHOST_INVALID_FEATURE_BIT
diff --git a/net/vhost-user.c b/net/vhost-user.c
index b51bc04..20778a1 100644
--- a/net/vhost-user.c
+++ b/net/vhost-user.c
@@ -65,6 +65,24 @@ static void vhost_user_stop(VhostUserState *s)
     s->vhost_net = 0;
 }
 
+static ssize_t vhost_user_receive(NetClientState *nc, const uint8_t *buf,
+                                  size_t size)
+{
+    /* A live migration is done. Display an error if the packet is not a RARP.
+     * RARP are just discarded: guest is already notified of live migration
+     * by the virtio-net NIC or by the vhost-user backend */
+    if (size != 60) {
+        static int display_trace = 1;
+
+        if (display_trace) {
+            fprintf(stderr,"Vhost user receives unexpected packets\n");
+            fflush(stderr);
+            display_trace = 0;
+        }
+    }
+    return size;
+}
+
 static void vhost_user_cleanup(NetClientState *nc)
 {
     VhostUserState *s = DO_UPCAST(VhostUserState, nc, nc);
@@ -90,6 +108,7 @@ static bool vhost_user_has_ufo(NetClientState *nc)
 static NetClientInfo net_vhost_user_info = {
         .type = NET_CLIENT_OPTIONS_KIND_VHOST_USER,
         .size = sizeof(VhostUserState),
+        .receive = vhost_user_receive,
         .cleanup = vhost_user_cleanup,
         .has_vnet_hdr = vhost_user_has_vnet_hdr,
         .has_ufo = vhost_user_has_ufo,
@@ -146,8 +165,6 @@ static int net_vhost_user_init(NetClientState *peer, const 
char *device,
 
         s = DO_UPCAST(VhostUserState, nc, nc);
 
-        /* We don't provide a receive callback */
-        s->nc.receive_disabled = 1;
         s->chr = chr;
         s->nc.queue_index = i;
 
-- 
1.7.10.4