[Qemu-devel] [PATCH 14/18] vhost-net: save & restore vhost-user acked features

[marcandre . lureau]

From: Marc-André Lureau <address@hidden>

The initial vhost-user connection sets the features to be negotiated
with the driver. Renegotiation isn't possible without device reset.

To handle reconnection of vhost-user backend, ensure the same set of
features are provided, and reuse already acked features.

Signed-off-by: Marc-André Lureau <address@hidden>
---
 hw/net/vhost_net.c       | 21 ++++++++++++++++++++-
 include/net/vhost-user.h |  1 +
 include/net/vhost_net.h  |  3 +++
 net/vhost-user.c         | 10 ++++++++++
 4 files changed, 34 insertions(+), 1 deletion(-)

diff --git a/hw/net/vhost_net.c b/hw/net/vhost_net.c
index 6c40c4e..ee39e9c 100644
--- a/hw/net/vhost_net.c
+++ b/hw/net/vhost_net.c
@@ -120,6 +120,11 @@ uint64_t vhost_net_get_max_queues(VHostNetState *net)
     return net->dev.max_queues;
 }
 
+uint64_t vhost_net_get_acked_features(VHostNetState *net)
+{
+    return net->dev.acked_features;
+}
+
 static int vhost_net_get_fd(NetClientState *backend)
 {
     switch (backend->info->type) {
@@ -148,6 +153,7 @@ struct vhost_net *vhost_net_init(VhostNetOptions *options)
     int r;
     bool backend_kernel = options->backend_type == VHOST_BACKEND_TYPE_KERNEL;
     struct vhost_net *net = g_malloc(sizeof *net);
+    uint64_t features = 0;
 
     if (!options->net_backend) {
         fprintf(stderr, "vhost-net requires net backend to be setup\n");
@@ -197,8 +203,21 @@ struct vhost_net *vhost_net_init(VhostNetOptions *options)
             goto fail;
         }
     }
+
     /* Set sane init value. Override when guest acks. */
-    vhost_net_ack_features(net, 0);
+    if (net->nc->info->type == NET_CLIENT_OPTIONS_KIND_VHOST_USER) {
+        features = vhost_user_get_acked_features(net->nc);
+        if (~net->dev.features & features) {
+            fprintf(stderr, "vhost lacks feature mask %" PRIu64
+                    " for backend\n",
+                    (uint64_t)(~net->dev.features & features));
+            vhost_dev_cleanup(&net->dev);
+            goto fail;
+        }
+    }
+
+    vhost_net_ack_features(net, features);
+
     return net;
 fail:
     g_free(net);
diff --git a/include/net/vhost-user.h b/include/net/vhost-user.h
index 85109f6..efae35d 100644
--- a/include/net/vhost-user.h
+++ b/include/net/vhost-user.h
@@ -13,5 +13,6 @@
 
 struct vhost_net;
 struct vhost_net *vhost_user_get_vhost_net(NetClientState *nc);
+uint64_t vhost_user_get_acked_features(NetClientState *nc);
 
 #endif /* VHOST_USER_H_ */
diff --git a/include/net/vhost_net.h b/include/net/vhost_net.h
index 3389b41..0bd4877 100644
--- a/include/net/vhost_net.h
+++ b/include/net/vhost_net.h
@@ -31,4 +31,7 @@ int vhost_net_notify_migration_done(VHostNetState *net, char* 
mac_addr);
 VHostNetState *get_vhost_net(NetClientState *nc);
 
 int vhost_set_vring_enable(NetClientState * nc, int enable);
+
+uint64_t vhost_net_get_acked_features(VHostNetState *net);
+
 #endif
diff --git a/net/vhost-user.c b/net/vhost-user.c
index 54849e9..ae63e20 100644
--- a/net/vhost-user.c
+++ b/net/vhost-user.c
@@ -23,6 +23,7 @@ typedef struct VhostUserState {
     CharDriverState *chr;
     VHostNetState *vhost_net;
     int watch;
+    uint64_t acked_features;
 } VhostUserState;
 
 typedef struct VhostUserChardevProps {
@@ -39,6 +40,13 @@ VHostNetState *vhost_user_get_vhost_net(NetClientState *nc)
     return s->vhost_net;
 }
 
+uint64_t vhost_user_get_acked_features(NetClientState *nc)
+{
+    VhostUserState *s = DO_UPCAST(VhostUserState, nc, nc);
+    assert(nc->info->type == NET_CLIENT_OPTIONS_KIND_VHOST_USER);
+    return s->acked_features;
+}
+
 static int vhost_user_running(VhostUserState *s)
 {
     return (s->vhost_net) ? 1 : 0;
@@ -58,6 +66,8 @@ static void vhost_user_stop(int queues, NetClientState *ncs[])
         }
 
         if (s->vhost_net) {
+            /* save acked features */
+            s->acked_features = vhost_net_get_acked_features(s->vhost_net);
             vhost_net_cleanup(s->vhost_net);
             s->vhost_net = NULL;
         }
-- 
2.5.5