[PATCH v3 2/2] vhost-net: Fix the virtio features negotiation flaw

[huangy81]

From: Hyman Huang(黄勇) <huang...@chinatelecom.cn>

Save the acked_features once it be configured by guest
virtio driver so it can't miss any features.

Note that this patch also change the features saving logic
in chr_closed_bh, which originally backup features no matter
whether the features are 0 or not, but now do it only if
features aren't 0.

As to reset acked_features to 0 if needed, Qemu always
keeping the backup acked_features up-to-date, and save the
acked_features after virtio_net_set_features in advance,
including reset acked_features to 0, so the behavior is
also covered.

Signed-off-by: Hyman Huang(黄勇) <huang...@chinatelecom.cn>
Signed-off-by: Guoyi Tu <t...@chinatelecom.cn>
---
 hw/net/vhost_net.c      | 9 +++++++++
 hw/net/virtio-net.c     | 5 +++++
 include/net/vhost_net.h | 2 ++
 net/vhost-user.c        | 6 +-----
 4 files changed, 17 insertions(+), 5 deletions(-)

diff --git a/hw/net/vhost_net.c b/hw/net/vhost_net.c
index d28f8b9..2bffc27 100644
--- a/hw/net/vhost_net.c
+++ b/hw/net/vhost_net.c
@@ -141,6 +141,15 @@ uint64_t vhost_net_get_acked_features(VHostNetState *net)
     return net->dev.acked_features;
 }
 
+void vhost_net_save_acked_features(NetClientState *nc)
+{
+    if (nc->info->type != NET_CLIENT_DRIVER_VHOST_USER) {
+        return;
+    }
+
+    vhost_user_save_acked_features(nc, false);
+}
+
 static int vhost_net_get_fd(NetClientState *backend)
 {
     switch (backend->info->type) {
diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
index e9f696b..5f8f788 100644
--- a/hw/net/virtio-net.c
+++ b/hw/net/virtio-net.c
@@ -924,6 +924,11 @@ static void virtio_net_set_features(VirtIODevice *vdev, 
uint64_t features)
             continue;
         }
         vhost_net_ack_features(get_vhost_net(nc->peer), features);
+        /*
+         * keep acked_features in NetVhostUserState up-to-date so it
+         * can't miss any features configured by guest virtio driver.
+         */
+        vhost_net_save_acked_features(nc->peer);
     }
 
     if (virtio_has_feature(features, VIRTIO_NET_F_CTRL_VLAN)) {
diff --git a/include/net/vhost_net.h b/include/net/vhost_net.h
index 387e913..3a5579b 100644
--- a/include/net/vhost_net.h
+++ b/include/net/vhost_net.h
@@ -46,6 +46,8 @@ int vhost_set_vring_enable(NetClientState * nc, int enable);
 
 uint64_t vhost_net_get_acked_features(VHostNetState *net);
 
+void vhost_net_save_acked_features(NetClientState *nc);
+
 int vhost_net_set_mtu(struct vhost_net *net, uint16_t mtu);
 
 #endif
diff --git a/net/vhost-user.c b/net/vhost-user.c
index 74f349c..c512cc9 100644
--- a/net/vhost-user.c
+++ b/net/vhost-user.c
@@ -258,11 +258,7 @@ static void chr_closed_bh(void *opaque)
     s = DO_UPCAST(NetVhostUserState, nc, ncs[0]);
 
     for (i = queues -1; i >= 0; i--) {
-        s = DO_UPCAST(NetVhostUserState, nc, ncs[i]);
-
-        if (s->vhost_net) {
-            s->acked_features = vhost_net_get_acked_features(s->vhost_net);
-        }
+        vhost_user_save_acked_features(ncs[i], false);
     }
 
     qmp_set_link(name, false, &err);
-- 
1.8.3.1