Re: [PATCH 1/2] vhost-user: Refactor vhost acked features saving

[Stefano Garzarella]

On Fri, Oct 07, 2022 at 10:01:21AM -0400, Michael S. Tsirkin wrote:
On Mon, Sep 26, 2022 at 02:36:40PM +0800, huang...@chinatelecom.cn wrote:
From: Hyman Huang(黄勇) <huang...@chinatelecom.cn>
Abstract vhost acked features saving into
vhost_user_save_acked_features, export it as util function.

Signed-off-by: Hyman Huang(黄勇) <huang...@chinatelecom.cn>
Signed-off-by: Guoyi Tu <t...@chinatelecom.cn>
---
 include/net/vhost-user.h |  2 ++
 net/vhost-user.c         | 35 +++++++++++++++++++----------------
 2 files changed, 21 insertions(+), 16 deletions(-)

diff --git a/include/net/vhost-user.h b/include/net/vhost-user.h
index 5bcd8a6285..00d46613d3 100644
--- a/include/net/vhost-user.h
+++ b/include/net/vhost-user.h
@@ -14,5 +14,7 @@
 struct vhost_net;
 struct vhost_net *vhost_user_get_vhost_net(NetClientState *nc);
 uint64_t vhost_user_get_acked_features(NetClientState *nc);
+void vhost_user_save_acked_features(NetClientState *nc,
+                                    bool cleanup);

 #endif /* VHOST_USER_H */
diff --git a/net/vhost-user.c b/net/vhost-user.c
index b1a0247b59..c512cc9727 100644
--- a/net/vhost-user.c
+++ b/net/vhost-user.c
@@ -45,24 +45,31 @@ uint64_t vhost_user_get_acked_features(NetClientState *nc)
     return s->acked_features;
 }

-static void vhost_user_stop(int queues, NetClientState *ncs[])
+void vhost_user_save_acked_features(NetClientState *nc, bool cleanup)
 {
     NetVhostUserState *s;
+
+    s = DO_UPCAST(NetVhostUserState, nc, nc);
+    if (s->vhost_net) {
+        uint64_t features = vhost_net_get_acked_features(s->vhost_net);
+        if (features) {
+            s->acked_features = features;
+        }

Note it does not set  acked_features if features are 0.
Which might be the case for legacy ...
I will need to analyze this more to figure out what's
the correct behaviour....

Stefano? Raphael?

I just noticed that we now call vhost_user_stop() only in the error path 
of vhost_user_start(). We used it elsewhere, but over time we removed 
those calls.

Do we still need to save acked_feature in that path?

About doing it only if the features aren't 0, it isn't clear to me.
I see we did in e6bcb1b617 ("vhost-user: keep vhost_net after a 
disconnection"). @Marc-André do you remember why?

Thanks,
Stefano


+
+        if (cleanup) {
+            vhost_net_cleanup(s->vhost_net);
+        }
+    }
+}
+
+static void vhost_user_stop(int queues, NetClientState *ncs[])
+{
     int i;

     for (i = 0; i < queues; i++) {
         assert(ncs[i]->info->type == NET_CLIENT_DRIVER_VHOST_USER);

-        s = DO_UPCAST(NetVhostUserState, nc, ncs[i]);
-
-        if (s->vhost_net) {
-            /* save acked features */
-            uint64_t features = vhost_net_get_acked_features(s->vhost_net);
-            if (features) {
-                s->acked_features = features;
-            }
-            vhost_net_cleanup(s->vhost_net);
-        }
+        vhost_user_save_acked_features(ncs[i], true);
     }
 }

@@ -251,11 +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);
--
2.27.0