[Qemu-devel] [PATCH 00/10] RFCv3: vhost-user: simple reconnection support

[Qemu-devel] [PATCH 00/10] RFCv3: vhost-user: simple reconnection support

[marcandre.lureau]

From: Marc-André Lureau <marcandre.lureau@redhat.com>

Hi,

In a previous series "RFCv2: vhost-user: shutdown and reconnection", I
proposed to add a new slave request to handle graceful shutdown, for
both qemu configuration, server or client, while keeping the guest
running with link down status.

However, for the simple case where qemu is configured as server, and
the backend processes packets in order and disconnects, it is possible
for the backend to recover after reconnection by discarding the qemu
SET_VRING_BASE value and resuming from the used->index instead. This
simplifies the reconnection support in this particular situation (it
would make sense to have the backend declare this behaviour with an
extra flag)

The guest won't be notified of link status change and queues may not
be processed in a timely manner, also qemu may assert if some
vhost-user commands are happening while the backend is disconnected.
So the reconnection must happen "quickly enough" here. In order to
keep the series relatively small, these further problems will be
addressed later.

These series demonstrates a simple reconnect support for vubr
(configured as client and qemu as server), includes some nice to
have fixes and a simple test.

Marc-André Lureau (8):
  vubr: add client mode
  vubr: workaround stale vring base
  vhost-user: disconnect on start failure
  vhost-net: do not crash if backend is not present
  vhost-net: save & restore vhost-user acked features
  vhost-net: save & restore vring enable state
  tests: append i386 tests
  test: start vhost-user reconnect test

Tetsuya Mukawa (2):
  vhost-user: add ability to know vhost-user backend disconnection
  qemu-char: add qemu_chr_disconnect to close a fd accepted by listen fd

 hw/net/vhost_net.c        |  39 ++++++++++++++-
 include/net/net.h         |   1 +
 include/net/vhost-user.h  |   1 +
 include/net/vhost_net.h   |   3 ++
 include/sysemu/char.h     |   7 +++
 net/vhost-user.c          |  32 +++++++++++-
 qemu-char.c               |   8 +++
 tests/Makefile            |   2 +-
 tests/vhost-user-bridge.c |  45 ++++++++++++-----
 tests/vhost-user-test.c   | 123 +++++++++++++++++++++++++++++++++++++++-------
 10 files changed, 228 insertions(+), 33 deletions(-)

-- 
2.7.4

[Qemu-devel] [PATCH 01/10] vhost-user: add ability to know vhost-user backend disconnection

[marcandre.lureau]

From: Tetsuya Mukawa <mukawa@igel.co.jp>

Current QEMU cannot detect vhost-user backend disconnection. The
patch adds ability to know it.
To know disconnection, add watcher to detect G_IO_HUP event. When
G_IO_HUP event is detected, the disconnected socket will be read
to cause a CHR_EVENT_CLOSED.

Signed-off-by: Tetsuya Mukawa <mukawa@igel.co.jp>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
---
 net/vhost-user.c | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/net/vhost-user.c b/net/vhost-user.c
index 1b9e73a..4a7fd5f 100644
--- a/net/vhost-user.c
+++ b/net/vhost-user.c
@@ -22,6 +22,7 @@ typedef struct VhostUserState {
     NetClientState nc;
     CharDriverState *chr;
     VHostNetState *vhost_net;
+    int watch;
 } VhostUserState;
 
 typedef struct VhostUserChardevProps {
@@ -167,6 +168,20 @@ static NetClientInfo net_vhost_user_info = {
         .has_ufo = vhost_user_has_ufo,
 };
 
+static gboolean net_vhost_user_watch(GIOChannel *chan, GIOCondition cond,
+                                           void *opaque)
+{
+    VhostUserState *s = opaque;
+    uint8_t buf[1];
+
+    /* We don't actually want to read anything, but CHR_EVENT_CLOSED will be
+     * raised as a side-effect of the read.
+     */
+    qemu_chr_fe_read_all(s->chr, buf, sizeof(buf));
+
+    return FALSE;
+}
+
 static void net_vhost_user_event(void *opaque, int event)
 {
     const char *name = opaque;
@@ -184,6 +199,8 @@ static void net_vhost_user_event(void *opaque, int event)
     trace_vhost_user_event(s->chr->label, event);
     switch (event) {
     case CHR_EVENT_OPENED:
+        s->watch = qemu_chr_fe_add_watch(s->chr, G_IO_HUP,
+                                         net_vhost_user_watch, s);
         if (vhost_user_start(queues, ncs) < 0) {
             exit(1);
         }
@@ -192,6 +209,8 @@ static void net_vhost_user_event(void *opaque, int event)
     case CHR_EVENT_CLOSED:
         qmp_set_link(name, false, &err);
         vhost_user_stop(queues, ncs);
+        g_source_remove(s->watch);
+        s->watch = 0;
         break;
     }
 
-- 
2.7.4

[Qemu-devel] [PATCH 02/10] vubr: add client mode

[marcandre.lureau]

From: Marc-André Lureau <marcandre.lureau@redhat.com>

If -c is specified, vubr will try to connect to the socket instead of
listening for connections.

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
---
 tests/vhost-user-bridge.c | 38 ++++++++++++++++++++++++++------------
 1 file changed, 26 insertions(+), 12 deletions(-)

diff --git a/tests/vhost-user-bridge.c b/tests/vhost-user-bridge.c
index 0779ba2..f907ce7 100644
--- a/tests/vhost-user-bridge.c
+++ b/tests/vhost-user-bridge.c
@@ -1204,12 +1204,13 @@ vubr_accept_cb(int sock, void *ctx)
 }
 
 static VubrDev *
-vubr_new(const char *path)
+vubr_new(const char *path, bool client)
 {
     VubrDev *dev = (VubrDev *) calloc(1, sizeof(VubrDev));
     dev->nregions = 0;
     int i;
     struct sockaddr_un un;
+    CallbackFunc cb;
     size_t len;
 
     for (i = 0; i < MAX_NR_VIRTQUEUE; i++) {
@@ -1238,19 +1239,27 @@ vubr_new(const char *path)
     un.sun_family = AF_UNIX;
     strcpy(un.sun_path, path);
     len = sizeof(un.sun_family) + strlen(path);
-    unlink(path);
 
-    if (bind(dev->sock, (struct sockaddr *) &un, len) == -1) {
-        vubr_die("bind");
-    }
+    if (!client) {
+        unlink(path);
+
+        if (bind(dev->sock, (struct sockaddr *) &un, len) == -1) {
+            vubr_die("bind");
+        }
 
-    if (listen(dev->sock, 1) == -1) {
-        vubr_die("listen");
+        if (listen(dev->sock, 1) == -1) {
+            vubr_die("listen");
+        }
+        cb = vubr_accept_cb;
+    } else {
+        if (connect(dev->sock, (struct sockaddr *)&un, len) == -1) {
+            vubr_die("connect");
+        }
+        cb = vubr_receive_cb;
     }
 
     dispatcher_init(&dev->dispatcher);
-    dispatcher_add(&dev->dispatcher, dev->sock, (void *)dev,
-                   vubr_accept_cb);
+    dispatcher_add(&dev->dispatcher, dev->sock, (void *)dev, cb);
 
     DPRINT("Waiting for connections on UNIX socket %s ...\n", path);
     return dev;
@@ -1369,8 +1378,9 @@ main(int argc, char *argv[])
 {
     VubrDev *dev;
     int opt;
+    bool client = false;
 
-    while ((opt = getopt(argc, argv, "l:r:u:")) != -1) {
+    while ((opt = getopt(argc, argv, "l:r:u:c")) != -1) {
 
         switch (opt) {
         case 'l':
@@ -1386,16 +1396,20 @@ main(int argc, char *argv[])
         case 'u':
             ud_socket_path = strdup(optarg);
             break;
+        case 'c':
+            client = true;
+            break;
         default:
             goto out;
         }
     }
 
-    DPRINT("ud socket: %s\n", ud_socket_path);
+    DPRINT("ud socket: %s (%s)\n", ud_socket_path,
+           client ? "client" : "server");
     DPRINT("local:     %s:%s\n", lhost, lport);
     DPRINT("remote:    %s:%s\n", rhost, rport);
 
-    dev = vubr_new(ud_socket_path);
+    dev = vubr_new(ud_socket_path, client);
     if (!dev) {
         return 1;
     }
-- 
2.7.4

Re: [Qemu-devel] [PATCH 02/10] vubr: add client mode

[Yuanhan Liu]

Hi,

Just to let you know that as a client, it need to add the reconnect
ability, as the QEMU (as the server) may restart as well. Well, I'm
thinking that you may think it's an example bridge only, so, let it
be simple. Then I'm sorry for the noise.

	--yliu

On Tue, May 10, 2016 at 06:03:52PM +0200, marcandre.lureau@redhat.com wrote:
> From: Marc-André Lureau <marcandre.lureau@redhat.com>
> 
> If -c is specified, vubr will try to connect to the socket instead of
> listening for connections.
> 
> Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
> ---
>  tests/vhost-user-bridge.c | 38 ++++++++++++++++++++++++++------------
>  1 file changed, 26 insertions(+), 12 deletions(-)
> 
> diff --git a/tests/vhost-user-bridge.c b/tests/vhost-user-bridge.c
> index 0779ba2..f907ce7 100644
> --- a/tests/vhost-user-bridge.c
> +++ b/tests/vhost-user-bridge.c
> @@ -1204,12 +1204,13 @@ vubr_accept_cb(int sock, void *ctx)
>  }
>  
>  static VubrDev *
> -vubr_new(const char *path)
> +vubr_new(const char *path, bool client)
>  {
>      VubrDev *dev = (VubrDev *) calloc(1, sizeof(VubrDev));
>      dev->nregions = 0;
>      int i;
>      struct sockaddr_un un;
> +    CallbackFunc cb;
>      size_t len;
>  
>      for (i = 0; i < MAX_NR_VIRTQUEUE; i++) {
> @@ -1238,19 +1239,27 @@ vubr_new(const char *path)
>      un.sun_family = AF_UNIX;
>      strcpy(un.sun_path, path);
>      len = sizeof(un.sun_family) + strlen(path);
> -    unlink(path);
>  
> -    if (bind(dev->sock, (struct sockaddr *) &un, len) == -1) {
> -        vubr_die("bind");
> -    }
> +    if (!client) {
> +        unlink(path);
> +
> +        if (bind(dev->sock, (struct sockaddr *) &un, len) == -1) {
> +            vubr_die("bind");
> +        }
>  
> -    if (listen(dev->sock, 1) == -1) {
> -        vubr_die("listen");
> +        if (listen(dev->sock, 1) == -1) {
> +            vubr_die("listen");
> +        }
> +        cb = vubr_accept_cb;
> +    } else {
> +        if (connect(dev->sock, (struct sockaddr *)&un, len) == -1) {
> +            vubr_die("connect");
> +        }
> +        cb = vubr_receive_cb;
>      }
>  
>      dispatcher_init(&dev->dispatcher);
> -    dispatcher_add(&dev->dispatcher, dev->sock, (void *)dev,
> -                   vubr_accept_cb);
> +    dispatcher_add(&dev->dispatcher, dev->sock, (void *)dev, cb);
>  
>      DPRINT("Waiting for connections on UNIX socket %s ...\n", path);
>      return dev;
> @@ -1369,8 +1378,9 @@ main(int argc, char *argv[])
>  {
>      VubrDev *dev;
>      int opt;
> +    bool client = false;
>  
> -    while ((opt = getopt(argc, argv, "l:r:u:")) != -1) {
> +    while ((opt = getopt(argc, argv, "l:r:u:c")) != -1) {
>  
>          switch (opt) {
>          case 'l':
> @@ -1386,16 +1396,20 @@ main(int argc, char *argv[])
>          case 'u':
>              ud_socket_path = strdup(optarg);
>              break;
> +        case 'c':
> +            client = true;
> +            break;
>          default:
>              goto out;
>          }
>      }
>  
> -    DPRINT("ud socket: %s\n", ud_socket_path);
> +    DPRINT("ud socket: %s (%s)\n", ud_socket_path,
> +           client ? "client" : "server");
>      DPRINT("local:     %s:%s\n", lhost, lport);
>      DPRINT("remote:    %s:%s\n", rhost, rport);
>  
> -    dev = vubr_new(ud_socket_path);
> +    dev = vubr_new(ud_socket_path, client);
>      if (!dev) {
>          return 1;
>      }
> -- 
> 2.7.4

Re: [Qemu-devel] [PATCH 02/10] vubr: add client mode

[Marc-André Lureau]

Hi

----- Original Message -----
> Hi,
> 
> Just to let you know that as a client, it need to add the reconnect
> ability, as the QEMU (as the server) may restart as well. Well, I'm
> thinking that you may think it's an example bridge only, so, let it
> be simple. Then I'm sorry for the noise.

That's a different use case to me, and a separate possible addition to vubr.

thanks

[Qemu-devel] [PATCH 03/10] vubr: workaround stale vring base

[marcandre.lureau]

From: Marc-André Lureau <marcandre.lureau@redhat.com>

This patch is a similar solution to what Yuanhan Liu/Huawei Xie have
suggested for DPDK. When vubr quits (killed or crashed), a restart of
vubr would get stale vring base from QEMU. That would break the kernel
virtio net completely, making it non-work any more, unless a driver
reset is done.

So, instead of getting the stale vring base from QEMU, Huawei suggested
we could get a proper one from used->idx. This works because the queues
packets are processed in order.

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
---
 tests/vhost-user-bridge.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/tests/vhost-user-bridge.c b/tests/vhost-user-bridge.c
index f907ce7..38963e4 100644
--- a/tests/vhost-user-bridge.c
+++ b/tests/vhost-user-bridge.c
@@ -946,6 +946,13 @@ vubr_set_vring_addr_exec(VubrDev *dev, VhostUserMsg *vmsg)
     DPRINT("    vring_avail at %p\n", vq->avail);
 
     vq->last_used_index = vq->used->idx;
+
+    if (vq->last_avail_index != vq->used->idx) {
+        DPRINT("Last avail index != used index: %d != %d, resuming",
+               vq->last_avail_index, vq->used->idx);
+        vq->last_avail_index = vq->used->idx;
+    }
+
     return 0;
 }
 
-- 
2.7.4

[Qemu-devel] [PATCH 04/10] qemu-char: add qemu_chr_disconnect to close a fd accepted by listen fd

[marcandre.lureau]

From: Tetsuya Mukawa <mukawa@igel.co.jp>

The patch introduces qemu_chr_disconnect(). The function is used for
closing a fd accepted by listen fd. Though we already have qemu_chr_delete(),
but it closes not only accepted fd but also listen fd. This new function
is used when we still want to keep listen fd.

Signed-off-by: Tetsuya Mukawa <mukawa@igel.co.jp>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
---
 include/sysemu/char.h | 7 +++++++
 qemu-char.c           | 8 ++++++++
 2 files changed, 15 insertions(+)

diff --git a/include/sysemu/char.h b/include/sysemu/char.h
index 307fd8f..2c39987 100644
--- a/include/sysemu/char.h
+++ b/include/sysemu/char.h
@@ -75,6 +75,7 @@ struct CharDriverState {
     IOReadHandler *chr_read;
     void *handler_opaque;
     void (*chr_close)(struct CharDriverState *chr);
+    void (*chr_disconnect)(struct CharDriverState *chr);
     void (*chr_accept_input)(struct CharDriverState *chr);
     void (*chr_set_echo)(struct CharDriverState *chr, bool echo);
     void (*chr_set_fe_open)(struct CharDriverState *chr, int fe_open);
@@ -143,6 +144,12 @@ void qemu_chr_parse_common(QemuOpts *opts, ChardevCommon *backend);
  */
 CharDriverState *qemu_chr_new(const char *label, const char *filename,
                               void (*init)(struct CharDriverState *s));
+/**
+ * @qemu_chr_disconnect:
+ *
+ * Close a fd accpeted by character backend.
+ */
+void qemu_chr_disconnect(CharDriverState *chr);
 
 /**
  * @qemu_chr_new_noreplay:
diff --git a/qemu-char.c b/qemu-char.c
index b597ee1..6efbc0d 100644
--- a/qemu-char.c
+++ b/qemu-char.c
@@ -4012,6 +4012,13 @@ void qemu_chr_fe_release(CharDriverState *s)
     s->avail_connections++;
 }
 
+void qemu_chr_disconnect(CharDriverState *chr)
+{
+    if (chr->chr_disconnect) {
+        chr->chr_disconnect(chr);
+    }
+}
+
 static void qemu_chr_free_common(CharDriverState *chr)
 {
     g_free(chr->filename);
@@ -4405,6 +4412,7 @@ static CharDriverState *qmp_chardev_open_socket(const char *id,
     chr->chr_write = tcp_chr_write;
     chr->chr_sync_read = tcp_chr_sync_read;
     chr->chr_close = tcp_chr_close;
+    chr->chr_disconnect = tcp_chr_disconnect;
     chr->get_msgfds = tcp_get_msgfds;
     chr->set_msgfds = tcp_set_msgfds;
     chr->chr_add_client = tcp_chr_add_client;
-- 
2.7.4

[Qemu-devel] [PATCH 05/10] vhost-user: disconnect on start failure

[marcandre.lureau]

From: Marc-André Lureau <marcandre.lureau@redhat.com>

If the backend failed to start (for example feature negociation failed),
do not exit, but disconnect the char device instead. Slightly more
robust for reconnect case.

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
---
 net/vhost-user.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/vhost-user.c b/net/vhost-user.c
index 4a7fd5f..41ddb4b 100644
--- a/net/vhost-user.c
+++ b/net/vhost-user.c
@@ -202,7 +202,8 @@ static void net_vhost_user_event(void *opaque, int event)
         s->watch = qemu_chr_fe_add_watch(s->chr, G_IO_HUP,
                                          net_vhost_user_watch, s);
         if (vhost_user_start(queues, ncs) < 0) {
-            exit(1);
+            qemu_chr_disconnect(s->chr);
+            return;
         }
         qmp_set_link(name, true, &err);
         break;
-- 
2.7.4

[Qemu-devel] [PATCH 06/10] vhost-net: do not crash if backend is not present

[marcandre.lureau]

From: Marc-André Lureau <marcandre.lureau@redhat.com>

Do not crash when backend is not present while enabling the ring. A
following patch will save the enabled state so it can be restored once
the backend is started.

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
---
 hw/net/vhost_net.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/hw/net/vhost_net.c b/hw/net/vhost_net.c
index 6e1032f..805a0df 100644
--- a/hw/net/vhost_net.c
+++ b/hw/net/vhost_net.c
@@ -401,8 +401,13 @@ VHostNetState *get_vhost_net(NetClientState *nc)
 int vhost_set_vring_enable(NetClientState *nc, int enable)
 {
     VHostNetState *net = get_vhost_net(nc);
-    const VhostOps *vhost_ops = net->dev.vhost_ops;
+    const VhostOps *vhost_ops;
+
+    if (!net) {
+        return 0;
+    }
 
+    vhost_ops = net->dev.vhost_ops;
     if (vhost_ops->vhost_set_vring_enable) {
         return vhost_ops->vhost_set_vring_enable(&net->dev, enable);
     }
-- 
2.7.4

[Qemu-devel] [PATCH 07/10] vhost-net: save & restore vhost-user acked features

[marcandre.lureau]

From: Marc-André Lureau <marcandre.lureau@redhat.com>

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 <marcandre.lureau@redhat.com>
---
 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 805a0df..f3df18c 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) {
@@ -136,6 +141,7 @@ 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");
@@ -183,8 +189,21 @@ 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 41ddb4b..d72ce9b 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 {
@@ -37,6 +38,13 @@ 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;
@@ -56,6 +64,8 @@ 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;
         }
-- 
2.7.4

Re: [Qemu-devel] [PATCH 07/10] vhost-net: save & restore vhost-user acked features

[Yuanhan Liu]

On Tue, May 10, 2016 at 06:03:57PM +0200, marcandre.lureau@redhat.com wrote:
> From: Marc-André Lureau <marcandre.lureau@redhat.com>
> 
> 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 <marcandre.lureau@redhat.com>
> ---
>  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 805a0df..f3df18c 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;
> +}

Note that you need add a dummy implementation for !VHOST_NET. Otherwise,
build won't work.

And sorry for being noisy, here is another ping about the status of
this patch set.

	--yliu

Re: [Qemu-devel] [PATCH 07/10] vhost-net: save & restore vhost-user acked features

[Marc-André Lureau]

Hi

----- Original Message -----
> > +uint64_t vhost_net_get_acked_features(VHostNetState *net)
> > +{
> > +    return net->dev.acked_features;
> > +}
> 
> Note that you need add a dummy implementation for !VHOST_NET. Otherwise,
> build won't work.

good catch, fixed.

> And sorry for being noisy, here is another ping about the status of
> this patch set.

thanks

[Qemu-devel] [PATCH 08/10] vhost-net: save & restore vring enable state

[marcandre.lureau]

From: Marc-André Lureau <marcandre.lureau@redhat.com>

A driver may change the vring enable state at run time but vhost-user
backend may not be present (a contrived example is when the backend is
disconnected and the device is reconfigured after driver rebinding)

Restore the vring state when the vhost-user backend is started, so it
can process the ring.

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
---
 hw/net/vhost_net.c | 11 +++++++++++
 include/net/net.h  |  1 +
 2 files changed, 12 insertions(+)

diff --git a/hw/net/vhost_net.c b/hw/net/vhost_net.c
index f3df18c..722e3f3 100644
--- a/hw/net/vhost_net.c
+++ b/hw/net/vhost_net.c
@@ -329,6 +329,15 @@ int vhost_net_start(VirtIODevice *dev, NetClientState *ncs,
         if (r < 0) {
             goto err_start;
         }
+
+        if (ncs[i].peer->vring_enable) {
+            /* restore vring enable state */
+            r = vhost_set_vring_enable(ncs[i].peer, ncs[i].peer->vring_enable);
+
+            if (r < 0) {
+                goto err_start;
+            }
+        }
     }
 
     return 0;
@@ -422,6 +431,8 @@ int vhost_set_vring_enable(NetClientState *nc, int enable)
     VHostNetState *net = get_vhost_net(nc);
     const VhostOps *vhost_ops;
 
+    nc->vring_enable = enable;
+
     if (!net) {
         return 0;
     }
diff --git a/include/net/net.h b/include/net/net.h
index 73e4c46..2c4b23a 100644
--- a/include/net/net.h
+++ b/include/net/net.h
@@ -92,6 +92,7 @@ struct NetClientState {
     NetClientDestructor *destructor;
     unsigned int queue_index;
     unsigned rxfilter_notify_enabled:1;
+    int vring_enable;
     QTAILQ_HEAD(NetFilterHead, NetFilterState) filters;
 };
 
-- 
2.7.4

[Qemu-devel] [PATCH 09/10] tests: append i386 tests

[marcandre.lureau]

From: Marc-André Lureau <marcandre.lureau@redhat.com>

Do not overwrite x86-64 tests, re-enable vhost-user-test.

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
---
 tests/Makefile | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tests/Makefile b/tests/Makefile
index 9194f18..50a99f8 100644
--- a/tests/Makefile
+++ b/tests/Makefile
@@ -224,7 +224,7 @@ endif
 check-qtest-i386-y += tests/test-netfilter$(EXESUF)
 check-qtest-i386-y += tests/test-filter-mirror$(EXESUF)
 check-qtest-i386-y += tests/test-filter-redirector$(EXESUF)
-check-qtest-x86_64-y = $(check-qtest-i386-y)
+check-qtest-x86_64-y += $(check-qtest-i386-y)
 gcov-files-i386-y += i386-softmmu/hw/timer/mc146818rtc.c
 gcov-files-x86_64-y = $(subst i386-softmmu/,x86_64-softmmu/,$(gcov-files-i386-y))
 check-qtest-mips-y = tests/endianness-test$(EXESUF)
-- 
2.7.4

[Qemu-devel] [PATCH 10/10] test: start vhost-user reconnect test

[marcandre.lureau]

From: Marc-André Lureau <marcandre.lureau@redhat.com>

This is a simple reconnect test, that simply checks if vhost-user
reconnection is possible and restore the state. A more complete test
would actually manipulate and check the ring contents (such extended
testing would benefit from the libvhost-user proposed in QEMU list to
avoid duplication of ring manipulations)

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
---
 tests/vhost-user-test.c | 123 +++++++++++++++++++++++++++++++++++++++++-------
 1 file changed, 106 insertions(+), 17 deletions(-)

diff --git a/tests/vhost-user-test.c b/tests/vhost-user-test.c
index 6961596..1734a2b 100644
--- a/tests/vhost-user-test.c
+++ b/tests/vhost-user-test.c
@@ -34,7 +34,7 @@
 #define QEMU_CMD_ACCEL  " -machine accel=tcg"
 #define QEMU_CMD_MEM    " -m %d -object memory-backend-file,id=mem,size=%dM,"\
                         "mem-path=%s,share=on -numa node,memdev=mem"
-#define QEMU_CMD_CHR    " -chardev socket,id=%s,path=%s"
+#define QEMU_CMD_CHR    " -chardev socket,id=%s,path=%s%s"
 #define QEMU_CMD_NETDEV " -netdev vhost-user,id=net0,chardev=%s,vhostforce"
 #define QEMU_CMD_NET    " -device virtio-net-pci,netdev=net0,romfile=./pc-bios/pxe-virtio.rom"
 
@@ -246,7 +246,12 @@ static void chr_read(void *opaque, const uint8_t *buf, int size)
 
     if (msg.size) {
         p += VHOST_USER_HDR_SIZE;
-        g_assert_cmpint(qemu_chr_fe_read_all(chr, p, msg.size), ==, msg.size);
+        size = qemu_chr_fe_read_all(chr, p, msg.size);
+        if (size != msg.size) {
+            g_test_message("Wrong message size received %d != %d\n",
+                           size, msg.size);
+            return;
+        }
     }
 
     switch (msg.request) {
@@ -363,17 +368,10 @@ static const char *init_hugepagefs(const char *path)
 static TestServer *test_server_new(const gchar *name)
 {
     TestServer *server = g_new0(TestServer, 1);
-    gchar *chr_path;
 
     server->socket_path = g_strdup_printf("%s/%s.sock", tmpfs, name);
     server->mig_path = g_strdup_printf("%s/%s.mig", tmpfs, name);
-
-    chr_path = g_strdup_printf("unix:%s,server,nowait", server->socket_path);
     server->chr_name = g_strdup_printf("chr-%s", name);
-    server->chr = qemu_chr_new(server->chr_name, chr_path, NULL);
-    g_free(chr_path);
-
-    qemu_chr_add_handlers(server->chr, chr_can_read, chr_read, NULL, server);
 
     g_mutex_init(&server->data_mutex);
     g_cond_init(&server->data_cond);
@@ -383,13 +381,34 @@ static TestServer *test_server_new(const gchar *name)
     return server;
 }
 
-#define GET_QEMU_CMD(s)                                                        \
-    g_strdup_printf(QEMU_CMD, 512, 512, (root), (s)->chr_name,                 \
-                    (s)->socket_path, (s)->chr_name)
+static void test_server_create_chr(TestServer *server, const gchar *opt)
+{
+    gchar *chr_path;
+
+    chr_path = g_strdup_printf("unix:%s%s", server->socket_path, opt);
+    server->chr = qemu_chr_new(server->chr_name, chr_path, NULL);
+    g_free(chr_path);
 
-#define GET_QEMU_CMDE(s, mem, extra, ...)                                      \
-    g_strdup_printf(QEMU_CMD extra, (mem), (mem), (root), (s)->chr_name,       \
-                    (s)->socket_path, (s)->chr_name, ##__VA_ARGS__)
+    qemu_chr_add_handlers(server->chr, chr_can_read, chr_read, NULL, server);
+}
+
+static void test_server_listen(TestServer *server)
+{
+    test_server_create_chr(server, ",server,nowait");
+}
+
+static void test_server_connect(TestServer *server)
+{
+    test_server_create_chr(server, ",reconnect=1");
+}
+
+#define GET_QEMU_CMD(s)                                         \
+    g_strdup_printf(QEMU_CMD, 512, 512, (root), (s)->chr_name,  \
+                    (s)->socket_path, "", (s)->chr_name)
+
+#define GET_QEMU_CMDE(s, mem, chr_opts, extra, ...)                     \
+    g_strdup_printf(QEMU_CMD extra, (mem), (mem), (root), (s)->chr_name, \
+                    (s)->socket_path, (chr_opts), (s)->chr_name, ##__VA_ARGS__)
 
 static gboolean _test_server_free(TestServer *server)
 {
@@ -537,7 +556,10 @@ static void test_migrate(void)
     guint8 *log;
     guint64 size;
 
-    cmd = GET_QEMU_CMDE(s, 2, "");
+    test_server_listen(s);
+    test_server_listen(dest);
+
+    cmd = GET_QEMU_CMDE(s, 2, "", "");
     from = qtest_start(cmd);
     g_free(cmd);
 
@@ -545,7 +567,7 @@ static void test_migrate(void)
     size = get_log_size(s);
     g_assert_cmpint(size, ==, (2 * 1024 * 1024) / (VHOST_LOG_PAGE * 8));
 
-    cmd = GET_QEMU_CMDE(dest, 2, " -incoming %s", uri);
+    cmd = GET_QEMU_CMDE(dest, 2, "", " -incoming %s", uri);
     to = qtest_init(cmd);
     g_free(cmd);
 
@@ -605,6 +627,71 @@ static void test_migrate(void)
     global_qtest = global;
 }
 
+static void wait_for_rings_started(TestServer *s, size_t count)
+{
+    gint64 end_time;
+
+    g_mutex_lock(&s->data_mutex);
+    end_time = g_get_monotonic_time() + 5 * G_TIME_SPAN_SECOND;
+    while (ctpop64(s->rings) != count) {
+        if (!g_cond_wait_until(&s->data_cond, &s->data_mutex, end_time)) {
+            /* timeout has passed */
+            g_assert_cmpint(ctpop64(s->rings), ==, count);
+            break;
+        }
+    }
+
+    g_mutex_unlock(&s->data_mutex);
+}
+
+static gboolean
+reconnect_cb(gpointer user_data)
+{
+    TestServer *s = user_data;
+
+    qemu_chr_disconnect(s->chr);
+
+    return FALSE;
+}
+
+#define PCI_SLOT                0x04
+
+static gpointer
+connect_thread(gpointer data)
+{
+    TestServer *s = data;
+
+    /* wait for qemu to start before first try, to avoid extra warnings */
+    g_usleep(G_USEC_PER_SEC);
+    test_server_connect(s);
+
+    return NULL;
+}
+
+static void test_reconnect(void)
+{
+    TestServer *s = test_server_new("reconnect");
+    char *cmd;
+
+    g_thread_new("connect", connect_thread, s);
+    cmd = GET_QEMU_CMDE(s, 2, ",server", "");
+    qtest_start(cmd);
+    g_free(cmd);
+
+    wait_for_fds(s);
+    wait_for_rings_started(s, 2);
+
+    /* reconnect */
+    s->fds_num = 0;
+    s->rings = 0;
+    g_idle_add(reconnect_cb, s);
+    wait_for_fds(s);
+    wait_for_rings_started(s, 2);
+
+    qtest_end();
+    test_server_free(s);
+}
+
 int main(int argc, char **argv)
 {
     QTestState *s = NULL;
@@ -636,6 +723,7 @@ int main(int argc, char **argv)
     }
 
     server = test_server_new("test");
+    test_server_listen(server);
 
     loop = g_main_loop_new(NULL, FALSE);
     /* run the main loop thread so the chardev may operate */
@@ -648,6 +736,7 @@ int main(int argc, char **argv)
 
     qtest_add_data_func("/vhost-user/read-guest-mem", server, read_guest_mem);
     qtest_add_func("/vhost-user/migrate", test_migrate);
+    qtest_add_func("/vhost-user/reconnect", test_reconnect);
 
     ret = g_test_run();
 
-- 
2.7.4

Re: [Qemu-devel] [PATCH 00/10] RFCv3: vhost-user: simple reconnection support

[Michael S. Tsirkin]

On Tue, May 10, 2016 at 06:03:50PM +0200, marcandre.lureau@redhat.com wrote:
> From: Marc-André Lureau <marcandre.lureau@redhat.com>
> 
> Hi,
> 
> In a previous series "RFCv2: vhost-user: shutdown and reconnection", I
> proposed to add a new slave request to handle graceful shutdown, for
> both qemu configuration, server or client, while keeping the guest
> running with link down status.

OK so I would say patches 1-4 are bugfixes, looks like they
can be Cc stable even?


> However, for the simple case where qemu is configured as server, and
> the backend processes packets in order and disconnects, it is possible
> for the backend to recover after reconnection by discarding the qemu
> SET_VRING_BASE value and resuming from the used->index instead. This
> simplifies the reconnection support in this particular situation (it
> would make sense to have the backend declare this behaviour with an
> extra flag)
> 
> The guest won't be notified of link status change and queues may not
> be processed in a timely manner, also qemu may assert if some
> vhost-user commands are happening while the backend is disconnected.
> So the reconnection must happen "quickly enough" here. In order to
> keep the series relatively small, these further problems will be
> addressed later.
> 
> These series demonstrates a simple reconnect support for vubr
> (configured as client and qemu as server), includes some nice to
> have fixes and a simple test.
> 
> Marc-André Lureau (8):
>   vubr: add client mode
>   vubr: workaround stale vring base
>   vhost-user: disconnect on start failure
>   vhost-net: do not crash if backend is not present
>   vhost-net: save & restore vhost-user acked features
>   vhost-net: save & restore vring enable state
>   tests: append i386 tests
>   test: start vhost-user reconnect test
> 
> Tetsuya Mukawa (2):
>   vhost-user: add ability to know vhost-user backend disconnection
>   qemu-char: add qemu_chr_disconnect to close a fd accepted by listen fd
> 
>  hw/net/vhost_net.c        |  39 ++++++++++++++-
>  include/net/net.h         |   1 +
>  include/net/vhost-user.h  |   1 +
>  include/net/vhost_net.h   |   3 ++
>  include/sysemu/char.h     |   7 +++
>  net/vhost-user.c          |  32 +++++++++++-
>  qemu-char.c               |   8 +++
>  tests/Makefile            |   2 +-
>  tests/vhost-user-bridge.c |  45 ++++++++++++-----
>  tests/vhost-user-test.c   | 123 +++++++++++++++++++++++++++++++++++++++-------
>  10 files changed, 228 insertions(+), 33 deletions(-)
> 
> -- 
> 2.7.4

Re: [Qemu-devel] [PATCH 00/10] RFCv3: vhost-user: simple reconnection support

[Marc-André Lureau]

Hi

----- Original Message -----
> On Tue, May 10, 2016 at 06:03:50PM +0200, marcandre.lureau@redhat.com wrote:
> > From: Marc-André Lureau <marcandre.lureau@redhat.com>
> > 
> > Hi,
> > 
> > In a previous series "RFCv2: vhost-user: shutdown and reconnection", I
> > proposed to add a new slave request to handle graceful shutdown, for
> > both qemu configuration, server or client, while keeping the guest
> > running with link down status.
> 
> OK so I would say patches 1-4 are bugfixes, looks like they
> can be Cc stable even?

4 is being used by 5 and 10.
2-3 are only for testing.

4-8 are nice to have as they avoid obvious problems/crashes when handling disconnected state and add basic reconnection checks.

9 was already considered for stable by Eric in a previous series

10 would be good to have if 1 is accepted, to check the minimum works as expected

Re: [Qemu-devel] [PATCH 00/10] RFCv3: vhost-user: simple reconnection support

[Marc-André Lureau]

Hi

On Tue, May 10, 2016 at 6:28 PM, Marc-André Lureau <mlureau@redhat.com> wrote:
> Hi
>
> ----- Original Message -----
>> On Tue, May 10, 2016 at 06:03:50PM +0200, marcandre.lureau@redhat.com wrote:
>> > From: Marc-André Lureau <marcandre.lureau@redhat.com>
>> >
>> > Hi,
>> >
>> > In a previous series "RFCv2: vhost-user: shutdown and reconnection", I
>> > proposed to add a new slave request to handle graceful shutdown, for
>> > both qemu configuration, server or client, while keeping the guest
>> > running with link down status.
>>
>> OK so I would say patches 1-4 are bugfixes, looks like they
>> can be Cc stable even?
>
> 4 is being used by 5 and 10.
> 2-3 are only for testing.
>
> 4-8 are nice to have as they avoid obvious problems/crashes when handling disconnected state and add basic reconnection checks.
>
> 9 was already considered for stable by Eric in a previous series
>
> 10 would be good to have if 1 is accepted, to check the minimum works as expected
>

FYI, I have a follow up series (~20 patches,
https://github.com/elmarco/qemu/tree/vhost-user-reconnect) doing
mostly cleanups and extra checks for disconnection at run time. In
particular, it should avoid some obvious crashers/asserts, and
prevents qemu from running as long the initial vhost_user_start()
didn't succeed (so initial flags are set). I would like to know how to
proceed with the follow-up: should I resend the whole series or should
we review/merge this rfc first (even though it is known to be
incomplete in many disconnect cases that the follow up fixes).

thanks

-- 
Marc-André Lureau

Re: [Qemu-devel] [PATCH 00/10] RFCv3: vhost-user: simple reconnection support

[Michael S. Tsirkin]

On Fri, May 13, 2016 at 08:30:36PM +0200, Marc-André Lureau wrote:
> Hi
> 
> On Tue, May 10, 2016 at 6:28 PM, Marc-André Lureau <mlureau@redhat.com> wrote:
> > Hi
> >
> > ----- Original Message -----
> >> On Tue, May 10, 2016 at 06:03:50PM +0200, marcandre.lureau@redhat.com wrote:
> >> > From: Marc-André Lureau <marcandre.lureau@redhat.com>
> >> >
> >> > Hi,
> >> >
> >> > In a previous series "RFCv2: vhost-user: shutdown and reconnection", I
> >> > proposed to add a new slave request to handle graceful shutdown, for
> >> > both qemu configuration, server or client, while keeping the guest
> >> > running with link down status.
> >>
> >> OK so I would say patches 1-4 are bugfixes, looks like they
> >> can be Cc stable even?
> >
> > 4 is being used by 5 and 10.
> > 2-3 are only for testing.
> >
> > 4-8 are nice to have as they avoid obvious problems/crashes when handling disconnected state and add basic reconnection checks.
> >
> > 9 was already considered for stable by Eric in a previous series
> >
> > 10 would be good to have if 1 is accepted, to check the minimum works as expected
> >
> 
> FYI, I have a follow up series (~20 patches,
> https://github.com/elmarco/qemu/tree/vhost-user-reconnect) doing
> mostly cleanups and extra checks for disconnection at run time. In
> particular, it should avoid some obvious crashers/asserts, and
> prevents qemu from running as long the initial vhost_user_start()
> didn't succeed (so initial flags are set). I would like to know how to
> proceed with the follow-up: should I resend the whole series or should
> we review/merge this rfc first (even though it is known to be
> incomplete in many disconnect cases that the follow up fixes).
> 
> thanks

I think a gradual merge is better.

> -- 
> Marc-André Lureau

Re: [Qemu-devel] [PATCH 00/10] RFCv3: vhost-user: simple reconnection support

[Yuanhan Liu]

On Sun, May 15, 2016 at 12:42:12PM +0300, Michael S. Tsirkin wrote:
> > FYI, I have a follow up series (~20 patches,
> > https://github.com/elmarco/qemu/tree/vhost-user-reconnect) doing
> > mostly cleanups and extra checks for disconnection at run time. In
> > particular, it should avoid some obvious crashers/asserts, and
> > prevents qemu from running as long the initial vhost_user_start()
> > didn't succeed (so initial flags are set). I would like to know how to
> > proceed with the follow-up: should I resend the whole series or should
> > we review/merge this rfc first (even though it is known to be
> > incomplete in many disconnect cases that the follow up fixes).
> > 
> > thanks
> 
> I think a gradual merge is better.

+1

May I ask what's the plan to merge this patch set? DPDK has some
dependency on this patch set.

	--yliu

Re: [Qemu-devel] [PATCH 00/10] RFCv3: vhost-user: simple reconnection support

[Marc-André Lureau]

Hi

On Mon, May 23, 2016 at 3:40 PM, Yuanhan Liu
<yuanhan.liu@linux.intel.com> wrote:
> On Sun, May 15, 2016 at 12:42:12PM +0300, Michael S. Tsirkin wrote:
>> > FYI, I have a follow up series (~20 patches,
>> > https://github.com/elmarco/qemu/tree/vhost-user-reconnect) doing
>> > mostly cleanups and extra checks for disconnection at run time. In
>> > particular, it should avoid some obvious crashers/asserts, and
>> > prevents qemu from running as long the initial vhost_user_start()
>> > didn't succeed (so initial flags are set). I would like to know how to
>> > proceed with the follow-up: should I resend the whole series or should
>> > we review/merge this rfc first (even though it is known to be
>> > incomplete in many disconnect cases that the follow up fixes).
>> >
>> > thanks
>>
>> I think a gradual merge is better.
>
> +1
>
> May I ask what's the plan to merge this patch set? DPDK has some
> dependency on this patch set.
>
>         --yliu

My understanding is we need someone to review and someone to pull this
series. Michael?

-- 
Marc-André Lureau

Re: [Qemu-devel] [PATCH 00/10] RFCv3: vhost-user: simple reconnection support

[Yuanhan Liu]

Hi Marc,

I was also thinking we should do it in this way first. That simplfies
things. So, feel free to add:

Tested-by: Yuanhan Liu <yuanhan.liu@linux.intel.com>
Reviewed-by: Yuanhan Liu <yuanhan.liu@linux.intel.com>

(well, I didn't review the test case carefully).

Thanks.

	--yliu

On Tue, May 10, 2016 at 06:03:50PM +0200, marcandre.lureau@redhat.com wrote:
> From: Marc-André Lureau <marcandre.lureau@redhat.com>
> 
> Hi,
> 
> In a previous series "RFCv2: vhost-user: shutdown and reconnection", I
> proposed to add a new slave request to handle graceful shutdown, for
> both qemu configuration, server or client, while keeping the guest
> running with link down status.
> 
> However, for the simple case where qemu is configured as server, and
> the backend processes packets in order and disconnects, it is possible
> for the backend to recover after reconnection by discarding the qemu
> SET_VRING_BASE value and resuming from the used->index instead. This
> simplifies the reconnection support in this particular situation (it
> would make sense to have the backend declare this behaviour with an
> extra flag)
> 
> The guest won't be notified of link status change and queues may not
> be processed in a timely manner, also qemu may assert if some
> vhost-user commands are happening while the backend is disconnected.
> So the reconnection must happen "quickly enough" here. In order to
> keep the series relatively small, these further problems will be
> addressed later.
> 
> These series demonstrates a simple reconnect support for vubr
> (configured as client and qemu as server), includes some nice to
> have fixes and a simple test.
> 
> Marc-André Lureau (8):
>   vubr: add client mode
>   vubr: workaround stale vring base
>   vhost-user: disconnect on start failure
>   vhost-net: do not crash if backend is not present
>   vhost-net: save & restore vhost-user acked features
>   vhost-net: save & restore vring enable state
>   tests: append i386 tests
>   test: start vhost-user reconnect test
> 
> Tetsuya Mukawa (2):
>   vhost-user: add ability to know vhost-user backend disconnection
>   qemu-char: add qemu_chr_disconnect to close a fd accepted by listen fd
> 
>  hw/net/vhost_net.c        |  39 ++++++++++++++-
>  include/net/net.h         |   1 +
>  include/net/vhost-user.h  |   1 +
>  include/net/vhost_net.h   |   3 ++
>  include/sysemu/char.h     |   7 +++
>  net/vhost-user.c          |  32 +++++++++++-
>  qemu-char.c               |   8 +++
>  tests/Makefile            |   2 +-
>  tests/vhost-user-bridge.c |  45 ++++++++++++-----
>  tests/vhost-user-test.c   | 123 +++++++++++++++++++++++++++++++++++++++-------
>  10 files changed, 228 insertions(+), 33 deletions(-)
> 
> -- 
> 2.7.4