[Qemu-devel] [PATCH] vhost-user: Add ability to know vhost-user backend disconnection

[Qemu-devel] [PATCH] vhost-user: Add ability to know vhost-user backend disconnection

[Tetsuya Mukawa]

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>
---
 net/vhost-user.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/net/vhost-user.c b/net/vhost-user.c
index 1d86a2b..55c05a5 100644
--- a/net/vhost-user.c
+++ b/net/vhost-user.c
@@ -19,6 +19,7 @@ typedef struct VhostUserState {
     NetClientState nc;
     CharDriverState *chr;
     VHostNetState *vhost_net;
+    int watch;
 } VhostUserState;
 
 typedef struct VhostUserChardevProps {
@@ -113,12 +114,23 @@ static void net_vhost_link_down(VhostUserState *s, bool link_down)
     }
 }
 
+static gboolean net_vhost_user_watch(GIOChannel *chan, GIOCondition cond,
+                                           void *opaque)
+{
+    VhostUserState *s = opaque;
+    uint8_t buf[1];
+
+    qemu_chr_fe_read_all(s->chr, buf, sizeof(buf));
+    return FALSE;
+}
+
 static void net_vhost_user_event(void *opaque, int event)
 {
     VhostUserState *s = opaque;
 
     switch (event) {
     case CHR_EVENT_OPENED:
+        s->watch = qemu_chr_fe_add_watch(s->chr, G_IO_HUP, net_vhost_user_watch, s);
         vhost_user_start(s);
         net_vhost_link_down(s, false);
         error_report("chardev \"%s\" went up", s->chr->label);
@@ -126,6 +138,8 @@ static void net_vhost_user_event(void *opaque, int event)
     case CHR_EVENT_CLOSED:
         net_vhost_link_down(s, true);
         vhost_user_stop(s);
+        g_source_remove(s->watch);
+        s->watch = 0;
         error_report("chardev \"%s\" went down", s->chr->label);
         break;
     }
-- 
1.9.1

Re: [Qemu-devel] [PATCH] vhost-user: Add ability to know vhost-user backend disconnection

[Nikolay Nikolaev]

On Tue, Apr 21, 2015 at 9:36 AM, Tetsuya Mukawa <mukawa@igel.co.jp> wrote:
> 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>
> ---
>  net/vhost-user.c | 14 ++++++++++++++
>  1 file changed, 14 insertions(+)
>
> diff --git a/net/vhost-user.c b/net/vhost-user.c
> index 1d86a2b..55c05a5 100644
> --- a/net/vhost-user.c
> +++ b/net/vhost-user.c
> @@ -19,6 +19,7 @@ typedef struct VhostUserState {
>      NetClientState nc;
>      CharDriverState *chr;
>      VHostNetState *vhost_net;
> +    int watch;
>  } VhostUserState;
>
>  typedef struct VhostUserChardevProps {
> @@ -113,12 +114,23 @@ static void net_vhost_link_down(VhostUserState *s, bool link_down)
>      }
>  }
>
> +static gboolean net_vhost_user_watch(GIOChannel *chan, GIOCondition cond,
> +                                           void *opaque)
> +{
> +    VhostUserState *s = opaque;
> +    uint8_t buf[1];
> +
> +    qemu_chr_fe_read_all(s->chr, buf, sizeof(buf));
So you read the date from the buffer and just discard it?
Are you going to miss messages this way?

Please clarify.

regards,
Nikolay Nikolaev

> +    return FALSE;
> +}
> +
>  static void net_vhost_user_event(void *opaque, int event)
>  {
>      VhostUserState *s = opaque;
>
>      switch (event) {
>      case CHR_EVENT_OPENED:
> +        s->watch = qemu_chr_fe_add_watch(s->chr, G_IO_HUP, net_vhost_user_watch, s);
>          vhost_user_start(s);
>          net_vhost_link_down(s, false);
>          error_report("chardev \"%s\" went up", s->chr->label);
> @@ -126,6 +138,8 @@ static void net_vhost_user_event(void *opaque, int event)
>      case CHR_EVENT_CLOSED:
>          net_vhost_link_down(s, true);
>          vhost_user_stop(s);
> +        g_source_remove(s->watch);
> +        s->watch = 0;
>          error_report("chardev \"%s\" went down", s->chr->label);
>          break;
>      }
> --
> 1.9.1
>
>

Re: [Qemu-devel] [PATCH] vhost-user: Add ability to know vhost-user backend disconnection

[Tetsuya Mukawa]

On 2015/04/22 5:19, Nikolay Nikolaev wrote:
> On Tue, Apr 21, 2015 at 9:36 AM, Tetsuya Mukawa <mukawa@igel.co.jp> wrote:
>> 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>
>> ---
>>  net/vhost-user.c | 14 ++++++++++++++
>>  1 file changed, 14 insertions(+)
>>
>> diff --git a/net/vhost-user.c b/net/vhost-user.c
>> index 1d86a2b..55c05a5 100644
>> --- a/net/vhost-user.c
>> +++ b/net/vhost-user.c
>> @@ -19,6 +19,7 @@ typedef struct VhostUserState {
>>      NetClientState nc;
>>      CharDriverState *chr;
>>      VHostNetState *vhost_net;
>> +    int watch;
>>  } VhostUserState;
>>
>>  typedef struct VhostUserChardevProps {
>> @@ -113,12 +114,23 @@ static void net_vhost_link_down(VhostUserState *s, bool link_down)
>>      }
>>  }
>>
>> +static gboolean net_vhost_user_watch(GIOChannel *chan, GIOCondition cond,
>> +                                           void *opaque)
>> +{
>> +    VhostUserState *s = opaque;
>> +    uint8_t buf[1];
>> +
>> +    qemu_chr_fe_read_all(s->chr, buf, sizeof(buf));
> So you read the date from the buffer and just discard it?
> Are you going to miss messages this way?
>
> Please clarify.

Hi Nikolay,

Thanks for comment.
Yes, some messages might be lost, but it will be only happened after
unix domain socket is closed by vhost-user backend.
So I guess there is no side effect.
Anyway, I just want to know vhost-user disconnection, so other ways are
also nice.
Do you have any suggestions about how to implement?

Regards,
Tetsuya

> regards,
> Nikolay Nikolaev
>
>> +    return FALSE;
>> +}
>> +
>>  static void net_vhost_user_event(void *opaque, int event)
>>  {
>>      VhostUserState *s = opaque;
>>
>>      switch (event) {
>>      case CHR_EVENT_OPENED:
>> +        s->watch = qemu_chr_fe_add_watch(s->chr, G_IO_HUP, net_vhost_user_watch, s);
>>          vhost_user_start(s);
>>          net_vhost_link_down(s, false);
>>          error_report("chardev \"%s\" went up", s->chr->label);
>> @@ -126,6 +138,8 @@ static void net_vhost_user_event(void *opaque, int event)
>>      case CHR_EVENT_CLOSED:
>>          net_vhost_link_down(s, true);
>>          vhost_user_stop(s);
>> +        g_source_remove(s->watch);
>> +        s->watch = 0;
>>          error_report("chardev \"%s\" went down", s->chr->label);
>>          break;
>>      }
>> --
>> 1.9.1
>>
>>