[Qemu-devel] [PATCH 1/8] RFC: chardev frontend open handling cleanup

[Qemu-devel] [PATCH 1/8] RFC: chardev frontend open handling cleanup

[Hans de Goede]

This patch-series is the result of the
"[PATCH 1/2] char: add qemu_chr_be_is_fe_connected" discussion thread.

This patch series (tries to) make(s) the frontend open concept both more
explicit and generic, and significantly cleans up the surrounding code.

Regards,

Hans

[Qemu-devel] [PATCH 1/8] qemu-char: Rename opened to be_open

[Hans de Goede]

Rename the opened variable to be_open to reflect that it contains the
opened state of the backend.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
---
 hw/usb/dev-serial.c | 2 +-
 hw/usb/redirect.c   | 2 +-
 include/char/char.h | 2 +-
 qemu-char.c         | 6 +++---
 spice-qemu-char.c   | 4 ++--
 5 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/hw/usb/dev-serial.c b/hw/usb/dev-serial.c
index 47ac8c9..7c314dc 100644
--- a/hw/usb/dev-serial.c
+++ b/hw/usb/dev-serial.c
@@ -495,7 +495,7 @@ static int usb_serial_initfn(USBDevice *dev)
                           usb_serial_event, s);
     usb_serial_handle_reset(dev);
 
-    if (s->cs->opened && !dev->attached) {
+    if (s->cs->be_open && !dev->attached) {
         usb_device_attach(dev);
     }
     return 0;
diff --git a/hw/usb/redirect.c b/hw/usb/redirect.c
index e0df74b..4d565ba 100644
--- a/hw/usb/redirect.c
+++ b/hw/usb/redirect.c
@@ -272,7 +272,7 @@ static int usbredir_write(void *priv, uint8_t *data, int count)
     USBRedirDevice *dev = priv;
     int r;
 
-    if (!dev->cs->opened) {
+    if (!dev->cs->be_open) {
         return 0;
     }
 
diff --git a/include/char/char.h b/include/char/char.h
index 0326b2a..d801f92 100644
--- a/include/char/char.h
+++ b/include/char/char.h
@@ -74,7 +74,7 @@ struct CharDriverState {
     int idle_tag;
     char *label;
     char *filename;
-    int opened;
+    int be_open;
     int avail_connections;
     QemuOpts *opts;
     QTAILQ_ENTRY(CharDriverState) next;
diff --git a/qemu-char.c b/qemu-char.c
index 4e011df..32a05af 100644
--- a/qemu-char.c
+++ b/qemu-char.c
@@ -108,10 +108,10 @@ void qemu_chr_be_event(CharDriverState *s, int event)
     /* Keep track if the char device is open */
     switch (event) {
         case CHR_EVENT_OPENED:
-            s->opened = 1;
+            s->be_open = 1;
             break;
         case CHR_EVENT_CLOSED:
-            s->opened = 0;
+            s->be_open = 0;
             break;
     }
 
@@ -207,7 +207,7 @@ void qemu_chr_add_handlers(CharDriverState *s,
 
     /* We're connecting to an already opened device, so let's make sure we
        also get the open event */
-    if (s->opened) {
+    if (s->be_open) {
         qemu_chr_generic_open(s);
     }
 }
diff --git a/spice-qemu-char.c b/spice-qemu-char.c
index 607abb6..613cc64 100644
--- a/spice-qemu-char.c
+++ b/spice-qemu-char.c
@@ -91,8 +91,8 @@ static void vmc_state(SpiceCharDeviceInstance *sin, int connected)
 {
     SpiceCharDriver *scd = container_of(sin, SpiceCharDriver, sin);
 
-    if ((scd->chr->opened && connected) ||
-        (!scd->chr->opened && !connected)) {
+    if ((scd->chr->be_open && connected) ||
+        (!scd->chr->be_open && !connected)) {
         return;
     }
 
-- 
1.8.1.4

[Qemu-devel] [PATCH 2/8] qemu-char: Rename qemu_chr_generic_open to qemu_chr_be_generic_open

[Hans de Goede]

To better reflect that it is for handling a backend being opened.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
---
 backends/baum.c     |  2 +-
 include/char/char.h |  2 +-
 qemu-char.c         | 24 ++++++++++++------------
 ui/console.c        |  2 +-
 ui/gtk.c            |  2 +-
 5 files changed, 16 insertions(+), 16 deletions(-)

diff --git a/backends/baum.c b/backends/baum.c
index d7d658c..ea9ffe8 100644
--- a/backends/baum.c
+++ b/backends/baum.c
@@ -611,7 +611,7 @@ CharDriverState *chr_baum_init(void)
 
     qemu_set_fd_handler(baum->brlapi_fd, baum_chr_read, NULL, baum);
 
-    qemu_chr_generic_open(chr);
+    qemu_chr_be_generic_open(chr);
 
     return chr;
 
diff --git a/include/char/char.h b/include/char/char.h
index d801f92..dd8f39a 100644
--- a/include/char/char.h
+++ b/include/char/char.h
@@ -235,7 +235,7 @@ void qemu_chr_add_handlers(CharDriverState *s,
                            IOEventHandler *fd_event,
                            void *opaque);
 
-void qemu_chr_generic_open(CharDriverState *s);
+void qemu_chr_be_generic_open(CharDriverState *s);
 void qemu_chr_accept_input(CharDriverState *s);
 int qemu_chr_add_client(CharDriverState *s, int fd);
 void qemu_chr_info_print(Monitor *mon, const QObject *ret_data);
diff --git a/qemu-char.c b/qemu-char.c
index 32a05af..55795d7 100644
--- a/qemu-char.c
+++ b/qemu-char.c
@@ -120,7 +120,7 @@ void qemu_chr_be_event(CharDriverState *s, int event)
     s->chr_event(s->handler_opaque, event);
 }
 
-static gboolean qemu_chr_generic_open_bh(gpointer opaque)
+static gboolean qemu_chr_be_generic_open_bh(gpointer opaque)
 {
     CharDriverState *s = opaque;
     qemu_chr_be_event(s, CHR_EVENT_OPENED);
@@ -128,10 +128,10 @@ static gboolean qemu_chr_generic_open_bh(gpointer opaque)
     return FALSE;
 }
 
-void qemu_chr_generic_open(CharDriverState *s)
+void qemu_chr_be_generic_open(CharDriverState *s)
 {
     if (s->idle_tag == 0) {
-        s->idle_tag = g_idle_add(qemu_chr_generic_open_bh, s);
+        s->idle_tag = g_idle_add(qemu_chr_be_generic_open_bh, s);
     }
 }
 
@@ -208,7 +208,7 @@ void qemu_chr_add_handlers(CharDriverState *s,
     /* We're connecting to an already opened device, so let's make sure we
        also get the open event */
     if (s->be_open) {
-        qemu_chr_generic_open(s);
+        qemu_chr_be_generic_open(s);
     }
 }
 
@@ -482,7 +482,7 @@ static CharDriverState *qemu_chr_open_mux(CharDriverState *drv)
     chr->chr_guest_close = NULL;
 
     /* Muxes are always open on creation */
-    qemu_chr_generic_open(chr);
+    qemu_chr_be_generic_open(chr);
 
     return chr;
 }
@@ -836,7 +836,7 @@ static CharDriverState *qemu_chr_open_fd(int fd_in, int fd_out)
     chr->chr_update_read_handler = fd_chr_update_read_handler;
     chr->chr_close = fd_chr_close;
 
-    qemu_chr_generic_open(chr);
+    qemu_chr_be_generic_open(chr);
 
     return chr;
 }
@@ -1133,7 +1133,7 @@ static void pty_chr_state(CharDriverState *chr, int connected)
         pty_chr_rearm_timer(chr, 1000);
     } else {
         if (!s->connected)
-            qemu_chr_generic_open(chr);
+            qemu_chr_be_generic_open(chr);
         s->connected = 1;
     }
 }
@@ -1549,7 +1549,7 @@ static CharDriverState *qemu_chr_open_pp_fd(int fd)
     chr->chr_close = pp_close;
     chr->opaque = drv;
 
-    qemu_chr_generic_open(chr);
+    qemu_chr_be_generic_open(chr);
 
     return chr;
 }
@@ -1834,7 +1834,7 @@ static CharDriverState *qemu_chr_open_win_path(const char *filename)
         g_free(chr);
         return NULL;
     }
-    qemu_chr_generic_open(chr);
+    qemu_chr_be_generic_open(chr);
     return chr;
 }
 
@@ -1934,7 +1934,7 @@ static CharDriverState *qemu_chr_open_pipe(ChardevHostdev *opts)
         g_free(chr);
         return NULL;
     }
-    qemu_chr_generic_open(chr);
+    qemu_chr_be_generic_open(chr);
     return chr;
 }
 
@@ -1948,7 +1948,7 @@ static CharDriverState *qemu_chr_open_win_file(HANDLE fd_out)
     s->hcom = fd_out;
     chr->opaque = s;
     chr->chr_write = win_chr_write;
-    qemu_chr_generic_open(chr);
+    qemu_chr_be_generic_open(chr);
     return chr;
 }
 
@@ -2513,7 +2513,7 @@ static void tcp_chr_connect(void *opaque)
     if (s->chan) {
         s->tag = io_add_watch_poll(s->chan, tcp_chr_read_poll, tcp_chr_read, chr);
     }
-    qemu_chr_generic_open(chr);
+    qemu_chr_be_generic_open(chr);
 }
 
 #define IACSET(x,a,b,c) x[0] = a; x[1] = b; x[2] = c;
diff --git a/ui/console.c b/ui/console.c
index eb7a2bc..e84ba8b 100644
--- a/ui/console.c
+++ b/ui/console.c
@@ -1600,7 +1600,7 @@ static void text_console_do_init(CharDriverState *chr, DisplayState *ds)
         s->t_attrib = s->t_attrib_default;
     }
 
-    qemu_chr_generic_open(chr);
+    qemu_chr_be_generic_open(chr);
     if (chr->init)
         chr->init(chr);
 }
diff --git a/ui/gtk.c b/ui/gtk.c
index 305940d..903b4d4 100644
--- a/ui/gtk.c
+++ b/ui/gtk.c
@@ -1116,7 +1116,7 @@ static GSList *gd_vc_init(GtkDisplayState *s, VirtualConsole *vc, int index, GSL
 
     gtk_menu_shell_append(GTK_MENU_SHELL(s->view_menu), vc->menu_item);
 
-    qemu_chr_generic_open(vc->chr);
+    qemu_chr_be_generic_open(vc->chr);
     if (vc->chr->init) {
         vc->chr->init(vc->chr);
     }
-- 
1.8.1.4

[Qemu-devel] [PATCH 3/8] qemu-char: Add fe_open tracking

[Hans de Goede]

Add tracking of the fe_open state to struct CharDriverState.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
---
 include/char/char.h | 1 +
 qemu-char.c         | 2 ++
 2 files changed, 3 insertions(+)

diff --git a/include/char/char.h b/include/char/char.h
index dd8f39a..3174575 100644
--- a/include/char/char.h
+++ b/include/char/char.h
@@ -75,6 +75,7 @@ struct CharDriverState {
     char *label;
     char *filename;
     int be_open;
+    int fe_open;
     int avail_connections;
     QemuOpts *opts;
     QTAILQ_ENTRY(CharDriverState) next;
diff --git a/qemu-char.c b/qemu-char.c
index 55795d7..554d72f 100644
--- a/qemu-char.c
+++ b/qemu-char.c
@@ -3385,6 +3385,7 @@ void qemu_chr_fe_set_echo(struct CharDriverState *chr, bool echo)
 
 void qemu_chr_fe_open(struct CharDriverState *chr)
 {
+    chr->fe_open = 1;
     if (chr->chr_guest_open) {
         chr->chr_guest_open(chr);
     }
@@ -3392,6 +3393,7 @@ void qemu_chr_fe_open(struct CharDriverState *chr)
 
 void qemu_chr_fe_close(struct CharDriverState *chr)
 {
+    chr->fe_open = 0;
     if (chr->chr_guest_close) {
         chr->chr_guest_close(chr);
     }
-- 
1.8.1.4

Re: [Qemu-devel] [PATCH 3/8] qemu-char: Add fe_open tracking

[Anthony Liguori]

Hans de Goede <hdegoede@redhat.com> writes:

> Add tracking of the fe_open state to struct CharDriverState.
>
> Signed-off-by: Hans de Goede <hdegoede@redhat.com>
> ---
>  include/char/char.h | 1 +
>  qemu-char.c         | 2 ++
>  2 files changed, 3 insertions(+)
>
> diff --git a/include/char/char.h b/include/char/char.h
> index dd8f39a..3174575 100644
> --- a/include/char/char.h
> +++ b/include/char/char.h
> @@ -75,6 +75,7 @@ struct CharDriverState {
>      char *label;
>      char *filename;
>      int be_open;
> +    int fe_open;
>      int avail_connections;
>      QemuOpts *opts;
>      QTAILQ_ENTRY(CharDriverState) next;
> diff --git a/qemu-char.c b/qemu-char.c
> index 55795d7..554d72f 100644
> --- a/qemu-char.c
> +++ b/qemu-char.c
> @@ -3385,6 +3385,7 @@ void qemu_chr_fe_set_echo(struct CharDriverState *chr, bool echo)
>  
>  void qemu_chr_fe_open(struct CharDriverState *chr)
>  {
> +    chr->fe_open = 1;
>      if (chr->chr_guest_open) {
>          chr->chr_guest_open(chr);
>      }
> @@ -3392,6 +3393,7 @@ void qemu_chr_fe_open(struct CharDriverState *chr)
>  
>  void qemu_chr_fe_close(struct CharDriverState *chr)
>  {
> +    chr->fe_open = 0;

Even though this gets rewritten later on, you should avoid calling the
callback when open is called when fe_open=1.  Something like

if (!chr->fe_open) {
    return;
}

Then later when this becomes set_fe_open() the backend doesn't need to
deal with double open/close.

Regards,

Anthony Liguori

>      if (chr->chr_guest_close) {
>          chr->chr_guest_close(chr);
>      }
> -- 
> 1.8.1.4

Re: [Qemu-devel] [PATCH 3/8] qemu-char: Add fe_open tracking

[Hans de Goede]

Hi,

On 03/25/2013 01:45 PM, Anthony Liguori wrote:
> Hans de Goede <hdegoede@redhat.com> writes:
>
>> Add tracking of the fe_open state to struct CharDriverState.
>>
>> Signed-off-by: Hans de Goede <hdegoede@redhat.com>
>> ---
>>   include/char/char.h | 1 +
>>   qemu-char.c         | 2 ++
>>   2 files changed, 3 insertions(+)
>>
>> diff --git a/include/char/char.h b/include/char/char.h
>> index dd8f39a..3174575 100644
>> --- a/include/char/char.h
>> +++ b/include/char/char.h
>> @@ -75,6 +75,7 @@ struct CharDriverState {
>>       char *label;
>>       char *filename;
>>       int be_open;
>> +    int fe_open;
>>       int avail_connections;
>>       QemuOpts *opts;
>>       QTAILQ_ENTRY(CharDriverState) next;
>> diff --git a/qemu-char.c b/qemu-char.c
>> index 55795d7..554d72f 100644
>> --- a/qemu-char.c
>> +++ b/qemu-char.c
>> @@ -3385,6 +3385,7 @@ void qemu_chr_fe_set_echo(struct CharDriverState *chr, bool echo)
>>
>>   void qemu_chr_fe_open(struct CharDriverState *chr)
>>   {
>> +    chr->fe_open = 1;
>>       if (chr->chr_guest_open) {
>>           chr->chr_guest_open(chr);
>>       }
>> @@ -3392,6 +3393,7 @@ void qemu_chr_fe_open(struct CharDriverState *chr)
>>
>>   void qemu_chr_fe_close(struct CharDriverState *chr)
>>   {
>> +    chr->fe_open = 0;
>
> Even though this gets rewritten later on, you should avoid calling the
> callback when open is called when fe_open=1.  Something like
>
> if (!chr->fe_open) {
>      return;
> }
>
> Then later when this becomes set_fe_open() the backend doesn't need to
> deal with double open/close.

Ok, will fix in the next iteration of this patchset.

Regards,

Hans

[Qemu-devel] [PATCH 4/8] qemu-char: Automatically do fe_open / fe_close on qemu_chr_add_handlers

[Hans de Goede]

Most frontends can't really determine if the guest actually has the frontend
side open. So lets automatically generate fe_open / fe_close as soon as a
frontend becomes ready (as signalled by calling qemu_chr_add_handlers) /
becomes non ready (as signalled by setting all handlers to NULL).

And allow frontends which can actually determine if the guest is listening to
opt-out of this.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
---
 hw/usb/redirect.c   |  2 --
 hw/virtio-console.c |  1 +
 include/char/char.h |  1 +
 qemu-char.c         | 13 +++++++++++++
 4 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/hw/usb/redirect.c b/hw/usb/redirect.c
index 4d565ba..0ddb081 100644
--- a/hw/usb/redirect.c
+++ b/hw/usb/redirect.c
@@ -1310,7 +1310,6 @@ static int usbredir_initfn(USBDevice *udev)
     dev->compatible_speedmask = USB_SPEED_MASK_FULL | USB_SPEED_MASK_HIGH;
 
     /* Let the backend know we are ready */
-    qemu_chr_fe_open(dev->cs);
     qemu_chr_add_handlers(dev->cs, usbredir_chardev_can_read,
                           usbredir_chardev_read, usbredir_chardev_event, dev);
 
@@ -1334,7 +1333,6 @@ static void usbredir_handle_destroy(USBDevice *udev)
 {
     USBRedirDevice *dev = DO_UPCAST(USBRedirDevice, dev, udev);
 
-    qemu_chr_fe_close(dev->cs);
     qemu_chr_delete(dev->cs);
     /* Note must be done after qemu_chr_close, as that causes a close event */
     qemu_bh_delete(dev->chardev_close_bh);
diff --git a/hw/virtio-console.c b/hw/virtio-console.c
index 8ef76e2..209ea38 100644
--- a/hw/virtio-console.c
+++ b/hw/virtio-console.c
@@ -140,6 +140,7 @@ static int virtconsole_initfn(VirtIOSerialPort *port)
     }
 
     if (vcon->chr) {
+        vcon->chr->explicit_fe_open = 1;
         qemu_chr_add_handlers(vcon->chr, chr_can_read, chr_read, chr_event,
                               vcon);
     }
diff --git a/include/char/char.h b/include/char/char.h
index 3174575..27ebbc3 100644
--- a/include/char/char.h
+++ b/include/char/char.h
@@ -76,6 +76,7 @@ struct CharDriverState {
     char *filename;
     int be_open;
     int fe_open;
+    int explicit_fe_open;
     int avail_connections;
     QemuOpts *opts;
     QTAILQ_ENTRY(CharDriverState) next;
diff --git a/qemu-char.c b/qemu-char.c
index 554d72f..7c57971 100644
--- a/qemu-char.c
+++ b/qemu-char.c
@@ -194,9 +194,14 @@ void qemu_chr_add_handlers(CharDriverState *s,
                            IOEventHandler *fd_event,
                            void *opaque)
 {
+    int fe_open;
+
     if (!opaque && !fd_can_read && !fd_read && !fd_event) {
         /* chr driver being released. */
+        fe_open = 0;
         ++s->avail_connections;
+    } else {
+        fe_open = 1;
     }
     s->chr_can_read = fd_can_read;
     s->chr_read = fd_read;
@@ -205,6 +210,14 @@ void qemu_chr_add_handlers(CharDriverState *s,
     if (s->chr_update_read_handler)
         s->chr_update_read_handler(s);
 
+    if (!s->explicit_fe_open) {
+        if (fe_open) {
+            qemu_chr_fe_open(s);
+        } else {
+            qemu_chr_fe_close(s);
+        }
+    }
+
     /* We're connecting to an already opened device, so let's make sure we
        also get the open event */
     if (s->be_open) {
-- 
1.8.1.4

Re: [Qemu-devel] [PATCH 4/8] qemu-char: Automatically do fe_open / fe_close on qemu_chr_add_handlers

[Anthony Liguori]

Hans de Goede <hdegoede@redhat.com> writes:

> Most frontends can't really determine if the guest actually has the frontend
> side open. So lets automatically generate fe_open / fe_close as soon as a
> frontend becomes ready (as signalled by calling qemu_chr_add_handlers) /
> becomes non ready (as signalled by setting all handlers to NULL).
>
> And allow frontends which can actually determine if the guest is listening to
> opt-out of this.

Could we change virtio-serial to delay calling add_handlers so that we
could not introduce this variable?

Regards,

Anthony Liguori

>
> Signed-off-by: Hans de Goede <hdegoede@redhat.com>
> ---
>  hw/usb/redirect.c   |  2 --
>  hw/virtio-console.c |  1 +
>  include/char/char.h |  1 +
>  qemu-char.c         | 13 +++++++++++++
>  4 files changed, 15 insertions(+), 2 deletions(-)
>
> diff --git a/hw/usb/redirect.c b/hw/usb/redirect.c
> index 4d565ba..0ddb081 100644
> --- a/hw/usb/redirect.c
> +++ b/hw/usb/redirect.c
> @@ -1310,7 +1310,6 @@ static int usbredir_initfn(USBDevice *udev)
>      dev->compatible_speedmask = USB_SPEED_MASK_FULL | USB_SPEED_MASK_HIGH;
>  
>      /* Let the backend know we are ready */
> -    qemu_chr_fe_open(dev->cs);
>      qemu_chr_add_handlers(dev->cs, usbredir_chardev_can_read,
>                            usbredir_chardev_read, usbredir_chardev_event, dev);
>  
> @@ -1334,7 +1333,6 @@ static void usbredir_handle_destroy(USBDevice *udev)
>  {
>      USBRedirDevice *dev = DO_UPCAST(USBRedirDevice, dev, udev);
>  
> -    qemu_chr_fe_close(dev->cs);
>      qemu_chr_delete(dev->cs);
>      /* Note must be done after qemu_chr_close, as that causes a close event */
>      qemu_bh_delete(dev->chardev_close_bh);
> diff --git a/hw/virtio-console.c b/hw/virtio-console.c
> index 8ef76e2..209ea38 100644
> --- a/hw/virtio-console.c
> +++ b/hw/virtio-console.c
> @@ -140,6 +140,7 @@ static int virtconsole_initfn(VirtIOSerialPort *port)
>      }
>  
>      if (vcon->chr) {
> +        vcon->chr->explicit_fe_open = 1;
>          qemu_chr_add_handlers(vcon->chr, chr_can_read, chr_read, chr_event,
>                                vcon);
>      }
> diff --git a/include/char/char.h b/include/char/char.h
> index 3174575..27ebbc3 100644
> --- a/include/char/char.h
> +++ b/include/char/char.h
> @@ -76,6 +76,7 @@ struct CharDriverState {
>      char *filename;
>      int be_open;
>      int fe_open;
> +    int explicit_fe_open;
>      int avail_connections;
>      QemuOpts *opts;
>      QTAILQ_ENTRY(CharDriverState) next;
> diff --git a/qemu-char.c b/qemu-char.c
> index 554d72f..7c57971 100644
> --- a/qemu-char.c
> +++ b/qemu-char.c
> @@ -194,9 +194,14 @@ void qemu_chr_add_handlers(CharDriverState *s,
>                             IOEventHandler *fd_event,
>                             void *opaque)
>  {
> +    int fe_open;
> +
>      if (!opaque && !fd_can_read && !fd_read && !fd_event) {
>          /* chr driver being released. */
> +        fe_open = 0;
>          ++s->avail_connections;
> +    } else {
> +        fe_open = 1;
>      }
>      s->chr_can_read = fd_can_read;
>      s->chr_read = fd_read;
> @@ -205,6 +210,14 @@ void qemu_chr_add_handlers(CharDriverState *s,
>      if (s->chr_update_read_handler)
>          s->chr_update_read_handler(s);
>  
> +    if (!s->explicit_fe_open) {
> +        if (fe_open) {
> +            qemu_chr_fe_open(s);
> +        } else {
> +            qemu_chr_fe_close(s);
> +        }
> +    }
> +
>      /* We're connecting to an already opened device, so let's make sure we
>         also get the open event */
>      if (s->be_open) {
> -- 
> 1.8.1.4

Re: [Qemu-devel] [PATCH 4/8] qemu-char: Automatically do fe_open / fe_close on qemu_chr_add_handlers

[Hans de Goede]

Hi,

On 03/25/2013 01:46 PM, Anthony Liguori wrote:
> Hans de Goede <hdegoede@redhat.com> writes:
>
>> Most frontends can't really determine if the guest actually has the frontend
>> side open. So lets automatically generate fe_open / fe_close as soon as a
>> frontend becomes ready (as signalled by calling qemu_chr_add_handlers) /
>> becomes non ready (as signalled by setting all handlers to NULL).
>>
>> And allow frontends which can actually determine if the guest is listening to
>> opt-out of this.
>
> Could we change virtio-serial to delay calling add_handlers so that we
> could not introduce this variable?

Hmm, I was trying to avoid opening that can of worms. I've taken a quick look
and there are 2 issues with doing this:
1) It will wreck havoc with CharDriverState.avail_connections, since that
    gets increased on a qemu_chr_add_handlers( NULL ), while it is decreased
    only once in hw/qdev-properties-system.c

This can be fixed by moving the avail_connections++ to
hw/qdev-properties-system.c: release_chr, which seems the sensible thing to
do wrt nicely balancing out these calls anyways.

2) It will cause the virtio-console front-end to miss various events, such
as backend open/close events.

A backend open event will get "replayed" when qemu_chr_add_handlers( stuff )
is called, causing a potential double open from the virtio-console pov
(one before it called qemu_chr_add_handlers( NULL ), and one on the next
add_handlers call). And a close or any other events happening while the
frontend side is closed will be missed.

I'll gladly add a patch fixing 1). to the next revision of this patchset,
but given 2) I would prefer to stick with the explicit_fe_open flag and just
register the handlers once.

Regards,

Hans

Re: [Qemu-devel] [PATCH 4/8] qemu-char: Automatically do fe_open / fe_close on qemu_chr_add_handlers

[Anthony Liguori]

Hans de Goede <hdegoede@redhat.com> writes:

> Hi,
>
> On 03/25/2013 01:46 PM, Anthony Liguori wrote:
>> Hans de Goede <hdegoede@redhat.com> writes:
>>
>>> Most frontends can't really determine if the guest actually has the frontend
>>> side open. So lets automatically generate fe_open / fe_close as soon as a
>>> frontend becomes ready (as signalled by calling qemu_chr_add_handlers) /
>>> becomes non ready (as signalled by setting all handlers to NULL).
>>>
>>> And allow frontends which can actually determine if the guest is listening to
>>> opt-out of this.
>>
>> Could we change virtio-serial to delay calling add_handlers so that we
>> could not introduce this variable?
>
> Hmm, I was trying to avoid opening that can of worms. I've taken a quick look
> and there are 2 issues with doing this:
> 1) It will wreck havoc with CharDriverState.avail_connections, since that
>     gets increased on a qemu_chr_add_handlers( NULL ), while it is decreased
>     only once in hw/qdev-properties-system.c
>
> This can be fixed by moving the avail_connections++ to
> hw/qdev-properties-system.c: release_chr, which seems the sensible thing to
> do wrt nicely balancing out these calls anyways.
>
> 2) It will cause the virtio-console front-end to miss various events, such
> as backend open/close events.
>
> A backend open event will get "replayed" when qemu_chr_add_handlers( stuff )
> is called, causing a potential double open from the virtio-console pov
> (one before it called qemu_chr_add_handlers( NULL ), and one on the next
> add_handlers call). And a close or any other events happening while the
> frontend side is closed will be missed.
>
> I'll gladly add a patch fixing 1). to the next revision of this patchset,
> but given 2) I would prefer to stick with the explicit_fe_open flag and just
> register the handlers once.

Okay, seems reasonable.

REgards,

Anthony Liguori

>
> Regards,
>
> Hans

[Qemu-devel] [PATCH 5/8] qemu-char: Cleanup: consolidate fe_open/fe_close into fe_set_open

[Hans de Goede]

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
---
 hw/virtio-console.c |  4 ++--
 include/char/char.h | 17 ++++-------------
 qemu-char.c         | 19 +++++--------------
 3 files changed, 11 insertions(+), 29 deletions(-)

diff --git a/hw/virtio-console.c b/hw/virtio-console.c
index 209ea38..c0d41c5 100644
--- a/hw/virtio-console.c
+++ b/hw/virtio-console.c
@@ -79,7 +79,7 @@ static void guest_open(VirtIOSerialPort *port)
     if (!vcon->chr) {
         return;
     }
-    qemu_chr_fe_open(vcon->chr);
+    qemu_chr_fe_set_open(vcon->chr, 1);
 }
 
 /* Callback function that's called when the guest closes the port */
@@ -90,7 +90,7 @@ static void guest_close(VirtIOSerialPort *port)
     if (!vcon->chr) {
         return;
     }
-    qemu_chr_fe_close(vcon->chr);
+    qemu_chr_fe_set_open(vcon->chr, 0);
 }
 
 /* Readiness of the guest to accept data on a port */
diff --git a/include/char/char.h b/include/char/char.h
index 27ebbc3..3c8dd28 100644
--- a/include/char/char.h
+++ b/include/char/char.h
@@ -129,21 +129,12 @@ void qemu_chr_delete(CharDriverState *chr);
 void qemu_chr_fe_set_echo(struct CharDriverState *chr, bool echo);
 
 /**
- * @qemu_chr_fe_open:
+ * @qemu_chr_fe_set_open:
  *
- * Open a character backend.  This function call is an indication that the
- * front end is ready to begin doing I/O.
+ * Set character frontend open status.  This is an indication that the
+ * front end is ready (or not) to begin doing I/O.
  */
-void qemu_chr_fe_open(struct CharDriverState *chr);
-
-/**
- * @qemu_chr_fe_close:
- *
- * Close a character backend.  This function call indicates that the front end
- * no longer is able to process I/O.  To process I/O again, the front end will
- * call @qemu_chr_fe_open.
- */
-void qemu_chr_fe_close(struct CharDriverState *chr);
+void qemu_chr_fe_set_open(struct CharDriverState *chr, int fe_open);
 
 /**
  * @qemu_chr_fe_printf:
diff --git a/qemu-char.c b/qemu-char.c
index 7c57971..713c154 100644
--- a/qemu-char.c
+++ b/qemu-char.c
@@ -211,11 +211,7 @@ void qemu_chr_add_handlers(CharDriverState *s,
         s->chr_update_read_handler(s);
 
     if (!s->explicit_fe_open) {
-        if (fe_open) {
-            qemu_chr_fe_open(s);
-        } else {
-            qemu_chr_fe_close(s);
-        }
+        qemu_chr_fe_set_open(s, fe_open);
     }
 
     /* We're connecting to an already opened device, so let's make sure we
@@ -3396,18 +3392,13 @@ void qemu_chr_fe_set_echo(struct CharDriverState *chr, bool echo)
     }
 }
 
-void qemu_chr_fe_open(struct CharDriverState *chr)
+void qemu_chr_fe_set_open(struct CharDriverState *chr, int fe_open)
 {
-    chr->fe_open = 1;
-    if (chr->chr_guest_open) {
+    chr->fe_open = fe_open;
+    if (fe_open && chr->chr_guest_open) {
         chr->chr_guest_open(chr);
     }
-}
-
-void qemu_chr_fe_close(struct CharDriverState *chr)
-{
-    chr->fe_open = 0;
-    if (chr->chr_guest_close) {
+    if (!fe_open && chr->chr_guest_close) {
         chr->chr_guest_close(chr);
     }
 }
-- 
1.8.1.4

[Qemu-devel] [PATCH 6/8] qemu-char: Consolidate guest_close/guest_open into a set_fe_open callback

[Hans de Goede]

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
---
 include/char/char.h |  3 +--
 qemu-char.c         | 10 +++-------
 spice-qemu-char.c   | 17 +++++++----------
 3 files changed, 11 insertions(+), 19 deletions(-)

diff --git a/include/char/char.h b/include/char/char.h
index 3c8dd28..1457e80 100644
--- a/include/char/char.h
+++ b/include/char/char.h
@@ -68,8 +68,7 @@ struct CharDriverState {
     void (*chr_close)(struct CharDriverState *chr);
     void (*chr_accept_input)(struct CharDriverState *chr);
     void (*chr_set_echo)(struct CharDriverState *chr, bool echo);
-    void (*chr_guest_open)(struct CharDriverState *chr);
-    void (*chr_guest_close)(struct CharDriverState *chr);
+    void (*chr_set_fe_open)(struct CharDriverState *chr, int fe_open);
     void *opaque;
     int idle_tag;
     char *label;
diff --git a/qemu-char.c b/qemu-char.c
index 713c154..5be2ae7 100644
--- a/qemu-char.c
+++ b/qemu-char.c
@@ -487,8 +487,7 @@ static CharDriverState *qemu_chr_open_mux(CharDriverState *drv)
     chr->chr_update_read_handler = mux_chr_update_read_handler;
     chr->chr_accept_input = mux_chr_accept_input;
     /* Frontend guest-open / -close notification is not support with muxes */
-    chr->chr_guest_open = NULL;
-    chr->chr_guest_close = NULL;
+    chr->chr_set_fe_open = NULL;
 
     /* Muxes are always open on creation */
     qemu_chr_be_generic_open(chr);
@@ -3395,11 +3394,8 @@ void qemu_chr_fe_set_echo(struct CharDriverState *chr, bool echo)
 void qemu_chr_fe_set_open(struct CharDriverState *chr, int fe_open)
 {
     chr->fe_open = fe_open;
-    if (fe_open && chr->chr_guest_open) {
-        chr->chr_guest_open(chr);
-    }
-    if (!fe_open && chr->chr_guest_close) {
-        chr->chr_guest_close(chr);
+    if (chr->chr_set_fe_open) {
+        chr->chr_set_fe_open(chr, fe_open);
     }
 }
 
diff --git a/spice-qemu-char.c b/spice-qemu-char.c
index 613cc64..ba59374 100644
--- a/spice-qemu-char.c
+++ b/spice-qemu-char.c
@@ -213,16 +213,14 @@ static void spice_chr_close(struct CharDriverState *chr)
     g_free(s);
 }
 
-static void spice_chr_guest_open(struct CharDriverState *chr)
+static void spice_chr_set_fe_open(struct CharDriverState *chr, int fe_open)
 {
     SpiceCharDriver *s = chr->opaque;
-    vmc_register_interface(s);
-}
-
-static void spice_chr_guest_close(struct CharDriverState *chr)
-{
-    SpiceCharDriver *s = chr->opaque;
-    vmc_unregister_interface(s);
+    if (fe_open) {
+        vmc_register_interface(s);
+    } else {
+        vmc_unregister_interface(s);
+    }
 }
 
 static void print_allowed_subtypes(void)
@@ -256,8 +254,7 @@ static CharDriverState *chr_open(const char *subtype)
     chr->chr_write = spice_chr_write;
     chr->chr_add_watch = spice_chr_add_watch;
     chr->chr_close = spice_chr_close;
-    chr->chr_guest_open = spice_chr_guest_open;
-    chr->chr_guest_close = spice_chr_guest_close;
+    chr->chr_set_fe_open = spice_chr_set_fe_open;
 
     QLIST_INSERT_HEAD(&spice_chars, s, next);
 
-- 
1.8.1.4

[Qemu-devel] [PATCH 7/8] virtio-serial: Consolidate guest_open/guest_close into set_guest_connected

[Hans de Goede]

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
---
 hw/virtio-console.c    | 23 +++++------------------
 hw/virtio-serial-bus.c | 15 +++++----------
 hw/virtio-serial.h     |  6 ++----
 3 files changed, 12 insertions(+), 32 deletions(-)

diff --git a/hw/virtio-console.c b/hw/virtio-console.c
index c0d41c5..e28c54f 100644
--- a/hw/virtio-console.c
+++ b/hw/virtio-console.c
@@ -71,26 +71,15 @@ static ssize_t flush_buf(VirtIOSerialPort *port, const uint8_t *buf, size_t len)
     return ret;
 }
 
-/* Callback function that's called when the guest opens the port */
-static void guest_open(VirtIOSerialPort *port)
+/* Callback function that's called when the guest opens/closes the port */
+static void set_guest_connected(VirtIOSerialPort *port, int guest_connected)
 {
     VirtConsole *vcon = DO_UPCAST(VirtConsole, port, port);
 
     if (!vcon->chr) {
         return;
     }
-    qemu_chr_fe_set_open(vcon->chr, 1);
-}
-
-/* Callback function that's called when the guest closes the port */
-static void guest_close(VirtIOSerialPort *port)
-{
-    VirtConsole *vcon = DO_UPCAST(VirtConsole, port, port);
-
-    if (!vcon->chr) {
-        return;
-    }
-    qemu_chr_fe_set_open(vcon->chr, 0);
+    qemu_chr_fe_set_open(vcon->chr, guest_connected);
 }
 
 /* Readiness of the guest to accept data on a port */
@@ -173,8 +162,7 @@ static void virtconsole_class_init(ObjectClass *klass, void *data)
     k->init = virtconsole_initfn;
     k->exit = virtconsole_exitfn;
     k->have_data = flush_buf;
-    k->guest_open = guest_open;
-    k->guest_close = guest_close;
+    k->set_guest_connected = set_guest_connected;
     dc->props = virtconsole_properties;
 }
 
@@ -197,8 +185,7 @@ static void virtserialport_class_init(ObjectClass *klass, void *data)
 
     k->init = virtconsole_initfn;
     k->have_data = flush_buf;
-    k->guest_open = guest_open;
-    k->guest_close = guest_close;
+    k->set_guest_connected = set_guest_connected;
     dc->props = virtserialport_properties;
 }
 
diff --git a/hw/virtio-serial-bus.c b/hw/virtio-serial-bus.c
index ab7168e..eb7af21 100644
--- a/hw/virtio-serial-bus.c
+++ b/hw/virtio-serial-bus.c
@@ -372,14 +372,9 @@ static void handle_control_message(VirtIOSerial *vser, void *buf, size_t len)
 
     case VIRTIO_CONSOLE_PORT_OPEN:
         port->guest_connected = cpkt.value;
-        if (cpkt.value && vsc->guest_open) {
+        if (vsc->set_guest_connected) {
             /* Send the guest opened notification if an app is interested */
-            vsc->guest_open(port);
-        }
-
-        if (!cpkt.value && vsc->guest_close) {
-            /* Send the guest closed notification if an app is interested */
-            vsc->guest_close(port);
+            vsc->set_guest_connected(port, cpkt.value);
         }
         break;
     }
@@ -484,9 +479,9 @@ static void guest_reset(VirtIOSerial *vser)
         vsc = VIRTIO_SERIAL_PORT_GET_CLASS(port);
         if (port->guest_connected) {
             port->guest_connected = false;
-
-            if (vsc->guest_close)
-                vsc->guest_close(port);
+            if (vsc->set_guest_connected) {
+                vsc->set_guest_connected(port, false);
+            }
         }
     }
 }
diff --git a/hw/virtio-serial.h b/hw/virtio-serial.h
index 484dcfe..516400f 100644
--- a/hw/virtio-serial.h
+++ b/hw/virtio-serial.h
@@ -92,10 +92,8 @@ typedef struct VirtIOSerialPortClass {
     int (*exit)(VirtIOSerialPort *port);
 
     /* Callbacks for guest events */
-        /* Guest opened device. */
-    void (*guest_open)(VirtIOSerialPort *port);
-        /* Guest closed device. */
-    void (*guest_close)(VirtIOSerialPort *port);
+        /* Guest opened/closed device. */
+    void (*set_guest_connected)(VirtIOSerialPort *port, int guest_connected);
 
         /* Guest is now ready to accept data (virtqueues set up). */
     void (*guest_ready)(VirtIOSerialPort *port);
-- 
1.8.1.4

[Qemu-devel] [PATCH 8/8] spice-qemu-char: Drop hackish vmc_register on spice_chr_write

[Hans de Goede]

Now that the core takes care of fe_open tracking we no longer need this hack.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
---
 spice-qemu-char.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/spice-qemu-char.c b/spice-qemu-char.c
index ba59374..7e6bd2d 100644
--- a/spice-qemu-char.c
+++ b/spice-qemu-char.c
@@ -184,7 +184,6 @@ static int spice_chr_write(CharDriverState *chr, const uint8_t *buf, int len)
     SpiceCharDriver *s = chr->opaque;
     int read_bytes;
 
-    vmc_register_interface(s);
     assert(s->datalen == 0);
     s->datapos = buf;
     s->datalen = len;
-- 
1.8.1.4

Re: [Qemu-devel] [PATCH 1/8] RFC: chardev frontend open handling cleanup

[Alon Levy]

> This patch-series is the result of the
> "[PATCH 1/2] char: add qemu_chr_be_is_fe_connected" discussion
> thread.
> 
> This patch series (tries to) make(s) the frontend open concept both
> more
> explicit and generic, and significantly cleans up the surrounding
> code.

The whole patch series looks good to me.

> 
> Regards,
> 
> Hans
> 
>