Implement the part of the virtio spec that allows to notify the virtio
driver about terminal resizes. The virtio spec contains two methods to
achieve that:

For legacy drivers, we have only one port and we put the terminal size
in the config space and inject the config changed interrupt.

For multiport devices, we use the control virtqueue to send a packet
containing the terminal size. Note that the Linux kernel expects
the fields indicating the number of rows and columns in a packet to be
in a different order than the one specified in the current version of
the virtio spec. We follow the Linux implementation, so hopefully there
is no implementation of this functionality conforming to the spec.

Signed-off-by: Szymon Lukasz <noh4hss@gmail.com>
---
 hw/char/trace-events              |  1 +
 hw/char/virtio-serial-bus.c       | 41 +++++++++++++++++++++++++++++--
 include/hw/virtio/virtio-serial.h |  5 ++++
 3 files changed, 45 insertions(+), 2 deletions(-)

diff --git a/hw/char/trace-events b/hw/char/trace-events
index d20eafd56f..be40df47ea 100644
--- a/hw/char/trace-events
+++ b/hw/char/trace-events
@@ -10,6 +10,7 @@ serial_ioport_write(uint16_t addr, uint8_t value) "write addr 0x%02x val 0x%02x"
 
 # virtio-serial-bus.c
 virtio_serial_send_control_event(unsigned int port, uint16_t event, uint16_t value) "port %u, event %u, value %u"
+virtio_serial_send_console_resize(unsigned int port, uint16_t cols, uint16_t rows) "port %u, cols %u, rows %u"
 virtio_serial_throttle_port(unsigned int port, bool throttle) "port %u, throttle %d"
 virtio_serial_handle_control_message(uint16_t event, uint16_t value) "event %u, value %u"
 virtio_serial_handle_control_message_port(unsigned int port) "port %u"
diff --git a/hw/char/virtio-serial-bus.c b/hw/char/virtio-serial-bus.c
index 262089c0c9..9d99161e13 100644
--- a/hw/char/virtio-serial-bus.c
+++ b/hw/char/virtio-serial-bus.c
@@ -261,6 +261,42 @@ static size_t send_control_event(VirtIOSerial *vser, uint32_t port_id,
     return send_control_msg(vser, &cpkt, sizeof(cpkt));
 }
 
+/*
+ * This struct should be added to the Linux kernel uapi headers
+ * and later imported to standard-headers/linux/virtio_console.h
+ */
+struct virtio_console_resize {
+    __virtio16 rows;
+    __virtio16 cols;
+};
+
+void virtio_serial_send_console_resize(VirtIOSerialPort *port,
+                                       uint16_t cols, uint16_t rows)
+{
+    VirtIOSerial *vser = port->vser;
+    VirtIODevice *vdev = VIRTIO_DEVICE(vser);
+
+    if (virtio_vdev_has_feature(vdev, VIRTIO_CONSOLE_F_MULTIPORT)) {
+        struct {
+            struct virtio_console_control control;
+            struct virtio_console_resize resize;
+        } buffer;
+
+        virtio_stl_p(vdev, &buffer.control.id, port->id);
+        virtio_stw_p(vdev, &buffer.control.event, VIRTIO_CONSOLE_RESIZE);
+        virtio_stw_p(vdev, &buffer.resize.cols, cols);
+        virtio_stw_p(vdev, &buffer.resize.rows, rows);
+
+        trace_virtio_serial_send_console_resize(port->id, cols, rows);
+        send_control_msg(vser, &buffer, sizeof(buffer));
+
+    } else if (virtio_vdev_has_feature(vdev, VIRTIO_CONSOLE_F_SIZE)) {
+        vser->port0_cols = cols;
+        vser->port0_rows = rows;
+        virtio_notify_config(vdev);
+    }
+}
+
 /* Functions for use inside qemu to open and read from/write to ports */
 int virtio_serial_open(VirtIOSerialPort *port)
 {
@@ -559,6 +595,7 @@ static uint64_t get_features(VirtIODevice *vdev, uint64_t features,
     vser = VIRTIO_SERIAL(vdev);
 
     features |= vser->host_features;
+    virtio_add_feature(&features, VIRTIO_CONSOLE_F_SIZE);
     if (vser->bus.max_nr_ports > 1) {
         virtio_add_feature(&features, VIRTIO_CONSOLE_F_MULTIPORT);
     }
@@ -572,8 +609,8 @@ static void get_config(VirtIODevice *vdev, uint8_t *config_data)
     struct virtio_console_config *config =
         (struct virtio_console_config *)config_data;
 
-    config->cols = 0;
-    config->rows = 0;
+    config->cols = virtio_tswap16(vdev, vser->port0_cols);
+    config->rows = virtio_tswap16(vdev, vser->port0_rows);
     config->max_nr_ports = virtio_tswap32(vdev,
                                           vser->serial.max_virtserial_ports);
 }
diff --git a/include/hw/virtio/virtio-serial.h b/include/hw/virtio/virtio-serial.h
index ed3e916b68..1d6436c0b1 100644
--- a/include/hw/virtio/virtio-serial.h
+++ b/include/hw/virtio/virtio-serial.h
@@ -188,6 +188,8 @@ struct VirtIOSerial {
     virtio_serial_conf serial;
 
     uint64_t host_features;
+
+    uint16_t port0_cols, port0_rows;
 };
 
 /* Interface to the virtio-serial bus */
@@ -222,6 +224,9 @@ size_t virtio_serial_guest_ready(VirtIOSerialPort *port);
  */
 void virtio_serial_throttle_port(VirtIOSerialPort *port, bool throttle);
 
+void virtio_serial_send_console_resize(VirtIOSerialPort *port,
+                                       uint16_t cols, uint16_t rows);
+
 #define TYPE_VIRTIO_SERIAL "virtio-serial-device"
 #define VIRTIO_SERIAL(obj) \
         OBJECT_CHECK(VirtIOSerial, (obj), TYPE_VIRTIO_SERIAL)
-- 
2.27.0

On Sun, Jun 21, 2020 at 06:21:31PM +0200, Szymon Lukasz wrote:
> Implement the part of the virtio spec that allows to notify the virtio
> driver about terminal resizes. The virtio spec contains two methods to
> achieve that:
> 
> For legacy drivers, we have only one port and we put the terminal size
> in the config space and inject the config changed interrupt.
> 
> For multiport devices, we use the control virtqueue to send a packet
> containing the terminal size. Note that the Linux kernel expects
> the fields indicating the number of rows and columns in a packet to be
> in a different order than the one specified in the current version of
> the virtio spec. We follow the Linux implementation, so hopefully there
> is no implementation of this functionality conforming to the spec.
> 
> Signed-off-by: Szymon Lukasz <noh4hss@gmail.com>
> ---
>  hw/char/trace-events              |  1 +
>  hw/char/virtio-serial-bus.c       | 41 +++++++++++++++++++++++++++++--
>  include/hw/virtio/virtio-serial.h |  5 ++++
>  3 files changed, 45 insertions(+), 2 deletions(-)
> 
> diff --git a/hw/char/trace-events b/hw/char/trace-events
> index d20eafd56f..be40df47ea 100644
> --- a/hw/char/trace-events
> +++ b/hw/char/trace-events
> @@ -10,6 +10,7 @@ serial_ioport_write(uint16_t addr, uint8_t value) "write addr 0x%02x val 0x%02x"
>  
>  # virtio-serial-bus.c
>  virtio_serial_send_control_event(unsigned int port, uint16_t event, uint16_t value) "port %u, event %u, value %u"
> +virtio_serial_send_console_resize(unsigned int port, uint16_t cols, uint16_t rows) "port %u, cols %u, rows %u"
>  virtio_serial_throttle_port(unsigned int port, bool throttle) "port %u, throttle %d"
>  virtio_serial_handle_control_message(uint16_t event, uint16_t value) "event %u, value %u"
>  virtio_serial_handle_control_message_port(unsigned int port) "port %u"
> diff --git a/hw/char/virtio-serial-bus.c b/hw/char/virtio-serial-bus.c
> index 262089c0c9..9d99161e13 100644
> --- a/hw/char/virtio-serial-bus.c
> +++ b/hw/char/virtio-serial-bus.c
> @@ -261,6 +261,42 @@ static size_t send_control_event(VirtIOSerial *vser, uint32_t port_id,
>      return send_control_msg(vser, &cpkt, sizeof(cpkt));
>  }
>  
> +/*
> + * This struct should be added to the Linux kernel uapi headers
> + * and later imported to standard-headers/linux/virtio_console.h
> + */
> +struct virtio_console_resize {
> +    __virtio16 rows;
> +    __virtio16 cols;
> +};
> +
> +void virtio_serial_send_console_resize(VirtIOSerialPort *port,
> +                                       uint16_t cols, uint16_t rows)
> +{
> +    VirtIOSerial *vser = port->vser;
> +    VirtIODevice *vdev = VIRTIO_DEVICE(vser);
> +
> +    if (virtio_vdev_has_feature(vdev, VIRTIO_CONSOLE_F_MULTIPORT)) {
> +        struct {
> +            struct virtio_console_control control;
> +            struct virtio_console_resize resize;
> +        } buffer;
> +
> +        virtio_stl_p(vdev, &buffer.control.id, port->id);
> +        virtio_stw_p(vdev, &buffer.control.event, VIRTIO_CONSOLE_RESIZE);
> +        virtio_stw_p(vdev, &buffer.resize.cols, cols);
> +        virtio_stw_p(vdev, &buffer.resize.rows, rows);
> +
> +        trace_virtio_serial_send_console_resize(port->id, cols, rows);
> +        send_control_msg(vser, &buffer, sizeof(buffer));
> +
> +    } else if (virtio_vdev_has_feature(vdev, VIRTIO_CONSOLE_F_SIZE)) {
> +        vser->port0_cols = cols;
> +        vser->port0_rows = rows;
> +        virtio_notify_config(vdev);
> +    }
> +}
> +
>  /* Functions for use inside qemu to open and read from/write to ports */
>  int virtio_serial_open(VirtIOSerialPort *port)
>  {
> @@ -559,6 +595,7 @@ static uint64_t get_features(VirtIODevice *vdev, uint64_t features,
>      vser = VIRTIO_SERIAL(vdev);
>  
>      features |= vser->host_features;
> +    virtio_add_feature(&features, VIRTIO_CONSOLE_F_SIZE);
>      if (vser->bus.max_nr_ports > 1) {
>          virtio_add_feature(&features, VIRTIO_CONSOLE_F_MULTIPORT);
>      }

Unconditonally adding a feature bit like that will break cross-version
migration. You need to add it through a bit property and
the disable for existing machine types.


> @@ -572,8 +609,8 @@ static void get_config(VirtIODevice *vdev, uint8_t *config_data)
>      struct virtio_console_config *config =
>          (struct virtio_console_config *)config_data;
>  
> -    config->cols = 0;
> -    config->rows = 0;
> +    config->cols = virtio_tswap16(vdev, vser->port0_cols);
> +    config->rows = virtio_tswap16(vdev, vser->port0_rows);
>      config->max_nr_ports = virtio_tswap32(vdev,
>                                            vser->serial.max_virtserial_ports);
>  }
> diff --git a/include/hw/virtio/virtio-serial.h b/include/hw/virtio/virtio-serial.h
> index ed3e916b68..1d6436c0b1 100644
> --- a/include/hw/virtio/virtio-serial.h
> +++ b/include/hw/virtio/virtio-serial.h
> @@ -188,6 +188,8 @@ struct VirtIOSerial {
>      virtio_serial_conf serial;
>  
>      uint64_t host_features;
> +
> +    uint16_t port0_cols, port0_rows;
>  };
>  
>  /* Interface to the virtio-serial bus */
> @@ -222,6 +224,9 @@ size_t virtio_serial_guest_ready(VirtIOSerialPort *port);
>   */
>  void virtio_serial_throttle_port(VirtIOSerialPort *port, bool throttle);
>  
> +void virtio_serial_send_console_resize(VirtIOSerialPort *port,
> +                                       uint16_t cols, uint16_t rows);
> +
>  #define TYPE_VIRTIO_SERIAL "virtio-serial-device"
>  #define VIRTIO_SERIAL(obj) \
>          OBJECT_CHECK(VirtIOSerial, (obj), TYPE_VIRTIO_SERIAL)
> -- 
> 2.27.0