On Fri, Sep 12, 2025 at 05:39:53AM +0200, Filip Hejsek wrote:
> From: Szymon Lukasz <[email protected]>
>
> 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 old versions of the Linux kernel
> used an incorrect order for the fields (rows then cols instead of cols
> then rows), until it was fixed by commit
> 5326ab737a47278dbd16ed3ee7380b26c7056ddd.
>
> As a result, when using a Linux kernel older than 6.15, the number of rows
> and columns will be swapped.
>
> Signed-off-by: Szymon Lukasz <[email protected]>
> Reviewed-by: Michael S. Tsirkin <[email protected]>
> Signed-off-by: Filip Hejsek <[email protected]>
> ---
> hw/char/trace-events | 1 +
> hw/char/virtio-serial-bus.c | 43
> +++++++++++++++++++++++++++++++++++++--
> hw/core/machine.c | 4 +++-
> include/hw/virtio/virtio-serial.h | 5 +++++
> 4 files changed, 50 insertions(+), 3 deletions(-)
>
> diff --git a/hw/char/trace-events b/hw/char/trace-events
> index
> 05a33036c12070242c2b193c19011839d623bec4..9a975ab1e2a525a9391d0f0a85ddbe80aa6361fc
> 100644
> --- a/hw/char/trace-events
> +++ b/hw/char/trace-events
> @@ -11,6 +11,7 @@ serial_update_parameters(uint64_t baudrate, char parity,
> int data_bits, int stop
>
> # 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
> 673c50f0be08ef9b7142c16eaf8e6e31c7a00ca5..1d2963efcd74494a1f0d428f8ace0e72bb4c6647
> 100644
> --- a/hw/char/virtio-serial-bus.c
> +++ b/hw/char/virtio-serial-bus.c
> @@ -260,6 +260,43 @@ 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 cols;
> + __virtio16 rows;
> +};
> +
> +void virtio_serial_send_console_resize(VirtIOSerialPort *port,
> + uint16_t cols, uint16_t rows)
> +{
> + VirtIOSerial *vser = port->vser;
> + VirtIODevice *vdev = VIRTIO_DEVICE(vser);
> +
> + trace_virtio_serial_send_console_resize(port->id, cols, rows);
> +
> + 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);
> +
> + 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);
IIUC, we should skip sending this if port->id does NOT reflect
the primary port 0, as the virtio spec indicates F_SIZE only
applies to port 0 unless we have F_MULTIPORT set.
> + }
> +}
> +
> /* Functions for use inside qemu to open and read from/write to ports */
> int virtio_serial_open(VirtIOSerialPort *port)
> {
> @@ -571,8 +608,8 @@ 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);
> }
> @@ -1158,6 +1195,8 @@ static const Property virtio_serial_properties[] = {
> 31),
> DEFINE_PROP_BIT64("emergency-write", VirtIOSerial, host_features,
> VIRTIO_CONSOLE_F_EMERG_WRITE, true),
> + DEFINE_PROP_BIT64("console-size", VirtIOSerial, host_features,
> + VIRTIO_CONSOLE_F_SIZE, true),
> };
>
> static void virtio_serial_class_init(ObjectClass *klass, const void *data)
> diff --git a/hw/core/machine.c b/hw/core/machine.c
> index
> 38c949c4f2ce4a117cbfca62f56919711ce392b4..74a747ec6578c958b35e1f9712e5dbed7bca72e8
> 100644
> --- a/hw/core/machine.c
> +++ b/hw/core/machine.c
> @@ -37,7 +37,9 @@
> #include "hw/virtio/virtio-iommu.h"
> #include "audio/audio.h"
>
> -GlobalProperty hw_compat_10_1[] = {};
> +GlobalProperty hw_compat_10_1[] = {
> + { "virtio-serial-device", "console-size", "off" },
> +};
> const size_t hw_compat_10_1_len = G_N_ELEMENTS(hw_compat_10_1);
>
> GlobalProperty hw_compat_10_0[] = {
> diff --git a/include/hw/virtio/virtio-serial.h
> b/include/hw/virtio/virtio-serial.h
> index
> d87c62eab7a270809daf47f932a73dd1fa3d5a6e..81efa853f804a52866890a9ec2c71bfbcabca4a0
> 100644
> --- a/include/hw/virtio/virtio-serial.h
> +++ b/include/hw/virtio/virtio-serial.h
> @@ -187,6 +187,8 @@ struct VirtIOSerial {
> virtio_serial_conf serial;
>
> uint64_t host_features;
> +
> + uint16_t port0_cols, port0_rows;
> };
>
> /* Interface to the virtio-serial bus */
> @@ -221,6 +223,9 @@ 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"
> OBJECT_DECLARE_SIMPLE_TYPE(VirtIOSerial, VIRTIO_SERIAL)
>
>
> --
> 2.51.0
>
>
With regards,
Daniel
--
|: https://berrange.com -o- https://www.flickr.com/photos/dberrange :|
|: https://libvirt.org -o- https://fstop138.berrange.com :|
|: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|
