From: Szymon Lukasz <noh4hss@gmail.com>
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 <noh4hss@gmail.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Filip Hejsek <filip.hejsek@gmail.com>
---
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);
+ }
+}
+
/* 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)
--
2.51.0On Fri, Sep 12, 2025 at 05:39:53AM +0200, Filip Hejsek wrote:
> From: Szymon Lukasz <noh4hss@gmail.com>
>
> 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 <noh4hss@gmail.com>
> Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
> Signed-off-by: Filip Hejsek <filip.hejsek@gmail.com>
> ---
> 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
--
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On September 18, 2025 10:23:33 AM GMT+02:00, "Daniel P. Berrangé" <berrange@redhat.com> wrote:
> On Fri, Sep 12, 2025 at 05:39:53AM +0200, Filip Hejsek wrote:
> > From: Szymon Lukasz <noh4hss@gmail.com>
> >
> > 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 <noh4hss@gmail.com>
> > Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
> > Signed-off-by: Filip Hejsek <filip.hejsek@gmail.com>
> > ---
> > [...]
> > + 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.
I have already changed this in my working version. I'm on a phone
and don't have access to it right now, but it was something like this pseudocode:
if "console-size" enabled:
if port id == 0:
port0_{cols,rows} = {cols,rows}
if multiport:
send VIRTIO_CONSOLE_RESIZE
else:
notify config
I guess I should make the config notification conditional on port 0 too.
Filip Hejsek <filip.hejsek@gmail.com> writes: > From: Szymon Lukasz <noh4hss@gmail.com> > > 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. Should this note be added to user documentation? > Signed-off-by: Szymon Lukasz <noh4hss@gmail.com> > Reviewed-by: Michael S. Tsirkin <mst@redhat.com> > Signed-off-by: Filip Hejsek <filip.hejsek@gmail.com>
On Fri, 2025-09-12 at 15:50 +0200, Markus Armbruster wrote: > > As a result, when using a Linux kernel older than 6.15, the number of rows > > and columns will be swapped. > > Should this note be added to user documentation? Agreed, but I want first to reach a decision about how to deal with compatibility with older kernels (e.g. option to disable the feature, option to swap the fields, etc), plus the Linux patch may end up being reverted so I want to wait until that is decided.
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