[PATCH v10 00/12] virtio-console: notify about the terminal size

[PATCH v10 00/12] virtio-console: notify about the terminal size

[Filip Hejsek]

Summary of the Series
---------------------

This series adds terminal size support to the virtio-console device.
The goal is to make it possible to get a resizable terminal into a guest
without using e.g. ssh.

Support for detecting terminal size is added to stdio and vc backends,
but not pty and serial, because for the later it's unfortunately
impossible to get resize notifications.

A QMP command is added for notifying QEMU about the terminal size
of any chardev. This can be used by clients to support resizing for
devices where QEMU is not able to detect the size by itself (e.g. virsh
console).

There was a bug in Linux versions prior to 6.15 which caused the
dimensions to be interpreted incorrectly by the guest. The fix has
been backported to currently supported kernels, but to avoid making the
terminal harder to use on out of date guests, the feature is disabled
by default and must be enabled with the console-size property.

Limitations
-----------

There is no documentation for the virtio-serial device. I'm working on
this and will submit it separately.

Resizing support for the spice version of 'vc' chardev is still missing.

After migration, the guest is not informed about the new console size.
I propably won't fix this any time soon unless someone helps me with
migration stream changes.

Full Changelog
--------------

v10:
- Fix build error on win32
- Link to v9: https://lore.kernel.org/qemu-devel/20261012-console-resize-v9-0-8db78320ba81@gmail.com

v9:
- Clean up SIGWINCH notifier when stdio or curses chardev is destroyed
- Link to v8: https://lore.kernel.org/qemu-devel/20260929-console-resize-v8-0-2ff9183f8750@gmail.com

v8:
- Rebased
- Fixed uninitialized buffer in send_console_resize
- "Since: 11.1" -> "Since: 11.2"
- Link to v7: https://lore.kernel.org/qemu-devel/20260609-console-resize-v7-0-0c550fdcec15@gmail.com

v7:
- Rebased
- Renamed some functions
- Made virtio size support disabled by default
- "Since: 11.0" -> "Since: 11.1"
- Dropped "must exist" from chardev id param description in qmp docs
- Link to v6: https://lore.kernel.org/qemu-devel/20260119-console-resize-v6-0-33a7b0330a7a@gmail.com

v6:
- Rebased (renaming CharBackend -> CharFrontend)
- Virtio resize message code rewritten to fix corner cases
- Updated version numbers ('Since: 11.0', hw_compat_10_2)
- Added note to CHR_EVENT_RESIZE definition comment, explaining
  that only the focused frontend gets the event
- Fixed checkpatch warning (line length)
- Link to v5: https://lore.kernel.org/qemu-devel/20250921-console-resize-v5-0-89e3c6727060@gmail.com

v5:
- Rename chardev-resize -> chardev-window-size-changed
- Improve chardev-window-size-changed documentation
- Add partial implementation for 'vc' chardev
- Config space now returns port 0 size if multiport
- Console-size property completely disables size support
- Fix misnamed variables in char-win-stdio
- Link to v4: https://lore.kernel.org/qemu-devel/20250912-console-resize-v4-0-7925e444afc4@gmail.com

v4:
- Changed order of rows and cols fields
- Added support for terminal size on Windows
- Trace event is also emitted for legacy (non-multiport) drivers
- Minor fixes required because of changes in QEMU (DECLARE_INSTANCE_CHECKER, qmp-example)
- Updated version numbers ('Since: 10.2', hw_compat_10_1)
- Link to v3: https://lore.kernel.org/qemu-devel/20200629164041.472528-1-noh4hss@gmail.com

v3:
- Add resize messages over QMP, as suggested by Daniel

v2:
- Fix adding a new virtio feature bit to the virtio console device

---
Filip Hejsek (4):
      char-win-stdio: add support for terminal size
      ui/console-vc: forward text console size to vc chardev
      ui/gtk: forward gtk console size to vc chardev
      virtio-serial-bus: add terminal resize messages

Szymon Lukasz (8):
      chardev: add cols, rows fields
      chardev: add CHR_EVENT_RESIZE
      chardev: add qemu_chr_resize()
      char-mux: add support for the terminal size
      main-loop: change the handling of SIGWINCH
      char-stdio: add support for the terminal size
      qmp: add chardev-window-size-changed command
      virtio-console: notify the guest about terminal resizes

 backends/cryptodev-vhost-user.c   |  1 +
 chardev/char-fe.c                 | 13 +++++++
 chardev/char-mux.c                | 19 ++++++++-
 chardev/char-stdio.c              | 33 ++++++++++++++++
 chardev/char-win-stdio.c          | 19 +++++++++
 chardev/char.c                    | 26 +++++++++++++
 hw/block/vhost-user-blk.c         |  1 +
 hw/char/terminal3270.c            |  1 +
 hw/char/trace-events              |  1 +
 hw/char/virtio-console.c          | 35 +++++++++++++++--
 hw/char/virtio-serial-bus.c       | 81 ++++++++++++++++++++++++++++++++++++++-
 hw/display/vhost-user-media.c     |  1 +
 hw/ipmi/ipmi_bmc_extern.c         |  1 +
 hw/scsi/vhost-user-scsi.c         |  1 +
 hw/usb/ccid-card-passthru.c       |  1 +
 hw/usb/dev-serial.c               |  1 +
 hw/usb/redirect.c                 |  1 +
 hw/virtio/vhost-user-base.c       |  1 +
 hw/virtio/vhost-user-scmi.c       |  1 +
 include/chardev/char-fe.h         | 10 +++++
 include/chardev/char.h            |  9 +++++
 include/hw/virtio/virtio-serial.h |  7 ++++
 include/qemu/main-loop.h          |  5 +++
 monitor/hmp.c                     |  1 +
 monitor/qmp.c                     |  1 +
 net/passt.c                       |  1 +
 net/vhost-user.c                  |  1 +
 qapi/char.json                    | 31 +++++++++++++++
 ui/console-vc.c                   |  8 ++++
 ui/curses.c                       | 21 +++++++---
 ui/gtk.c                          | 28 ++++++++++++++
 util/main-loop.c                  | 33 ++++++++++++++++
 32 files changed, 382 insertions(+), 12 deletions(-)
---
base-commit: 615ece3c406b262996e569f29ea6eed0d81c4d8d
change-id: 20250912-console-resize-96c42140ba08

Best regards,
--  
Filip Hejsek <filip.hejsek@gmail.com>

[PATCH v10 01/12] chardev: add cols, rows fields

[Filip Hejsek]

From: Szymon Lukasz <noh4hss@gmail.com>

These fields should be interpreted as the size of the terminal connected
to a given chardev.

Signed-off-by: Szymon Lukasz <noh4hss@gmail.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
[Filip: CharBackend -> CharFrontend]
Signed-off-by: Filip Hejsek <filip.hejsek@gmail.com>
---
 chardev/char-fe.c         | 13 +++++++++++++
 include/chardev/char-fe.h | 10 ++++++++++
 include/chardev/char.h    |  1 +
 3 files changed, 24 insertions(+)

diff --git a/chardev/char-fe.c b/chardev/char-fe.c
index a44f267373..c61c91f779 100644
--- a/chardev/char-fe.c
+++ b/chardev/char-fe.c
@@ -329,6 +329,19 @@ void qemu_chr_fe_set_echo(CharFrontend *c, bool echo)
     }
 }
 
+void qemu_chr_fe_get_winsize(CharFrontend *c, uint16_t *cols, uint16_t *rows)
+{
+    Chardev *chr = c->chr;
+
+    if (chr) {
+        *cols = chr->cols;
+        *rows = chr->rows;
+    } else {
+        *cols = 0;
+        *rows = 0;
+    }
+}
+
 void qemu_chr_fe_set_open(CharFrontend *c, bool is_open)
 {
     Chardev *chr = c->chr;
diff --git a/include/chardev/char-fe.h b/include/chardev/char-fe.h
index a82894e1d5..e4a3801e7d 100644
--- a/include/chardev/char-fe.h
+++ b/include/chardev/char-fe.h
@@ -168,6 +168,16 @@ int qemu_chr_fe_wait_connected(CharFrontend *c, Error **errp);
  */
 void qemu_chr_fe_set_echo(CharFrontend *c, bool echo);
 
+/**
+ * qemu_chr_fe_get_winsize:
+ * @cols: the address for storing columns
+ * @rows: the address for storing rows
+ *
+ * Get the size of the terminal connected to the chardev backend.
+ * Returns *cols = *rows = 0, if no associated Chardev.
+ */
+void qemu_chr_fe_get_winsize(CharFrontend *c, uint16_t *cols, uint16_t *rows);
+
 /**
  * qemu_chr_fe_set_open:
  * @c: a CharFrontend
diff --git a/include/chardev/char.h b/include/chardev/char.h
index 7377d8e60a..6394ec2ffe 100644
--- a/include/chardev/char.h
+++ b/include/chardev/char.h
@@ -66,6 +66,7 @@ struct Chardev {
     bool logtimestamp;
     bool log_line_start;
     int be_open;
+    uint16_t cols, rows;
     /* used to coordinate the chardev-change special-case: */
     bool handover_yank_instance;
     GSource *gsource;

-- 
2.56.0

[PATCH v10 02/12] chardev: add CHR_EVENT_RESIZE

[Filip Hejsek]

From: Szymon Lukasz <noh4hss@gmail.com>

Add a new chardev event, CHR_EVENT_RESIZE, which a backend should
trigger if it detects the size of the connected terminal changed.

Signed-off-by: Szymon Lukasz <noh4hss@gmail.com>
[Filip: add note that only the focused frontend gets the event]
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Signed-off-by: Filip Hejsek <filip.hejsek@gmail.com>
---
 backends/cryptodev-vhost-user.c | 1 +
 chardev/char.c                  | 1 +
 hw/block/vhost-user-blk.c       | 1 +
 hw/char/terminal3270.c          | 1 +
 hw/char/virtio-console.c        | 1 +
 hw/display/vhost-user-media.c   | 1 +
 hw/ipmi/ipmi_bmc_extern.c       | 1 +
 hw/scsi/vhost-user-scsi.c       | 1 +
 hw/usb/ccid-card-passthru.c     | 1 +
 hw/usb/dev-serial.c             | 1 +
 hw/usb/redirect.c               | 1 +
 hw/virtio/vhost-user-base.c     | 1 +
 hw/virtio/vhost-user-scmi.c     | 1 +
 include/chardev/char.h          | 6 ++++++
 monitor/hmp.c                   | 1 +
 monitor/qmp.c                   | 1 +
 net/passt.c                     | 1 +
 net/vhost-user.c                | 1 +
 18 files changed, 23 insertions(+)

diff --git a/backends/cryptodev-vhost-user.c b/backends/cryptodev-vhost-user.c
index 3334e280a2..b0e325e47e 100644
--- a/backends/cryptodev-vhost-user.c
+++ b/backends/cryptodev-vhost-user.c
@@ -173,6 +173,7 @@ static void cryptodev_vhost_user_event(void *opaque, QEMUChrEvent event)
     case CHR_EVENT_BREAK:
     case CHR_EVENT_MUX_IN:
     case CHR_EVENT_MUX_OUT:
+    case CHR_EVENT_RESIZE:
         /* Ignore */
         break;
     }
diff --git a/chardev/char.c b/chardev/char.c
index 9da0911e50..40d2180ce7 100644
--- a/chardev/char.c
+++ b/chardev/char.c
@@ -75,6 +75,7 @@ void qemu_chr_be_event(Chardev *s, QEMUChrEvent event)
     case CHR_EVENT_BREAK:
     case CHR_EVENT_MUX_IN:
     case CHR_EVENT_MUX_OUT:
+    case CHR_EVENT_RESIZE:
         /* Ignore */
         break;
     }
diff --git a/hw/block/vhost-user-blk.c b/hw/block/vhost-user-blk.c
index 3dade143c9..1352a0cf57 100644
--- a/hw/block/vhost-user-blk.c
+++ b/hw/block/vhost-user-blk.c
@@ -441,6 +441,7 @@ static void vhost_user_blk_event(void *opaque, QEMUChrEvent event)
     case CHR_EVENT_BREAK:
     case CHR_EVENT_MUX_IN:
     case CHR_EVENT_MUX_OUT:
+    case CHR_EVENT_RESIZE:
         /* Ignore */
         break;
     }
diff --git a/hw/char/terminal3270.c b/hw/char/terminal3270.c
index 989b6f6ee1..acd754bcfa 100644
--- a/hw/char/terminal3270.c
+++ b/hw/char/terminal3270.c
@@ -169,6 +169,7 @@ static void chr_event(void *opaque, QEMUChrEvent event)
     case CHR_EVENT_BREAK:
     case CHR_EVENT_MUX_IN:
     case CHR_EVENT_MUX_OUT:
+    case CHR_EVENT_RESIZE:
         /* Ignore */
         break;
     }
diff --git a/hw/char/virtio-console.c b/hw/char/virtio-console.c
index 4737b9a56e..36ad2ddc3f 100644
--- a/hw/char/virtio-console.c
+++ b/hw/char/virtio-console.c
@@ -165,6 +165,7 @@ static void chr_event(void *opaque, QEMUChrEvent event)
     case CHR_EVENT_BREAK:
     case CHR_EVENT_MUX_IN:
     case CHR_EVENT_MUX_OUT:
+    case CHR_EVENT_RESIZE:
         /* Ignore */
         break;
     }
diff --git a/hw/display/vhost-user-media.c b/hw/display/vhost-user-media.c
index 851af8ddc2..3d76aaba58 100644
--- a/hw/display/vhost-user-media.c
+++ b/hw/display/vhost-user-media.c
@@ -241,6 +241,7 @@ static void vu_media_event(void *opaque, QEMUChrEvent event)
     case CHR_EVENT_BREAK:
     case CHR_EVENT_MUX_IN:
     case CHR_EVENT_MUX_OUT:
+    case CHR_EVENT_RESIZE:
         /* Ignore */
         break;
     }
diff --git a/hw/ipmi/ipmi_bmc_extern.c b/hw/ipmi/ipmi_bmc_extern.c
index fa08ed6c21..bd7c61b2d2 100644
--- a/hw/ipmi/ipmi_bmc_extern.c
+++ b/hw/ipmi/ipmi_bmc_extern.c
@@ -436,6 +436,7 @@ static void chr_event(void *opaque, QEMUChrEvent event)
     case CHR_EVENT_BREAK:
     case CHR_EVENT_MUX_IN:
     case CHR_EVENT_MUX_OUT:
+    case CHR_EVENT_RESIZE:
         /* Ignore */
         break;
     }
diff --git a/hw/scsi/vhost-user-scsi.c b/hw/scsi/vhost-user-scsi.c
index 5070178dc2..7687f2804f 100644
--- a/hw/scsi/vhost-user-scsi.c
+++ b/hw/scsi/vhost-user-scsi.c
@@ -225,6 +225,7 @@ static void vhost_user_scsi_event(void *opaque, QEMUChrEvent event)
     case CHR_EVENT_BREAK:
     case CHR_EVENT_MUX_IN:
     case CHR_EVENT_MUX_OUT:
+    case CHR_EVENT_RESIZE:
         /* Ignore */
         break;
     }
diff --git a/hw/usb/ccid-card-passthru.c b/hw/usb/ccid-card-passthru.c
index 5ab7855272..3f4052ec82 100644
--- a/hw/usb/ccid-card-passthru.c
+++ b/hw/usb/ccid-card-passthru.c
@@ -323,6 +323,7 @@ static void ccid_card_vscard_event(void *opaque, QEMUChrEvent event)
     case CHR_EVENT_MUX_IN:
     case CHR_EVENT_MUX_OUT:
     case CHR_EVENT_CLOSED:
+    case CHR_EVENT_RESIZE:
         /* Ignore */
         break;
     }
diff --git a/hw/usb/dev-serial.c b/hw/usb/dev-serial.c
index b238cb7937..98d2abbd56 100644
--- a/hw/usb/dev-serial.c
+++ b/hw/usb/dev-serial.c
@@ -576,6 +576,7 @@ static void usb_serial_event(void *opaque, QEMUChrEvent event)
         break;
     case CHR_EVENT_MUX_IN:
     case CHR_EVENT_MUX_OUT:
+    case CHR_EVENT_RESIZE:
         /* Ignore */
         break;
     }
diff --git a/hw/usb/redirect.c b/hw/usb/redirect.c
index dfd9e8bb50..a666b1e8d7 100644
--- a/hw/usb/redirect.c
+++ b/hw/usb/redirect.c
@@ -1390,6 +1390,7 @@ static void usbredir_chardev_event(void *opaque, QEMUChrEvent event)
     case CHR_EVENT_BREAK:
     case CHR_EVENT_MUX_IN:
     case CHR_EVENT_MUX_OUT:
+    case CHR_EVENT_RESIZE:
         /* Ignore */
         break;
     }
diff --git a/hw/virtio/vhost-user-base.c b/hw/virtio/vhost-user-base.c
index 1a377016e7..3cb59fc173 100644
--- a/hw/virtio/vhost-user-base.c
+++ b/hw/virtio/vhost-user-base.c
@@ -277,6 +277,7 @@ static void vub_event(void *opaque, QEMUChrEvent event)
     case CHR_EVENT_BREAK:
     case CHR_EVENT_MUX_IN:
     case CHR_EVENT_MUX_OUT:
+    case CHR_EVENT_RESIZE:
         /* Ignore */
         break;
     }
diff --git a/hw/virtio/vhost-user-scmi.c b/hw/virtio/vhost-user-scmi.c
index c4692bd6aa..29d37716b3 100644
--- a/hw/virtio/vhost-user-scmi.c
+++ b/hw/virtio/vhost-user-scmi.c
@@ -215,6 +215,7 @@ static void vu_scmi_event(void *opaque, QEMUChrEvent event)
     case CHR_EVENT_BREAK:
     case CHR_EVENT_MUX_IN:
     case CHR_EVENT_MUX_OUT:
+    case CHR_EVENT_RESIZE:
         /* Ignore */
         break;
     }
diff --git a/include/chardev/char.h b/include/chardev/char.h
index 6394ec2ffe..ee9f24038b 100644
--- a/include/chardev/char.h
+++ b/include/chardev/char.h
@@ -22,6 +22,12 @@ typedef enum {
     CHR_EVENT_OPENED, /* new connection established */
     CHR_EVENT_MUX_IN, /* mux-focus was set to this terminal */
     CHR_EVENT_MUX_OUT, /* mux-focus will move on */
+    CHR_EVENT_RESIZE, /*
+                       * the size of the terminal connected to
+                       * the chardev has changed.  NOTE: this event is only
+                       * sent to the focused frontend, so you should also
+                       * update the size on receiving CHR_EVENT_MUX_IN.
+                       */
     CHR_EVENT_CLOSED /* connection closed.  NOTE: currently this event
                       * is only bound to the read port of the chardev.
                       * Normally the read port and write port of a
diff --git a/monitor/hmp.c b/monitor/hmp.c
index 488ec23937..7b80d84800 100644
--- a/monitor/hmp.c
+++ b/monitor/hmp.c
@@ -1587,6 +1587,7 @@ static void monitor_event(void *opaque, QEMUChrEvent event)
         break;
 
     case CHR_EVENT_BREAK:
+    case CHR_EVENT_RESIZE:
         /* Ignored */
         break;
     }
diff --git a/monitor/qmp.c b/monitor/qmp.c
index aec0315775..eb44012643 100644
--- a/monitor/qmp.c
+++ b/monitor/qmp.c
@@ -663,6 +663,7 @@ static void monitor_qmp_event(void *opaque, QEMUChrEvent event)
     case CHR_EVENT_BREAK:
     case CHR_EVENT_MUX_IN:
     case CHR_EVENT_MUX_OUT:
+    case CHR_EVENT_RESIZE:
         /* Ignore */
         break;
     }
diff --git a/net/passt.c b/net/passt.c
index 45440c399b..e65198960e 100644
--- a/net/passt.c
+++ b/net/passt.c
@@ -428,6 +428,7 @@ static void passt_vhost_user_event(void *opaque, QEMUChrEvent event)
     case CHR_EVENT_BREAK:
     case CHR_EVENT_MUX_IN:
     case CHR_EVENT_MUX_OUT:
+    case CHR_EVENT_RESIZE:
         /* Ignore */
         break;
     }
diff --git a/net/vhost-user.c b/net/vhost-user.c
index 2d0fc49b4d..b849de92da 100644
--- a/net/vhost-user.c
+++ b/net/vhost-user.c
@@ -363,6 +363,7 @@ static void net_vhost_user_event(void *opaque, QEMUChrEvent event)
     case CHR_EVENT_BREAK:
     case CHR_EVENT_MUX_IN:
     case CHR_EVENT_MUX_OUT:
+    case CHR_EVENT_RESIZE:
         /* Ignore */
         break;
     }

-- 
2.56.0

[PATCH v10 03/12] chardev: add qemu_chr_resize()

[Filip Hejsek]

From: Szymon Lukasz <noh4hss@gmail.com>

This function should be called whenever we learn about a new size of
the terminal connected to a chardev.

Signed-off-by: Szymon Lukasz <noh4hss@gmail.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Signed-off-by: Filip Hejsek <filip.hejsek@gmail.com>
---
 chardev/char.c         | 11 +++++++++++
 include/chardev/char.h |  2 ++
 2 files changed, 13 insertions(+)

diff --git a/chardev/char.c b/chardev/char.c
index 40d2180ce7..8c8386e5b5 100644
--- a/chardev/char.c
+++ b/chardev/char.c
@@ -386,6 +386,17 @@ int qemu_chr_wait_connected(Chardev *chr, Error **errp)
     return 0;
 }
 
+void qemu_chr_resize(Chardev *chr, uint16_t cols, uint16_t rows)
+{
+    if (cols != chr->cols || rows != chr->rows) {
+        chr->cols = cols;
+        chr->rows = rows;
+        if (chr->be_open) {
+            qemu_chr_be_event(chr, CHR_EVENT_RESIZE);
+        }
+    }
+}
+
 QemuOpts *qemu_chr_parse_compat(const char *label, const char *filename,
                                 bool permit_mux_mon)
 {
diff --git a/include/chardev/char.h b/include/chardev/char.h
index ee9f24038b..2616c19cc0 100644
--- a/include/chardev/char.h
+++ b/include/chardev/char.h
@@ -235,6 +235,8 @@ int qemu_chr_write(Chardev *s, const uint8_t *buf, int len, bool write_all);
 #define qemu_chr_write_all(s, buf, len) qemu_chr_write(s, buf, len, true)
 int qemu_chr_wait_connected(Chardev *chr, Error **errp);
 
+void qemu_chr_resize(Chardev *chr, uint16_t cols, uint16_t rows);
+
 #define TYPE_CHARDEV "chardev"
 OBJECT_DECLARE_TYPE(Chardev, ChardevClass, CHARDEV)
 

-- 
2.56.0

[PATCH v10 04/12] char-mux: add support for the terminal size

[Filip Hejsek]

From: Szymon Lukasz <noh4hss@gmail.com>

The terminal size of a mux chardev should be the same as the real
chardev, so listen for CHR_EVENT_RESIZE to be up to date.

We forward CHR_EVENT_RESIZE only to the focused frontend. This means
frontends should update their view of the terminal size on
receiving CHR_EVENT_MUX_IN.

Signed-off-by: Szymon Lukasz <noh4hss@gmail.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Signed-off-by: Filip Hejsek <filip.hejsek@gmail.com>
---
 chardev/char-mux.c | 19 ++++++++++++++++++-
 1 file changed, 18 insertions(+), 1 deletion(-)

diff --git a/chardev/char-mux.c b/chardev/char-mux.c
index 881443d869..5a90f0221b 100644
--- a/chardev/char-mux.c
+++ b/chardev/char-mux.c
@@ -264,9 +264,24 @@ void mux_chr_send_all_event(Chardev *chr, QEMUChrEvent event)
     }
 }
 
+static void mux_update_winsize(Chardev *chr)
+{
+    MuxChardev *d = MUX_CHARDEV(chr);
+    uint16_t cols, rows;
+
+    qemu_chr_fe_get_winsize(&d->chr, &cols, &rows);
+    qemu_chr_resize(chr, cols, rows);
+}
+
 static void mux_chr_event(void *opaque, QEMUChrEvent event)
 {
-    mux_chr_send_all_event(CHARDEV(opaque), event);
+    Chardev *chr = CHARDEV(opaque);
+
+    if (event == CHR_EVENT_RESIZE) {
+        mux_update_winsize(chr);
+    } else {
+        mux_chr_send_all_event(chr, event);
+    }
 }
 
 static GSource *mux_chr_add_watch(Chardev *s, GIOCondition cond)
@@ -378,6 +393,8 @@ static bool mux_chr_open(Chardev *chr, ChardevBackend *backend, Error **errp)
         return false;
     }
 
+    mux_update_winsize(chr);
+
     /*
      * Only move to opened state if we've realized
      * the initial set of muxes:

-- 
2.56.0

[PATCH v10 05/12] main-loop: change the handling of SIGWINCH

[Filip Hejsek]

From: Szymon Lukasz <noh4hss@gmail.com>

Block SIGWINCH, so it is delivered only via signalfd.
Install a handler that uses NotifierList to tell
interested parties about SIGWINCH delivery.

Signed-off-by: Szymon Lukasz <noh4hss@gmail.com>
[Filip: add sigwinch_remove_notifier, call it in curses_cleanup]
Signed-off-by: Filip Hejsek <filip.hejsek@gmail.com>
---
 include/qemu/main-loop.h |  5 +++++
 ui/curses.c              | 21 +++++++++++++++------
 util/main-loop.c         | 33 +++++++++++++++++++++++++++++++++
 3 files changed, 53 insertions(+), 6 deletions(-)

diff --git a/include/qemu/main-loop.h b/include/qemu/main-loop.h
index 8c1241a2c1..533d4c2be4 100644
--- a/include/qemu/main-loop.h
+++ b/include/qemu/main-loop.h
@@ -449,4 +449,9 @@ typedef struct MainLoopPoll {
 void main_loop_poll_add_notifier(Notifier *notify);
 void main_loop_poll_remove_notifier(Notifier *notify);
 
+#ifndef _WIN32
+void sigwinch_add_notifier(Notifier *n);
+void sigwinch_remove_notifier(Notifier *n);
+#endif
+
 #endif
diff --git a/ui/curses.c b/ui/curses.c
index 4db32b6168..9079bfbee4 100644
--- a/ui/curses.c
+++ b/ui/curses.c
@@ -33,6 +33,7 @@
 #include <iconv.h>
 
 #include "qapi/error.h"
+#include "qemu/main-loop.h"
 #include "qemu/module.h"
 #include "ui/console.h"
 #include "ui/input.h"
@@ -149,7 +150,7 @@ static void curses_resize(DisplayChangeListener *dcl,
 }
 
 #if !defined(_WIN32) && defined(SIGWINCH) && defined(KEY_RESIZE)
-static volatile sig_atomic_t got_sigwinch;
+static bool got_sigwinch;
 static void curses_winch_check(void)
 {
     struct winsize {
@@ -172,21 +173,28 @@ static void curses_winch_check(void)
     invalidate = 1;
 }
 
-static void curses_winch_handler(int signum)
+static void curses_winch_handler(Notifier *n, void *data)
 {
     got_sigwinch = true;
 }
 
+static Notifier winch_notifier = {
+    .notify = curses_winch_handler
+};
+
 static void curses_winch_init(void)
 {
-    struct sigaction old, winch = {
-        .sa_handler  = curses_winch_handler,
-    };
-    sigaction(SIGWINCH, &winch, &old);
+    sigwinch_add_notifier(&winch_notifier);
+}
+
+static void curses_winch_cleanup(void)
+{
+    sigwinch_remove_notifier(&winch_notifier);
 }
 #else
 static void curses_winch_check(void) {}
 static void curses_winch_init(void) {}
+static void curses_winch_cleanup(void) {}
 #endif
 
 static void curses_cursor_position(DisplayChangeListener *dcl,
@@ -417,6 +425,7 @@ static void curses_cleanup(void)
         return;
     }
 
+    curses_winch_cleanup();
     endwin();
     qemu_console_unregister_listener(dcl);
     g_clear_pointer(&dcl, g_free);
diff --git a/util/main-loop.c b/util/main-loop.c
index 65e5dbcc94..e59af0e270 100644
--- a/util/main-loop.c
+++ b/util/main-loop.c
@@ -100,6 +100,7 @@ static int qemu_signal_init(Error **errp)
     sigaddset(&set, SIGIO);
     sigaddset(&set, SIGALRM);
     sigaddset(&set, SIGBUS);
+    sigaddset(&set, SIGWINCH);
     /* SIGINT cannot be handled via signalfd, so that ^C can be used
      * to interrupt QEMU when it is being run under gdb.  SIGHUP and
      * SIGTERM are also handled asynchronously, even though it is not
@@ -124,6 +125,38 @@ static int qemu_signal_init(Error **errp)
     return 0;
 }
 
+static NotifierList sigwinch_notifiers =
+    NOTIFIER_LIST_INITIALIZER(sigwinch_notifiers);
+
+static void sigwinch_handler(int signum)
+{
+    notifier_list_notify(&sigwinch_notifiers, NULL);
+}
+
+void sigwinch_add_notifier(Notifier *n)
+{
+    if (notifier_list_empty(&sigwinch_notifiers)) {
+        struct sigaction action = {
+            .sa_handler = sigwinch_handler,
+        };
+        sigaction(SIGWINCH, &action, NULL);
+    }
+
+    notifier_list_add(&sigwinch_notifiers, n);
+}
+
+void sigwinch_remove_notifier(Notifier *n)
+{
+    notifier_remove(n);
+
+    if (notifier_list_empty(&sigwinch_notifiers)) {
+        struct sigaction action = {
+            .sa_handler = SIG_DFL,
+        };
+        sigaction(SIGWINCH, &action, NULL);
+    }
+}
+
 #else /* _WIN32 */
 
 static int qemu_signal_init(Error **errp)

-- 
2.56.0

[PATCH v10 06/12] char-stdio: add support for the terminal size

[Filip Hejsek]

From: Szymon Lukasz <noh4hss@gmail.com>

Update the terminal size upon SIGWINCH delivery.

Signed-off-by: Szymon Lukasz <noh4hss@gmail.com>
[Filip: use DECLARE_INSTANCE_CHECKER,
        qemu_chr_resize_stdio -> stdio_chr_resize,
        remove notifier in char_stdio_finalize]
Signed-off-by: Filip Hejsek <filip.hejsek@gmail.com>
---
 chardev/char-stdio.c | 33 +++++++++++++++++++++++++++++++++
 1 file changed, 33 insertions(+)

diff --git a/chardev/char-stdio.c b/chardev/char-stdio.c
index fe1cbb2d88..f63bf413c7 100644
--- a/chardev/char-stdio.c
+++ b/chardev/char-stdio.c
@@ -34,7 +34,9 @@
 #include "chardev/char-win-stdio.h"
 #else
 #include <termios.h>
+#include <sys/ioctl.h>
 #include "chardev/char-fd.h"
+#include "qemu/main-loop.h"
 #endif
 
 #ifndef _WIN32
@@ -46,6 +48,14 @@ static bool stdio_in_use;
 static bool stdio_allow_signal;
 static bool stdio_echo_state;
 
+typedef struct {
+    FDChardev parent;
+    Notifier resize_notifier;
+} StdioChardev;
+
+DECLARE_INSTANCE_CHECKER(StdioChardev, STDIO_CHARDEV,
+                         TYPE_CHARDEV_STDIO)
+
 static void term_exit(void)
 {
     if (stdio_in_use) {
@@ -85,8 +95,23 @@ static void term_stdio_handler(int sig)
     stdio_chr_set_echo(NULL, stdio_echo_state);
 }
 
+static void stdio_chr_resize(Chardev *chr)
+{
+    struct winsize ws;
+    if (ioctl(1, TIOCGWINSZ, &ws) != -1) {
+        qemu_chr_resize(chr, ws.ws_col, ws.ws_row);
+    }
+}
+
+static void term_resize_notify(Notifier *n, void *data)
+{
+    StdioChardev *s = container_of(n, StdioChardev, resize_notifier);
+    stdio_chr_resize(CHARDEV(s));
+}
+
 static bool stdio_chr_open(Chardev *chr, ChardevBackend *backend, Error **errp)
 {
+    StdioChardev *s = STDIO_CHARDEV(chr);
     ChardevStdio *opts = backend->u.stdio.data;
     struct sigaction act;
 
@@ -121,6 +146,10 @@ static bool stdio_chr_open(Chardev *chr, ChardevBackend *backend, Error **errp)
     stdio_allow_signal = !opts->has_signal || opts->signal;
     stdio_chr_set_echo(chr, false);
 
+    s->resize_notifier.notify = term_resize_notify;
+    sigwinch_add_notifier(&s->resize_notifier);
+    stdio_chr_resize(chr);
+
     qemu_chr_be_event(chr, CHR_EVENT_OPENED);
     return true;
 }
@@ -152,6 +181,9 @@ static void char_stdio_class_init(ObjectClass *oc, const void *data)
 static void char_stdio_finalize(Object *obj)
 {
 #ifndef _WIN32
+    StdioChardev *s = STDIO_CHARDEV(obj);
+
+    sigwinch_remove_notifier(&s->resize_notifier);
     term_exit();
 #endif
 }
@@ -162,6 +194,7 @@ static const TypeInfo char_stdio_type_info = {
     .parent = TYPE_CHARDEV_WIN_STDIO,
 #else
     .parent = TYPE_CHARDEV_FD,
+    .instance_size = sizeof(StdioChardev),
 #endif
     .instance_finalize = char_stdio_finalize,
     .class_init = char_stdio_class_init,

-- 
2.56.0

[PATCH v10 07/12] char-win-stdio: add support for terminal size

[Filip Hejsek]

Use GetConsoleScreenBufferInfo to obtain terminal size
and set ENABLE_WINDOW_INPUT to receive resize notifications.

Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Signed-off-by: Filip Hejsek <filip.hejsek@gmail.com>
---
 chardev/char-win-stdio.c | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/chardev/char-win-stdio.c b/chardev/char-win-stdio.c
index 0deba3bffb..2132ae9a6b 100644
--- a/chardev/char-win-stdio.c
+++ b/chardev/char-win-stdio.c
@@ -44,6 +44,20 @@ typedef struct WinStdioChardev WinStdioChardev;
 DECLARE_INSTANCE_CHECKER(WinStdioChardev, WIN_STDIO_CHARDEV,
                          TYPE_CHARDEV_WIN_STDIO)
 
+static void win_stdio_chr_resize(Chardev *chr)
+{
+    HANDLE hStdOut = GetStdHandle(STD_OUTPUT_HANDLE);
+    CONSOLE_SCREEN_BUFFER_INFO ScreenBufferInfo;
+
+    if (GetConsoleScreenBufferInfo(hStdOut, &ScreenBufferInfo)) {
+        uint16_t cols = ScreenBufferInfo.srWindow.Right + 1
+                        - ScreenBufferInfo.srWindow.Left;
+        uint16_t rows = ScreenBufferInfo.srWindow.Bottom + 1
+                        - ScreenBufferInfo.srWindow.Top;
+        qemu_chr_resize(chr, cols, rows);
+    }
+}
+
 static void win_stdio_wait_func(void *opaque)
 {
     Chardev *chr = CHARDEV(opaque);
@@ -75,6 +89,9 @@ static void win_stdio_wait_func(void *opaque)
                 }
             }
         }
+        if (buf[i].EventType == WINDOW_BUFFER_SIZE_EVENT) {
+            win_stdio_chr_resize(chr);
+        }
     }
 }
 
@@ -201,6 +218,8 @@ static bool win_stdio_chr_open(Chardev *chr,
         } else {
             dwMode &= ~ENABLE_PROCESSED_INPUT;
         }
+        dwMode |= ENABLE_WINDOW_INPUT;
+        win_stdio_chr_resize(chr);
     }
 
     SetConsoleMode(stdio->hStdIn, dwMode);

-- 
2.56.0

[PATCH v10 08/12] ui/console-vc: forward text console size to vc chardev

[Filip Hejsek]

Update the vc chardev size when initializing the console and after
changing the surface image.

NOTE: There seems to be a bug in the code where the dpy_text_resize
      callback is not called when the size changes due to changing the
      surface image. (Though it doesn't cause any problem in practice
      because the callback is only used by ui/ncurses for fixed
      consoles, whose size never changes.)

Signed-off-by: Filip Hejsek <filip.hejsek@gmail.com>
---
 ui/console-vc.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/ui/console-vc.c b/ui/console-vc.c
index 53d9e9d39b..99cc8f09c8 100644
--- a/ui/console-vc.c
+++ b/ui/console-vc.c
@@ -115,12 +115,19 @@ static int vc_chr_write(Chardev *chr, const uint8_t *buf, int len)
     return vt100_input(&s->vt, buf, len);
 }
 
+static void text_console_chr_resize(QemuTextConsole *s)
+{
+    qemu_chr_resize(s->chr, s->vt.width, s->vt.height);
+}
+
 static void text_console_invalidate(void *opaque)
 {
     QemuTextConsole *s = QEMU_TEXT_CONSOLE(opaque);
 
     if (!QEMU_IS_FIXED_TEXT_CONSOLE(s)) {
         vt100_set_image(&s->vt, QEMU_CONSOLE(s)->surface->image);
+        text_console_chr_resize(s);
+        /* XXX Shouldn't qemu_text_console_update_size() also be called here? */
     }
     vt100_refresh(&s->vt);
 }
@@ -254,6 +261,7 @@ static bool vc_chr_open(Chardev *chr, ChardevBackend *backend, Error **errp)
         s->vt.t_attrib = TEXT_ATTRIBUTES_DEFAULT;
     }
 
+    text_console_chr_resize(s);
     qemu_chr_be_event(chr, CHR_EVENT_OPENED);
     qemu_console_notify(QEMU_CONSOLE_ADDED, QEMU_CONSOLE(s));
     return true;

-- 
2.56.0

[PATCH v10 09/12] ui/gtk: forward gtk console size to vc chardev

[Filip Hejsek]

Query the terminal size from the vte library when creating the console
and every time it might change. Vte doesn't send any signal specifically
for terminal size changes, so instead we register callbacks for
size-allocate and char-size-changed.

Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Signed-off-by: Filip Hejsek <filip.hejsek@gmail.com>
---
 ui/gtk.c | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/ui/gtk.c b/ui/gtk.c
index ed7ffc06b1..8d312d6a4b 100644
--- a/ui/gtk.c
+++ b/ui/gtk.c
@@ -2196,6 +2196,28 @@ static gboolean gd_vc_in(VteTerminal *terminal, gchar *text, guint size,
     return TRUE;
 }
 
+static void gd_vc_vte_update_size(VirtualConsole *vc)
+{
+    uint16_t cols, rows;
+    cols = vte_terminal_get_column_count(VTE_TERMINAL(vc->vte.terminal));
+    rows = vte_terminal_get_row_count(VTE_TERMINAL(vc->vte.terminal));
+    qemu_chr_resize(vc->vte.chr, cols, rows);
+}
+
+static void gd_vc_size_allocate(VteTerminal *terminal,
+                                GtkAllocation *allocation, gpointer user_data)
+{
+    VirtualConsole *vc = user_data;
+    gd_vc_vte_update_size(vc);
+}
+
+static void gd_vc_char_size_changed(VteTerminal *terminal, guint width,
+                                    guint height, gpointer user_data)
+{
+    VirtualConsole *vc = user_data;
+    gd_vc_vte_update_size(vc);
+}
+
 static void gd_vc_vte_init(GtkDisplayState *s, VirtualConsole *vc,
                            Chardev *chr, int idx)
 {
@@ -2258,6 +2280,12 @@ static void gd_vc_vte_init(GtkDisplayState *s, VirtualConsole *vc,
                              gtk_label_new(vc->label));
 
     qemu_chr_be_event(vc->vte.chr, CHR_EVENT_OPENED);
+
+    g_signal_connect(vc->vte.terminal, "size-allocate",
+                     G_CALLBACK(gd_vc_size_allocate), vc);
+    g_signal_connect(vc->vte.terminal, "char-size-changed",
+                     G_CALLBACK(gd_vc_char_size_changed), vc);
+    gd_vc_vte_update_size(vc);
 }
 
 static void gd_vcs_init(GtkDisplayState *s)

-- 
2.56.0

[PATCH v10 10/12] qmp: add chardev-window-size-changed command

[Filip Hejsek]

From: Szymon Lukasz <noh4hss@gmail.com>

The management software can use this command to notify QEMU about the
size of the terminal connected to a chardev, QEMU can then forward this
information to the guest if the chardev is connected to a virtio console
device.

Signed-off-by: Szymon Lukasz <noh4hss@gmail.com>
Suggested-by: Daniel P. Berrangé <berrange@redhat.com>
[Filip: rename command, change documentation]
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Acked-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Filip Hejsek <filip.hejsek@gmail.com>
---
 chardev/char.c | 14 ++++++++++++++
 qapi/char.json | 31 +++++++++++++++++++++++++++++++
 2 files changed, 45 insertions(+)

diff --git a/chardev/char.c b/chardev/char.c
index 8c8386e5b5..fe513ae962 100644
--- a/chardev/char.c
+++ b/chardev/char.c
@@ -1347,6 +1347,20 @@ bool qmp_add_client_char(int fd, bool has_skipauth, bool skipauth,
     return true;
 }
 
+void qmp_chardev_window_size_changed(const char *id, uint16_t cols,
+                                     uint16_t rows, Error **errp)
+{
+    Chardev *chr;
+
+    chr = qemu_chr_find(id);
+    if (chr == NULL) {
+        error_setg(errp, "Chardev '%s' not found", id);
+        return;
+    }
+
+    qemu_chr_resize(chr, cols, rows);
+}
+
 /*
  * Add a timeout callback for the chardev (in milliseconds), return
  * the GSource object created. Please use this to add timeout hook for
diff --git a/qapi/char.json b/qapi/char.json
index 7ae67eedff..842e003194 100644
--- a/qapi/char.json
+++ b/qapi/char.json
@@ -862,6 +862,37 @@
 { 'command': 'chardev-send-break',
   'data': { 'id': 'str' } }
 
+##
+# @chardev-window-size-changed:
+#
+# Notifies a chardev about the current size of the terminal connected
+# to this chardev.  The information will be forwarded to the guest if
+# the chardev is connected to a virtio console device.
+#
+# The initial size is 0x0, which should be interpreted as an unknown
+# size.
+#
+# Some backends detect the terminal size automatically, in which case
+# the size may unpredictably revert to the detected one at any time.
+#
+# @id: the chardev's ID
+#
+# @cols: the number of columns
+#
+# @rows: the number of rows
+#
+# Since: 11.2
+#
+# .. qmp-example::
+#
+#     -> { "execute": "chardev-window-size-changed", "arguments": { "id": "foo", "cols": 80, "rows": 24 } }
+#     <- { "return": {} }
+##
+{ 'command': 'chardev-window-size-changed',
+  'data': { 'id': 'str',
+            'cols': 'uint16',
+            'rows': 'uint16' } }
+
 ##
 # @VSERPORT_CHANGE:
 #     Emitted when the guest opens or closes a virtio-serial port.

-- 
2.56.0

[PATCH v10 11/12] virtio-serial-bus: add terminal resize messages

[Filip Hejsek]

Implement the part of the virtio spec that allows to notify the virtio
driver about terminal resizes. Gate the new resize support behind the
console-size property, which defaults to off. To implement the property,
restore VirtIOSerial::host_features (previously removed by commit
d0660e5b7fc7e97926232d13d2500a16df32b310).

The virtio spec contains two methods to inform the guest about console
size:

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. Unfortunately, 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 running an
old guest kernel, the number of rows and columns will be swapped.

Based on a patch originally written by Szymon Lukasz <noh4hss@gmail.com>,
but partially rewritten to fix various corner cases.

Signed-off-by: Szymon Lukasz <noh4hss@gmail.com>
Signed-off-by: Filip Hejsek <filip.hejsek@gmail.com>
---
 hw/char/trace-events              |  1 +
 hw/char/virtio-serial-bus.c       | 81 ++++++++++++++++++++++++++++++++++++++-
 include/hw/virtio/virtio-serial.h |  7 ++++
 3 files changed, 87 insertions(+), 2 deletions(-)

diff --git a/hw/char/trace-events b/hw/char/trace-events
index a3fcc77287..e387c8853f 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 c36e18a4cf..882765ac88 100644
--- a/hw/char/virtio-serial-bus.c
+++ b/hw/char/virtio-serial-bus.c
@@ -261,6 +261,68 @@ 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;
+};
+
+static void send_console_resize(VirtIOSerialPort *port)
+{
+    VirtIOSerial *vser = port->vser;
+    VirtIODevice *vdev = VIRTIO_DEVICE(vser);
+
+    if (!virtio_has_feature(vser->host_features, VIRTIO_CONSOLE_F_SIZE)) {
+        return;
+    }
+
+    trace_virtio_serial_send_console_resize(port->id, port->cols, port->rows);
+
+    if (use_multiport(vser)) {
+        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, port->cols);
+        virtio_stw_p(vdev, &buffer.resize.rows, port->rows);
+
+        send_control_msg(vser, &buffer, sizeof(buffer));
+    }
+}
+
+void virtio_serial_resize_console(VirtIOSerialPort *port,
+                                  uint16_t cols, uint16_t rows)
+{
+    VirtIOSerial *vser = port->vser;
+    VirtIODevice *vdev = VIRTIO_DEVICE(vser);
+
+    if (port->cols == cols && port->rows == rows) {
+        return;
+    }
+
+    port->cols = cols;
+    port->rows = rows;
+
+    if (port->id == 0 && !use_multiport(vser) &&
+        virtio_vdev_has_feature(vdev, VIRTIO_CONSOLE_F_SIZE)) {
+        virtio_notify_config(vdev);
+    }
+
+    /*
+     * We will send these messages even before we told the guest that
+     * it is a console port (by sending VIRTIO_CONSOLE_CONSOLE_PORT
+     * message), but that should be fine as the guest will likely
+     * ignore them.
+     */
+    send_console_resize(port);
+}
+
 /* Functions for use inside qemu to open and read from/write to ports */
 int virtio_serial_open(VirtIOSerialPort *port)
 {
@@ -403,6 +465,7 @@ static void handle_control_message(VirtIOSerial *vser,
          */
         if (vsc->is_console) {
             send_control_event(vser, port->id, VIRTIO_CONSOLE_CONSOLE_PORT, 1);
+            send_console_resize(port);
         }
 
         if (port->name) {
@@ -538,6 +601,7 @@ static uint64_t get_features(VirtIODevice *vdev, uint64_t features,
 
     vser = VIRTIO_SERIAL(vdev);
 
+    features |= vser->host_features;
     features |= BIT_ULL(VIRTIO_CONSOLE_F_EMERG_WRITE);
     if (vser->bus.max_nr_ports > 1) {
         virtio_add_feature(&features, VIRTIO_CONSOLE_F_MULTIPORT);
@@ -549,11 +613,18 @@ static uint64_t get_features(VirtIODevice *vdev, uint64_t features,
 static void get_config(VirtIODevice *vdev, uint8_t *config_data)
 {
     VirtIOSerial *vser = VIRTIO_SERIAL(vdev);
+    VirtIOSerialPort *port;
     struct virtio_console_config *config =
         (struct virtio_console_config *)config_data;
 
-    config->cols = 0;
-    config->rows = 0;
+    port = find_port_by_id(vser, 0);
+    if (port) {
+        config->cols = virtio_tswap16(vdev, port->cols);
+        config->rows = virtio_tswap16(vdev, port->rows);
+    } else {
+        config->cols = 0;
+        config->rows = 0;
+    }
     config->max_nr_ports = virtio_tswap32(vdev,
                                           vser->serial.max_virtserial_ports);
 }
@@ -716,6 +787,10 @@ static void virtio_serial_post_load_timer_cb(void *opaque)
                                port->host_connected);
         }
         vsc = VIRTIO_SERIAL_PORT_GET_CLASS(port);
+        /*
+         * TODO: let the guest know about new console size if it has changed
+         * (this will require sending old size in the migration stream)
+         */
         if (vsc->set_guest_connected) {
             vsc->set_guest_connected(port, port->guest_connected);
         }
@@ -1142,6 +1217,8 @@ static const VMStateDescription vmstate_virtio_console = {
 static const Property virtio_serial_properties[] = {
     DEFINE_PROP_UINT32("max_ports", VirtIOSerial, serial.max_virtserial_ports,
                                                   31),
+    DEFINE_PROP_BIT64("console-size", VirtIOSerial, host_features,
+                      VIRTIO_CONSOLE_F_SIZE, false),
 };
 
 static void virtio_serial_class_init(ObjectClass *klass, const void *data)
diff --git a/include/hw/virtio/virtio-serial.h b/include/hw/virtio/virtio-serial.h
index da0c91e1a4..bda6d5312a 100644
--- a/include/hw/virtio/virtio-serial.h
+++ b/include/hw/virtio/virtio-serial.h
@@ -145,6 +145,9 @@ struct VirtIOSerialPort {
     bool host_connected;
     /* Do apps not want to receive data? */
     bool throttled;
+
+    /* Terminal size reported to the guest.  Only used for consoles. */
+    uint16_t cols, rows;
 };
 
 /* The virtio-serial bus on top of which the ports will ride as devices */
@@ -186,6 +189,8 @@ struct VirtIOSerial {
     struct VirtIOSerialPostLoad *post_load;
 
     virtio_serial_conf serial;
+
+    uint64_t host_features;
 };
 
 /* Interface to the virtio-serial bus */
@@ -220,5 +225,7 @@ size_t virtio_serial_guest_ready(VirtIOSerialPort *port);
  */
 void virtio_serial_throttle_port(VirtIOSerialPort *port, bool throttle);
 
+void virtio_serial_resize_console(VirtIOSerialPort *port,
+                                  uint16_t cols, uint16_t rows);
 
 #endif

-- 
2.56.0

[PATCH v10 12/12] virtio-console: notify the guest about terminal resizes

[Filip Hejsek]

From: Szymon Lukasz <noh4hss@gmail.com>

If a virtio serial port is a console port, forward terminal resize
messages from the chardev backend to the guest.

Signed-off-by: Szymon Lukasz <noh4hss@gmail.com>
[Filip: rename things, remove logic that is now handled in virtio-serial-bus.c]
Signed-off-by: Filip Hejsek <filip.hejsek@gmail.com>
---
 hw/char/virtio-console.c | 34 +++++++++++++++++++++++++++++++---
 1 file changed, 31 insertions(+), 3 deletions(-)

diff --git a/hw/char/virtio-console.c b/hw/char/virtio-console.c
index 36ad2ddc3f..db9d8ca797 100644
--- a/hw/char/virtio-console.c
+++ b/hw/char/virtio-console.c
@@ -107,6 +107,15 @@ static ssize_t flush_buf(VirtIOSerialPort *port,
     return ret;
 }
 
+static void virtconsole_update_size(VirtIOSerialPort *port)
+{
+    uint16_t cols, rows;
+    VirtConsole *vcon = VIRTIO_CONSOLE(port);
+
+    qemu_chr_fe_get_winsize(&vcon->chr, &cols, &rows);
+    virtio_serial_resize_console(port, cols, rows);
+}
+
 /* Callback function that's called when the guest opens/closes the port */
 static void set_guest_connected(VirtIOSerialPort *port, int guest_connected)
 {
@@ -171,6 +180,23 @@ static void chr_event(void *opaque, QEMUChrEvent event)
     }
 }
 
+static void chr_event_console(void *opaque, QEMUChrEvent event)
+{
+    VirtConsole *vcon = opaque;
+    VirtIOSerialPort *port = VIRTIO_SERIAL_PORT(vcon);
+
+    trace_virtio_console_chr_event(port->id, event);
+    switch (event) {
+    case CHR_EVENT_OPENED:
+    case CHR_EVENT_MUX_IN:
+    case CHR_EVENT_RESIZE:
+        virtconsole_update_size(port);
+        break;
+    default:
+        break;
+    }
+}
+
 static int chr_be_change(void *opaque)
 {
     VirtConsole *vcon = opaque;
@@ -179,7 +205,9 @@ static int chr_be_change(void *opaque)
 
     if (k->is_console) {
         qemu_chr_fe_set_handlers(&vcon->chr, chr_can_read, chr_read,
-                                 NULL, chr_be_change, vcon, NULL, true);
+                                 chr_event_console, chr_be_change,
+                                 vcon, NULL, true);
+        virtconsole_update_size(port);
     } else {
         qemu_chr_fe_set_handlers(&vcon->chr, chr_can_read, chr_read,
                                  chr_event, chr_be_change, vcon, NULL, false);
@@ -207,7 +235,7 @@ static void virtconsole_enable_backend(VirtIOSerialPort *port, bool enable)
         VirtIOSerialPortClass *k = VIRTIO_SERIAL_PORT_GET_CLASS(port);
 
         qemu_chr_fe_set_handlers(&vcon->chr, chr_can_read, chr_read,
-                                 k->is_console ? NULL : chr_event,
+                                 k->is_console ? chr_event_console : chr_event,
                                  chr_be_change, vcon, NULL, false);
     } else {
         qemu_chr_fe_set_handlers(&vcon->chr, NULL, NULL, NULL,
@@ -239,7 +267,7 @@ static void virtconsole_realize(DeviceState *dev, Error **errp)
          */
         if (k->is_console) {
             qemu_chr_fe_set_handlers(&vcon->chr, chr_can_read, chr_read,
-                                     NULL, chr_be_change,
+                                     chr_event_console, chr_be_change,
                                      vcon, NULL, true);
             virtio_serial_open(port);
         } else {

-- 
2.56.0

Re: [PATCH v10 00/12] virtio-console: notify about the terminal size

[Michael S. Tsirkin]

On Mon, Oct 12, 2026 at 04:04:59PM +0200, Filip Hejsek wrote:
> Summary of the Series
> ---------------------
> 
> This series adds terminal size support to the virtio-console device.
> The goal is to make it possible to get a resizable terminal into a guest
> without using e.g. ssh.
> 
> Support for detecting terminal size is added to stdio and vc backends,
> but not pty and serial, because for the later it's unfortunately
> impossible to get resize notifications.
> 
> A QMP command is added for notifying QEMU about the terminal size
> of any chardev. This can be used by clients to support resizing for
> devices where QEMU is not able to detect the size by itself (e.g. virsh
> console).
> 
> There was a bug in Linux versions prior to 6.15 which caused the
> dimensions to be interpreted incorrectly by the guest. The fix has
> been backported to currently supported kernels, but to avoid making the
> terminal harder to use on out of date guests, the feature is disabled
> by default and must be enabled with the console-size property.
> 
> Limitations
> -----------
> 
> There is no documentation for the virtio-serial device. I'm working on
> this and will submit it separately.
> 
> Resizing support for the spice version of 'vc' chardev is still missing.
> 
> After migration, the guest is not informed about the new console size.
> I propably won't fix this any time soon unless someone helps me with
> migration stream changes.

virtio things:

Acked-by: Michael S. Tsirkin <mst@redhat.com>

> Full Changelog
> --------------
> 
> v10:
> - Fix build error on win32
> - Link to v9: https://lore.kernel.org/qemu-devel/20261012-console-resize-v9-0-8db78320ba81@gmail.com
> 
> v9:
> - Clean up SIGWINCH notifier when stdio or curses chardev is destroyed
> - Link to v8: https://lore.kernel.org/qemu-devel/20260929-console-resize-v8-0-2ff9183f8750@gmail.com
> 
> v8:
> - Rebased
> - Fixed uninitialized buffer in send_console_resize
> - "Since: 11.1" -> "Since: 11.2"
> - Link to v7: https://lore.kernel.org/qemu-devel/20260609-console-resize-v7-0-0c550fdcec15@gmail.com
> 
> v7:
> - Rebased
> - Renamed some functions
> - Made virtio size support disabled by default
> - "Since: 11.0" -> "Since: 11.1"
> - Dropped "must exist" from chardev id param description in qmp docs
> - Link to v6: https://lore.kernel.org/qemu-devel/20260119-console-resize-v6-0-33a7b0330a7a@gmail.com
> 
> v6:
> - Rebased (renaming CharBackend -> CharFrontend)
> - Virtio resize message code rewritten to fix corner cases
> - Updated version numbers ('Since: 11.0', hw_compat_10_2)
> - Added note to CHR_EVENT_RESIZE definition comment, explaining
>   that only the focused frontend gets the event
> - Fixed checkpatch warning (line length)
> - Link to v5: https://lore.kernel.org/qemu-devel/20250921-console-resize-v5-0-89e3c6727060@gmail.com
> 
> v5:
> - Rename chardev-resize -> chardev-window-size-changed
> - Improve chardev-window-size-changed documentation
> - Add partial implementation for 'vc' chardev
> - Config space now returns port 0 size if multiport
> - Console-size property completely disables size support
> - Fix misnamed variables in char-win-stdio
> - Link to v4: https://lore.kernel.org/qemu-devel/20250912-console-resize-v4-0-7925e444afc4@gmail.com
> 
> v4:
> - Changed order of rows and cols fields
> - Added support for terminal size on Windows
> - Trace event is also emitted for legacy (non-multiport) drivers
> - Minor fixes required because of changes in QEMU (DECLARE_INSTANCE_CHECKER, qmp-example)
> - Updated version numbers ('Since: 10.2', hw_compat_10_1)
> - Link to v3: https://lore.kernel.org/qemu-devel/20200629164041.472528-1-noh4hss@gmail.com
> 
> v3:
> - Add resize messages over QMP, as suggested by Daniel
> 
> v2:
> - Fix adding a new virtio feature bit to the virtio console device
> 
> ---
> Filip Hejsek (4):
>       char-win-stdio: add support for terminal size
>       ui/console-vc: forward text console size to vc chardev
>       ui/gtk: forward gtk console size to vc chardev
>       virtio-serial-bus: add terminal resize messages
> 
> Szymon Lukasz (8):
>       chardev: add cols, rows fields
>       chardev: add CHR_EVENT_RESIZE
>       chardev: add qemu_chr_resize()
>       char-mux: add support for the terminal size
>       main-loop: change the handling of SIGWINCH
>       char-stdio: add support for the terminal size
>       qmp: add chardev-window-size-changed command
>       virtio-console: notify the guest about terminal resizes
> 
>  backends/cryptodev-vhost-user.c   |  1 +
>  chardev/char-fe.c                 | 13 +++++++
>  chardev/char-mux.c                | 19 ++++++++-
>  chardev/char-stdio.c              | 33 ++++++++++++++++
>  chardev/char-win-stdio.c          | 19 +++++++++
>  chardev/char.c                    | 26 +++++++++++++
>  hw/block/vhost-user-blk.c         |  1 +
>  hw/char/terminal3270.c            |  1 +
>  hw/char/trace-events              |  1 +
>  hw/char/virtio-console.c          | 35 +++++++++++++++--
>  hw/char/virtio-serial-bus.c       | 81 ++++++++++++++++++++++++++++++++++++++-
>  hw/display/vhost-user-media.c     |  1 +
>  hw/ipmi/ipmi_bmc_extern.c         |  1 +
>  hw/scsi/vhost-user-scsi.c         |  1 +
>  hw/usb/ccid-card-passthru.c       |  1 +
>  hw/usb/dev-serial.c               |  1 +
>  hw/usb/redirect.c                 |  1 +
>  hw/virtio/vhost-user-base.c       |  1 +
>  hw/virtio/vhost-user-scmi.c       |  1 +
>  include/chardev/char-fe.h         | 10 +++++
>  include/chardev/char.h            |  9 +++++
>  include/hw/virtio/virtio-serial.h |  7 ++++
>  include/qemu/main-loop.h          |  5 +++
>  monitor/hmp.c                     |  1 +
>  monitor/qmp.c                     |  1 +
>  net/passt.c                       |  1 +
>  net/vhost-user.c                  |  1 +
>  qapi/char.json                    | 31 +++++++++++++++
>  ui/console-vc.c                   |  8 ++++
>  ui/curses.c                       | 21 +++++++---
>  ui/gtk.c                          | 28 ++++++++++++++
>  util/main-loop.c                  | 33 ++++++++++++++++
>  32 files changed, 382 insertions(+), 12 deletions(-)
> ---
> base-commit: 615ece3c406b262996e569f29ea6eed0d81c4d8d
> change-id: 20250912-console-resize-96c42140ba08
> 
> Best regards,
> --  
> Filip Hejsek <filip.hejsek@gmail.com>