[v4] virtio-console: notify about the terminal size

[PATCH v4 00/10] virtio-console: notify about the terminal size

Posted by Filip Hejsek 2 weeks, 2 days ago

The goal of this series is to have a resizable terminal into a guest
without having to set up networking and using, e.g. ssh.

The virtio spec allows a virtio-console device to notify the guest about
terminal resizes in the host. Linux Kernel implements the driver part of
the spec. This series implement the device part in QEMU.

This series adds support for a resizable terminal if a virtio console
device is connected to the stdio backend.

This series also introduces resize messages that can be sent over QMP to
notify QEMU about the size of the terminal connented to some chardev.
In the libvirt setting, it will allow to implement a resizable terminal
for virsh console and other libvirt clients.

This patch series was originally authored by Szymon Lukasz and submitted
to qemu-devel about 5 years ago. The previous submission can be found at
<https://lists.nongnu.org/archive/html/qemu-devel/2020-06/msg09591.html>.
I have updated the patches to be compatible with latest master and made
a few small changes of my own, including the addition of Windows support.

Probably the most important change I made is the swapping of rows and
cols fields in resize messages. I would like to hear some feedback on
this change from reviewers. The problem is that for a long time, the
Linux kernel used a different field order from what was specified in the
virtio spec. The kernel implementation was apparently merged around 2010,
while the virtio spec came in 2014, so when a previous version of this
patch series was being discussed here on this mailing list in 2020, it
was decided that QEMU should match the Linux implementation, and ideally,
the virtio spec should be changed.

However, recently, the Linux kernel implementation was changed to conform
to the spec: <https://git.kernel.org/linus/5326ab737a47278dbd16ed3ee7380b26c7056ddd>.
As a result, to be compatible with latest kernel releases, QEMU needs to
also use the field order matching the specification. I have changed the
patch to use the spec-compliant order, so it works correctly with latest
kernels now.

That leaves the issue of older kernels. There are about 15 years' worth
of kernel versions with the swapped field order, including the kernel
currently shipped in Debian stable. The effects of the swapped dimensions
can sometimes be quite annoying - e.g. if you have a terminal with
24 rows, this will be interpreted as 24 columns, and your shell may limit 
line editing to this small space, most of which will be taken by your
prompt. The patch series in its current form provides no way to disable
the console size functionality, so users may end up worse off than if
the functionality were not implemented at all.

PS: One of the patches adds one additional noop switch case
    to a bunch of files. I didn't include the maintainers of these files
    in the Cc list. I hope that's OK. :)

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)

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 (1):
      char-win-stdio: add support for terminal size

Szymon Lukasz (9):
      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-resize command
      virtio-serial-bus: add terminal resize messages
      virtio-console: notify the guest about terminal resizes

 backends/cryptodev-vhost-user.c   |  1 +
 chardev/char-fe.c                 | 13 ++++++++
 chardev/char-mux.c                | 18 ++++++++++-
 chardev/char-stdio.c              | 30 +++++++++++++++++++
 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          | 63 ++++++++++++++++++++++++++++++++++++---
 hw/char/virtio-serial-bus.c       | 43 ++++++++++++++++++++++++--
 hw/core/machine.c                 |  4 ++-
 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            |  7 +++++
 include/hw/virtio/virtio-serial.h |  5 ++++
 include/qemu/main-loop.h          |  4 +++
 monitor/hmp.c                     |  1 +
 monitor/qmp.c                     |  1 +
 net/passt.c                       |  1 +
 net/vhost-user.c                  |  1 +
 qapi/char.json                    | 22 ++++++++++++++
 ui/curses.c                       | 11 +++----
 util/main-loop.c                  | 21 +++++++++++++
 30 files changed, 298 insertions(+), 13 deletions(-)
---
base-commit: 190d5d7fd725ff754f94e8e0cbfb69f279c82b5d
change-id: 20250912-console-resize-96c42140ba08

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

Re: [PATCH v4 00/10] virtio-console: notify about the terminal size

Posted by Filip Hejsek 1 week, 5 days ago

While thinking about the patches, a few questions about the virtio spec
have popped into my head.

1. Should the config space size also be updated (for port 0) when
multiport is used? Based on my reading of the spec, I think yes.

2. Can VIRTIO_CONSOLE_RESIZE be sent if VIRTIO_CONSOLE_F_SIZE is not
negotiated? The spec does not say, which I think means it can.

3. The spec says that reading from config space fields that are
conditional on features should be allowed even if the driver has not
(yet) accepted the feature. Does it mean that we have to update the
size even if the feature is not accepted (yet), or is it OK if the
reads return 0?

Thanks for any answers or opinions,
Filip Hejsek

Re: [PATCH v4 00/10] virtio-console: notify about the terminal size

Posted by Michael S. Tsirkin 1 week, 5 days ago

On Tue, Sep 16, 2025 at 01:02:02AM +0200, Filip Hejsek wrote:
> While thinking about the patches, a few questions about the virtio spec
> have popped into my head.
> 
> 1. Should the config space size also be updated (for port 0) when
> multiport is used? Based on my reading of the spec, I think yes.
> 
> 2. Can VIRTIO_CONSOLE_RESIZE be sent if VIRTIO_CONSOLE_F_SIZE is not
> negotiated? The spec does not say, which I think means it can.

But the guest can't do anything useful here.

> 3. The spec says that reading from config space fields that are
> conditional on features should be allowed even if the driver has not
> (yet) accepted the feature. Does it mean that we have to update the
> size even if the feature is not accepted (yet), or is it OK if the
> reads return 0?

This is talking about the window before FEATURES_OK (and so DRIVER_OK)
is set.  It is best to update the size. There's no interrupt to send
though.


> Thanks for any answers or opinions,
> Filip Hejsek

Re: [PATCH v4 00/10] virtio-console: notify about the terminal size

Posted by Michael S. Tsirkin 2 weeks, 2 days ago

On Fri, Sep 12, 2025 at 05:39:45AM +0200, Filip Hejsek wrote:
> The goal of this series is to have a resizable terminal into a guest
> without having to set up networking and using, e.g. ssh.
> 
> The virtio spec allows a virtio-console device to notify the guest about
> terminal resizes in the host. Linux Kernel implements the driver part of
> the spec. This series implement the device part in QEMU.
> 
> This series adds support for a resizable terminal if a virtio console
> device is connected to the stdio backend.
> 
> This series also introduces resize messages that can be sent over QMP to
> notify QEMU about the size of the terminal connented to some chardev.
> In the libvirt setting, it will allow to implement a resizable terminal
> for virsh console and other libvirt clients.
> 
> This patch series was originally authored by Szymon Lukasz and submitted
> to qemu-devel about 5 years ago. The previous submission can be found at
> <https://lists.nongnu.org/archive/html/qemu-devel/2020-06/msg09591.html>.
> I have updated the patches to be compatible with latest master and made
> a few small changes of my own, including the addition of Windows support.
> 
> Probably the most important change I made is the swapping of rows and
> cols fields in resize messages. I would like to hear some feedback on
> this change from reviewers. The problem is that for a long time, the
> Linux kernel used a different field order from what was specified in the
> virtio spec. The kernel implementation was apparently merged around 2010,
> while the virtio spec came in 2014, so when a previous version of this
> patch series was being discussed here on this mailing list in 2020, it
> was decided that QEMU should match the Linux implementation, and ideally,
> the virtio spec should be changed.
> 
> However, recently, the Linux kernel implementation was changed to conform
> to the spec: <https://git.kernel.org/linus/5326ab737a47278dbd16ed3ee7380b26c7056ddd>.
> As a result, to be compatible with latest kernel releases, QEMU needs to
> also use the field order matching the specification. I have changed the
> patch to use the spec-compliant order, so it works correctly with latest
> kernels now.
>

Well this is not in any release yet. If you want me to revert that
one, let me know ASAP. Maximilian?

> That leaves the issue of older kernels. There are about 15 years' worth
> of kernel versions with the swapped field order, including the kernel
> currently shipped in Debian stable. The effects of the swapped dimensions
> can sometimes be quite annoying - e.g. if you have a terminal with
> 24 rows, this will be interpreted as 24 columns, and your shell may limit 
> line editing to this small space, most of which will be taken by your
> prompt. The patch series in its current form provides no way to disable
> the console size functionality,

Well I see the console-size property, no?

> so users may end up worse off than if
> the functionality were not implemented at all.

If we want to keep the Linux patch, the straight forward way is to send
the fix to stable@ then poke at Debian at al to fix their kernels.

Another option is to make the property default to off, have
management turn it on when guest is up to date.

But it really sounds like we should revert that Linux patch.
I posted a revert, pls comment.

> PS: One of the patches adds one additional noop switch case
>     to a bunch of files. I didn't include the maintainers of these files
>     in the Cc list. I hope that's OK. :)
> 
> 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)
> 
> 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 (1):
>       char-win-stdio: add support for terminal size
> 
> Szymon Lukasz (9):
>       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-resize command
>       virtio-serial-bus: add terminal resize messages
>       virtio-console: notify the guest about terminal resizes
> 
>  backends/cryptodev-vhost-user.c   |  1 +
>  chardev/char-fe.c                 | 13 ++++++++
>  chardev/char-mux.c                | 18 ++++++++++-
>  chardev/char-stdio.c              | 30 +++++++++++++++++++
>  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          | 63 ++++++++++++++++++++++++++++++++++++---
>  hw/char/virtio-serial-bus.c       | 43 ++++++++++++++++++++++++--
>  hw/core/machine.c                 |  4 ++-
>  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            |  7 +++++
>  include/hw/virtio/virtio-serial.h |  5 ++++
>  include/qemu/main-loop.h          |  4 +++
>  monitor/hmp.c                     |  1 +
>  monitor/qmp.c                     |  1 +
>  net/passt.c                       |  1 +
>  net/vhost-user.c                  |  1 +
>  qapi/char.json                    | 22 ++++++++++++++
>  ui/curses.c                       | 11 +++----
>  util/main-loop.c                  | 21 +++++++++++++
>  30 files changed, 298 insertions(+), 13 deletions(-)
> ---
> base-commit: 190d5d7fd725ff754f94e8e0cbfb69f279c82b5d
> change-id: 20250912-console-resize-96c42140ba08
> 
> Best regards,
> -- 
> Filip Hejsek <filip.hejsek@gmail.com>

Re: [PATCH v4 00/10] virtio-console: notify about the terminal size

Posted by Daniel P. Berrangé 2 weeks, 2 days ago

On Fri, Sep 12, 2025 at 04:41:02AM -0400, Michael S. Tsirkin wrote:
> On Fri, Sep 12, 2025 at 05:39:45AM +0200, Filip Hejsek wrote:
> > The goal of this series is to have a resizable terminal into a guest
> > without having to set up networking and using, e.g. ssh.
> > 
> > The virtio spec allows a virtio-console device to notify the guest about
> > terminal resizes in the host. Linux Kernel implements the driver part of
> > the spec. This series implement the device part in QEMU.
> > 
> > This series adds support for a resizable terminal if a virtio console
> > device is connected to the stdio backend.
> > 
> > This series also introduces resize messages that can be sent over QMP to
> > notify QEMU about the size of the terminal connented to some chardev.
> > In the libvirt setting, it will allow to implement a resizable terminal
> > for virsh console and other libvirt clients.
> > 
> > This patch series was originally authored by Szymon Lukasz and submitted
> > to qemu-devel about 5 years ago. The previous submission can be found at
> > <https://lists.nongnu.org/archive/html/qemu-devel/2020-06/msg09591.html>.
> > I have updated the patches to be compatible with latest master and made
> > a few small changes of my own, including the addition of Windows support.
> > 
> > Probably the most important change I made is the swapping of rows and
> > cols fields in resize messages. I would like to hear some feedback on
> > this change from reviewers. The problem is that for a long time, the
> > Linux kernel used a different field order from what was specified in the
> > virtio spec. The kernel implementation was apparently merged around 2010,
> > while the virtio spec came in 2014, so when a previous version of this
> > patch series was being discussed here on this mailing list in 2020, it
> > was decided that QEMU should match the Linux implementation, and ideally,
> > the virtio spec should be changed.
> > 
> > However, recently, the Linux kernel implementation was changed to conform
> > to the spec: <https://git.kernel.org/linus/5326ab737a47278dbd16ed3ee7380b26c7056ddd>.
> > As a result, to be compatible with latest kernel releases, QEMU needs to
> > also use the field order matching the specification. I have changed the
> > patch to use the spec-compliant order, so it works correctly with latest
> > kernels now.
> >
> 
> Well this is not in any release yet. If you want me to revert that
> one, let me know ASAP. Maximilian?
> 
> > That leaves the issue of older kernels. There are about 15 years' worth
> > of kernel versions with the swapped field order, including the kernel
> > currently shipped in Debian stable. The effects of the swapped dimensions
> > can sometimes be quite annoying - e.g. if you have a terminal with
> > 24 rows, this will be interpreted as 24 columns, and your shell may limit 
> > line editing to this small space, most of which will be taken by your
> > prompt. The patch series in its current form provides no way to disable
> > the console size functionality,
> 
> Well I see the console-size property, no?

At least in the case of libvirt managed VMs, this series does
nothin by default, as they won't be using the 'stdio' chardev,
they'll require libvirt to first wire up the new QMP command,
and then apps using libvirt to call it. So in that sense, it'll
take a while before the effects are seen by users.

> > so users may end up worse off than if
> > the functionality were not implemented at all.
> 
> If we want to keep the Linux patch, the straight forward way is to send
> the fix to stable@ then poke at Debian at al to fix their kernels.
> 
> Another option is to make the property default to off, have
> management turn it on when guest is up to date.
> 
> But it really sounds like we should revert that Linux patch.
> I posted a revert, pls comment.

What about other non-Linux guest OS that may have correctly
implemented the virtio spec ?

At least FreeBSD appears to /not/ implemenmt resize at all:

  https://github.com/freebsd/freebsd-src/blob/main/sys/dev/virtio/console/virtio_console.c#L884

Do we have a Windows impl of virtio-console with resize support ?

Any other places we should check ?

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 :|

Re: [PATCH v4 00/10] virtio-console: notify about the terminal size

Posted by Maximilian Immanuel Brandtner 1 week, 6 days ago

On Fri, 2025-09-12 at 09:50 +0100, Daniel P. Berrangé wrote:
> On Fri, Sep 12, 2025 at 04:41:02AM -0400, Michael S. Tsirkin wrote:
> > On Fri, Sep 12, 2025 at 05:39:45AM +0200, Filip Hejsek wrote:
> > > The goal of this series is to have a resizable terminal into a
> > > guest
> > > without having to set up networking and using, e.g. ssh.
> > > 
> > > The virtio spec allows a virtio-console device to notify the
> > > guest about
> > > terminal resizes in the host. Linux Kernel implements the driver
> > > part of
> > > the spec. This series implement the device part in QEMU.
> > > 
> > > This series adds support for a resizable terminal if a virtio
> > > console
> > > device is connected to the stdio backend.
> > > 
> > > This series also introduces resize messages that can be sent over
> > > QMP to
> > > notify QEMU about the size of the terminal connented to some
> > > chardev.
> > > In the libvirt setting, it will allow to implement a resizable
> > > terminal
> > > for virsh console and other libvirt clients.
> > > 
> > > This patch series was originally authored by Szymon Lukasz and
> > > submitted
> > > to qemu-devel about 5 years ago. The previous submission can be
> > > found at
> > > <
> > > https://lists.nongnu.org/archive/html/qemu-devel/2020-06/msg09591.
> > > html>.
> > > I have updated the patches to be compatible with latest master
> > > and made
> > > a few small changes of my own, including the addition of Windows
> > > support.
> > > 
> > > Probably the most important change I made is the swapping of rows
> > > and
> > > cols fields in resize messages. I would like to hear some
> > > feedback on
> > > this change from reviewers. The problem is that for a long time,
> > > the
> > > Linux kernel used a different field order from what was specified
> > > in the
> > > virtio spec. The kernel implementation was apparently merged
> > > around 2010,
> > > while the virtio spec came in 2014, so when a previous version of
> > > this
> > > patch series was being discussed here on this mailing list in
> > > 2020, it
> > > was decided that QEMU should match the Linux implementation, and
> > > ideally,
> > > the virtio spec should be changed.
> > > 
> > > However, recently, the Linux kernel implementation was changed to
> > > conform
> > > to the spec:
> > > <https://git.kernel.org/linus/5326ab737a47278dbd16ed3ee7380b26c70
> > > 56ddd>.
> > > As a result, to be compatible with latest kernel releases, QEMU
> > > needs to
> > > also use the field order matching the specification. I have
> > > changed the
> > > patch to use the spec-compliant order, so it works correctly with
> > > latest
> > > kernels now.
> > > 
> > 
> > Well this is not in any release yet. If you want me to revert that
> > one, let me know ASAP. Maximilian?
> > 
> > > That leaves the issue of older kernels. There are about 15 years'
> > > worth
> > > of kernel versions with the swapped field order, including the
> > > kernel
> > > currently shipped in Debian stable. The effects of the swapped
> > > dimensions
> > > can sometimes be quite annoying - e.g. if you have a terminal
> > > with
> > > 24 rows, this will be interpreted as 24 columns, and your shell
> > > may limit 
> > > line editing to this small space, most of which will be taken by
> > > your
> > > prompt. The patch series in its current form provides no way to
> > > disable
> > > the console size functionality,
> > 
> > Well I see the console-size property, no?
> 
> At least in the case of libvirt managed VMs, this series does
> nothin by default, as they won't be using the 'stdio' chardev,
> they'll require libvirt to first wire up the new QMP command,
> and then apps using libvirt to call it. So in that sense, it'll
> take a while before the effects are seen by users.

Correct me if I'm wrong on this, but shouldn't the 'pty' chardev also
be able to take advantage of the same size change mechanisms as the
'stdio' chardev (receiving SIGWINCH and being able to use the ioctl
TIOCGWINSZ)? If so the work for the 'stdio' chardev should probably be
replicated for the 'pty' chardev. 

> 
> > > so users may end up worse off than if
> > > the functionality were not implemented at all.
> > 
> > If we want to keep the Linux patch, the straight forward way is to
> > send
> > the fix to stable@ then poke at Debian at al to fix their kernels.
> > 
> > Another option is to make the property default to off, have
> > management turn it on when guest is up to date.
> > 
> > But it really sounds like we should revert that Linux patch.
> > I posted a revert, pls comment.
> 
> What about other non-Linux guest OS that may have correctly
> implemented the virtio spec ?
> 
> At least FreeBSD appears to /not/ implemenmt resize at all:
> 
>  
> https://github.com/freebsd/freebsd-src/blob/main/sys/dev/virtio/console/virtio_console.c#L884
> 
> Do we have a Windows impl of virtio-console with resize support ?
> 
> Any other places we should check ?
> 
> With regards,
> Daniel

Re: [PATCH v4 00/10] virtio-console: notify about the terminal size

Posted by Daniel P. Berrangé 1 week, 6 days ago

On Mon, Sep 15, 2025 at 10:41:44AM +0200, Maximilian Immanuel Brandtner wrote:
> On Fri, 2025-09-12 at 09:50 +0100, Daniel P. Berrangé wrote:
> > On Fri, Sep 12, 2025 at 04:41:02AM -0400, Michael S. Tsirkin wrote:
> > > On Fri, Sep 12, 2025 at 05:39:45AM +0200, Filip Hejsek wrote:
> > > > The goal of this series is to have a resizable terminal into a
> > > > guest
> > > > without having to set up networking and using, e.g. ssh.
> > > > 
> > > > The virtio spec allows a virtio-console device to notify the
> > > > guest about
> > > > terminal resizes in the host. Linux Kernel implements the driver
> > > > part of
> > > > the spec. This series implement the device part in QEMU.
> > > > 
> > > > This series adds support for a resizable terminal if a virtio
> > > > console
> > > > device is connected to the stdio backend.
> > > > 
> > > > This series also introduces resize messages that can be sent over
> > > > QMP to
> > > > notify QEMU about the size of the terminal connented to some
> > > > chardev.
> > > > In the libvirt setting, it will allow to implement a resizable
> > > > terminal
> > > > for virsh console and other libvirt clients.
> > > > 
> > > > This patch series was originally authored by Szymon Lukasz and
> > > > submitted
> > > > to qemu-devel about 5 years ago. The previous submission can be
> > > > found at
> > > > <
> > > > https://lists.nongnu.org/archive/html/qemu-devel/2020-06/msg09591.
> > > > html>.
> > > > I have updated the patches to be compatible with latest master
> > > > and made
> > > > a few small changes of my own, including the addition of Windows
> > > > support.
> > > > 
> > > > Probably the most important change I made is the swapping of rows
> > > > and
> > > > cols fields in resize messages. I would like to hear some
> > > > feedback on
> > > > this change from reviewers. The problem is that for a long time,
> > > > the
> > > > Linux kernel used a different field order from what was specified
> > > > in the
> > > > virtio spec. The kernel implementation was apparently merged
> > > > around 2010,
> > > > while the virtio spec came in 2014, so when a previous version of
> > > > this
> > > > patch series was being discussed here on this mailing list in
> > > > 2020, it
> > > > was decided that QEMU should match the Linux implementation, and
> > > > ideally,
> > > > the virtio spec should be changed.
> > > > 
> > > > However, recently, the Linux kernel implementation was changed to
> > > > conform
> > > > to the spec:
> > > > <https://git.kernel.org/linus/5326ab737a47278dbd16ed3ee7380b26c70
> > > > 56ddd>.
> > > > As a result, to be compatible with latest kernel releases, QEMU
> > > > needs to
> > > > also use the field order matching the specification. I have
> > > > changed the
> > > > patch to use the spec-compliant order, so it works correctly with
> > > > latest
> > > > kernels now.
> > > > 
> > > 
> > > Well this is not in any release yet. If you want me to revert that
> > > one, let me know ASAP. Maximilian?
> > > 
> > > > That leaves the issue of older kernels. There are about 15 years'
> > > > worth
> > > > of kernel versions with the swapped field order, including the
> > > > kernel
> > > > currently shipped in Debian stable. The effects of the swapped
> > > > dimensions
> > > > can sometimes be quite annoying - e.g. if you have a terminal
> > > > with
> > > > 24 rows, this will be interpreted as 24 columns, and your shell
> > > > may limit 
> > > > line editing to this small space, most of which will be taken by
> > > > your
> > > > prompt. The patch series in its current form provides no way to
> > > > disable
> > > > the console size functionality,
> > > 
> > > Well I see the console-size property, no?
> > 
> > At least in the case of libvirt managed VMs, this series does
> > nothin by default, as they won't be using the 'stdio' chardev,
> > they'll require libvirt to first wire up the new QMP command,
> > and then apps using libvirt to call it. So in that sense, it'll
> > take a while before the effects are seen by users.
> 
> Correct me if I'm wrong on this, but shouldn't the 'pty' chardev also
> be able to take advantage of the same size change mechanisms as the
> 'stdio' chardev (receiving SIGWINCH and being able to use the ioctl
> TIOCGWINSZ)? If so the work for the 'stdio' chardev should probably be
> replicated for the 'pty' chardev.

Yes, if using a suitable client app, it ought to work for
'pty' I think.


With regards,
Daniel
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[PATCH] char-pty: add support for the terminal size

Posted by Maximilian Immanuel Brandtner 1 week, 6 days ago

Update the terminal size upon SIGWINCH delivery.

To be committed with the patch-set: [PATCH v4 00/10] virtio-console: notify about the terminal size

Signed-off-by: Maximilian Immanuel Brandtner <maxbr@linux.ibm.com>
---
 chardev/char-pty.c | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/chardev/char-pty.c b/chardev/char-pty.c
index 674e9b3f14..802bae9037 100644
--- a/chardev/char-pty.c
+++ b/chardev/char-pty.c
@@ -28,6 +28,7 @@
 #include "io/channel-file.h"
 #include "qemu/sockets.h"
 #include "qemu/error-report.h"
+#include "qemu/main-loop.h"
 #include "qemu/module.h"
 #include "qemu/option.h"
 #include "qemu/qemu-print.h"
@@ -35,6 +36,8 @@
 #include "chardev/char-io.h"
 #include "qom/object.h"
 
+#include <sys/ioctl.h>
+
 struct PtyChardev {
     Chardev parent;
     QIOChannel *ioc;
@@ -43,6 +46,8 @@ struct PtyChardev {
     int connected;
     GSource *timer_src;
     char *path;
+
+    Notifier resize_notifier;
 };
 typedef struct PtyChardev PtyChardev;
 
@@ -85,6 +90,15 @@ static void pty_chr_rearm_timer(Chardev *chr, int ms)
     g_free(name);
 }
 
+static void pty_chr_resize(PtyChardev *s)
+{
+    struct winsize ws;
+
+    if (ioctl(QIO_CHANNEL_FILE(s->ioc)->fd, TIOCGWINSZ, &ws) != -1) {
+        qemu_chr_resize(CHARDEV(s), ws.ws_col, ws.ws_row);
+    }
+}
+
 static void pty_chr_update_read_handler(Chardev *chr)
 {
     PtyChardev *s = PTY_CHARDEV(chr);
@@ -331,6 +345,12 @@ static int qemu_openpty_raw(int *aslave, char *pty_name)
     return amaster;
 }
 
+static void term_resize_notify(Notifier *n, void *data)
+{
+    PtyChardev *s = container_of(n, PtyChardev, resize_notifier);
+    pty_chr_resize(s);
+}
+
 static void char_pty_open(Chardev *chr,
                           ChardevBackend *backend,
                           bool *be_opened,
@@ -376,6 +396,10 @@ static void char_pty_open(Chardev *chr,
             s->path = g_strdup(path);
         }
     }
+
+    pty_chr_resize(s);
+    s->resize_notifier.notify = term_resize_notify;
+    sigwinch_add_notifier(&s->resize_notifier);
 }
 
 static void char_pty_parse(QemuOpts *opts, ChardevBackend *backend,
-- 
2.50.1

[PATCH v2] char-pty: add support for the terminal size

Posted by Maximilian Immanuel Brandtner 1 week, 5 days ago

Update the terminal size upon SIGWINCH delivery.

Signed-off-by: Maximilian Immanuel Brandtner <maxbr@linux.ibm.com>
---

To be committed with the patch-set: [PATCH v4 00/10] virtio-console: notify about the terminal size

v1 -> v2: Move comment regarding patch dependencies to note section
---
 chardev/char-pty.c | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/chardev/char-pty.c b/chardev/char-pty.c
index 674e9b3f14..802bae9037 100644
--- a/chardev/char-pty.c
+++ b/chardev/char-pty.c
@@ -28,6 +28,7 @@
 #include "io/channel-file.h"
 #include "qemu/sockets.h"
 #include "qemu/error-report.h"
+#include "qemu/main-loop.h"
 #include "qemu/module.h"
 #include "qemu/option.h"
 #include "qemu/qemu-print.h"
@@ -35,6 +36,8 @@
 #include "chardev/char-io.h"
 #include "qom/object.h"
 
+#include <sys/ioctl.h>
+
 struct PtyChardev {
     Chardev parent;
     QIOChannel *ioc;
@@ -43,6 +46,8 @@ struct PtyChardev {
     int connected;
     GSource *timer_src;
     char *path;
+
+    Notifier resize_notifier;
 };
 typedef struct PtyChardev PtyChardev;
 
@@ -85,6 +90,15 @@ static void pty_chr_rearm_timer(Chardev *chr, int ms)
     g_free(name);
 }
 
+static void pty_chr_resize(PtyChardev *s)
+{
+    struct winsize ws;
+
+    if (ioctl(QIO_CHANNEL_FILE(s->ioc)->fd, TIOCGWINSZ, &ws) != -1) {
+        qemu_chr_resize(CHARDEV(s), ws.ws_col, ws.ws_row);
+    }
+}
+
 static void pty_chr_update_read_handler(Chardev *chr)
 {
     PtyChardev *s = PTY_CHARDEV(chr);
@@ -331,6 +345,12 @@ static int qemu_openpty_raw(int *aslave, char *pty_name)
     return amaster;
 }
 
+static void term_resize_notify(Notifier *n, void *data)
+{
+    PtyChardev *s = container_of(n, PtyChardev, resize_notifier);
+    pty_chr_resize(s);
+}
+
 static void char_pty_open(Chardev *chr,
                           ChardevBackend *backend,
                           bool *be_opened,
@@ -376,6 +396,10 @@ static void char_pty_open(Chardev *chr,
             s->path = g_strdup(path);
         }
     }
+
+    pty_chr_resize(s);
+    s->resize_notifier.notify = term_resize_notify;
+    sigwinch_add_notifier(&s->resize_notifier);
 }
 
 static void char_pty_parse(QemuOpts *opts, ChardevBackend *backend,
-- 
2.50.1