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Tsirkin" To: Filip Hejsek Cc: qemu-devel@nongnu.org, =?iso-8859-1?Q?Marc-Andr=E9?= Lureau , Paolo Bonzini , Laurent Vivier , Amit Shah , Markus Armbruster , Eric Blake , Eduardo Habkost , Marcel Apfelbaum , Philippe =?iso-8859-1?Q?Mathieu-Daud=E9?= , Yanan Wang , Zhao Liu , Szymon Lukasz , Daniel =?iso-8859-1?Q?P=2E_Berrang=E9?= , Maximilian Immanuel Brandtner Subject: Re: [PATCH v4 00/10] virtio-console: notify about the terminal size Message-ID: <20250912044306-mutt-send-email-mst@kernel.org> References: <20250912-console-resize-v4-0-7925e444afc4@gmail.com> <20250912042910-mutt-send-email-mst@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250912042910-mutt-send-email-mst@kernel.org> Received-SPF: pass client-ip=170.10.133.124; envelope-from=mst@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.001, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Fri, Sep 12, 2025 at 04:41:05AM -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 > > . > > 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: . > > 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. Oh no, I was confused. This was in 6.15 and 6.16 :( Pls ignore this, I will reply separately. > > 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