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[80.230.35.22]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-4356997e6dasm22042594f8f.32.2026.01.19.01.43.22 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 19 Jan 2026 01:43:24 -0800 (PST) Date: Mon, 19 Jan 2026 04:43:21 -0500 From: "Michael S. Tsirkin" To: Daniel =?iso-8859-1?Q?P=2E_Berrang=E9?= Cc: Filip Hejsek , 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 , Maximilian Immanuel Brandtner , Szymon Lukasz Subject: Re: [PATCH v6 08/12] virtio-serial-bus: add terminal resize messages Message-ID: <20260119044148-mutt-send-email-mst@kernel.org> References: <20260119-console-resize-v6-0-33a7b0330a7a@gmail.com> <20260119-console-resize-v6-8-33a7b0330a7a@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Received-SPF: pass client-ip=170.10.129.124; envelope-from=mst@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -21 X-Spam_score: -2.2 X-Spam_bar: -- X-Spam_report: (-2.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.077, 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_H2=-0.01, 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: qemu development 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 Mon, Jan 19, 2026 at 09:38:41AM +0000, Daniel P. Berrangé wrote: > On Mon, Jan 19, 2026 at 04:27:51AM +0100, Filip Hejsek wrote: > > Implement the part of the virtio spec that allows to notify the virtio > > driver about terminal resizes. The virtio spec contains two methods to > > achieve that: > > > > For legacy drivers, we have only one port and we put the terminal size > > in the config space and inject the config changed interrupt. > > > > For multiport devices, we use the control virtqueue to send a packet > > containing the terminal size. Note that old versions of the Linux kernel > > used an incorrect order for the fields (rows then cols instead of cols > > then rows), until it was fixed by commit 5326ab737a47278dbd16ed3ee7380b26c7056ddd. > > > > As a result, when using a Linux kernel older than 6.15, the number of rows > > and columns will be swapped. > > > > Based on a patch originally written by Szymon Lukasz , > > but partially rewritten to fix various corner cases. > > > > Signed-off-by: Szymon Lukasz > > Signed-off-by: Filip Hejsek > > --- > > hw/char/trace-events | 1 + > > hw/char/virtio-serial-bus.c | 76 +++++++++++++++++++++++++++++++++++++-- > > hw/core/machine.c | 4 ++- > > include/hw/virtio/virtio-serial.h | 5 +++ > > 4 files changed, 83 insertions(+), 3 deletions(-) > > > > > @@ -1158,6 +1228,8 @@ static const Property virtio_serial_properties[] = { > > 31), > > DEFINE_PROP_BIT64("emergency-write", VirtIOSerial, host_features, > > VIRTIO_CONSOLE_F_EMERG_WRITE, true), > > + DEFINE_PROP_BIT64("console-size", VirtIOSerial, host_features, > > + VIRTIO_CONSOLE_F_SIZE, true), > > }; > > Given the horrible mess with the kernel intentionally changing its > behaviour after 15 years, I don't think we can we set this to be > enabled by default. > > The recent behaviour change is never going to be backported to enough > stable distros that we can rely on the new behaviour, and thanks to > the change we can't rely on the old behaviour either. We're doomed no > matter what ordernig we use. > > Thus, IMHO, this has to stay set to false indefinitely. Not sure. But what we can do is add another flag to detect new kernels. I'll try to think of a good name but suggestions are welcome. > > static void virtio_serial_class_init(ObjectClass *klass, const void *data) > > diff --git a/hw/core/machine.c b/hw/core/machine.c > > index 6411e68856..50554b8900 100644 > > --- a/hw/core/machine.c > > +++ b/hw/core/machine.c > > @@ -38,7 +38,9 @@ > > #include "hw/acpi/generic_event_device.h" > > #include "qemu/audio.h" > > > > -GlobalProperty hw_compat_10_2[] = {}; > > +GlobalProperty hw_compat_10_2[] = { > > + { "virtio-serial-device", "console-size", "off" }, > > +}; > > const size_t hw_compat_10_2_len = G_N_ELEMENTS(hw_compat_10_2); > > > > GlobalProperty hw_compat_10_1[] = { > > 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 :|