From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 46C1ED2ED0F for ; Tue, 20 Jan 2026 10:11:11 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1vi8gv-0000TH-B3; Tue, 20 Jan 2026 05:10:29 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1vi8gt-0000Sd-1h for qemu-devel@nongnu.org; Tue, 20 Jan 2026 05:10:27 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1vi8gq-0003o9-8e for qemu-devel@nongnu.org; Tue, 20 Jan 2026 05:10:26 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1768903821; h=from:from:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=bFH5OSnxS7QuXQalBgVv301Uy5NeL9OShjIbTqEsiKg=; b=Bcxycnm80qczybTxaSlM55VpDhhwcE2dG17i31d5pGXa9iS+7BLqSOWTxNLBYGppcD+Av3 +HJq/CwH0zb+wBVIqpp6CrhaXlgjVwXo+E3sNmDvXlcPVBs9nm5ahRw/NZBuSTIDeo+aSl 0SzLaBOxc//401WIcrN+WsG7+nhV688= Received: from mx-prod-mc-08.mail-002.prod.us-west-2.aws.redhat.com (ec2-35-165-154-97.us-west-2.compute.amazonaws.com [35.165.154.97]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-549-Ies4DbEKOAOfMnQuWpSs8w-1; Tue, 20 Jan 2026 05:10:17 -0500 X-MC-Unique: Ies4DbEKOAOfMnQuWpSs8w-1 X-Mimecast-MFC-AGG-ID: Ies4DbEKOAOfMnQuWpSs8w_1768903816 Received: from mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.93]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id DF1541800357; Tue, 20 Jan 2026 10:10:15 +0000 (UTC) Received: from redhat.com (unknown [10.42.28.89]) by mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 0F99A1800993; Tue, 20 Jan 2026 10:10:07 +0000 (UTC) Date: Tue, 20 Jan 2026 10:10:04 +0000 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Filip Hejsek Cc: qemu-devel@nongnu.org, =?utf-8?Q?Marc-Andr=C3=A9?= Lureau , Paolo Bonzini , "Michael S. Tsirkin" , Laurent Vivier , Amit Shah , Markus Armbruster , Eric Blake , Eduardo Habkost , Marcel Apfelbaum , Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= , Yanan Wang , Zhao Liu , Maximilian Immanuel Brandtner , Szymon Lukasz Subject: Re: [PATCH v6 08/12] virtio-serial-bus: add terminal resize messages Message-ID: References: <20260119-console-resize-v6-0-33a7b0330a7a@gmail.com> <20260119-console-resize-v6-8-33a7b0330a7a@gmail.com> <6910accb5917c60e89801af1c3528187e732166f.camel@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/2.2.14 (2025-02-20) X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.93 Received-SPF: pass client-ip=170.10.129.124; envelope-from=berrange@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=-0.016, 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=0.001, 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: qemu development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Tue, Jan 20, 2026 at 11:07:16AM +0100, Filip Hejsek wrote: > On Tue, 2026-01-20 at 09:54 +0000, Daniel P. Berrangé wrote: > > On Tue, Jan 20, 2026 at 10:50:04AM +0100, Filip Hejsek wrote: > > > On Mon, 2026-01-19 at 04:27 +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(-) > > > > > > > > [...] > > > > > > > > diff --git a/include/hw/virtio/virtio-serial.h b/include/hw/virtio/virtio-serial.h > > > > index 60641860bf..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; > > > > }; > > > > > > I found a bug: after a migration, the guest is not informed about the > > > new console size. I see two ways to fix this: either add the cols and > > > rows fields to the migration stream, or always send the console size to > > > the guest after migration, even if it might not have changed. Which do > > > you prefer? Modifying the migration stream is somewhat annoying, > > > because both versions will have to be supported, and also the device > > > still uses legacy save/load functions rather than VMState. > > > > On the backend side, I'd consider migration to be equivalent to closing > > and re-opening the backend character device. That should imply sending > > a resize event on migration completion. I'm surprised the chardev on > > the dst isn't already triggering that when it gets connected, but perhaps > > that is too early & getting lost ? > > The virtio device caches the size and doesn't send a resize message if > the size hasn't actually changed. If the size on the dest has not changed vs the size on the src, that's fine surely ? We only need to tell the guest a new size if the dst was different from the source after migration 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 :|