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 24F55CAC59F for ; Thu, 18 Sep 2025 08:49:06 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1uzAJg-0003zd-BB; Thu, 18 Sep 2025 04:48:36 -0400 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 1uzAJe-0003z6-4c for qemu-devel@nongnu.org; Thu, 18 Sep 2025 04:48:34 -0400 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 1uzAJZ-0003PU-Vn for qemu-devel@nongnu.org; Thu, 18 Sep 2025 04:48:33 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1758185305; 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=3C0wxY+SOI8SbQ4JoLJErdE83oPuLxa/s9oZU6QBom0=; b=S+M6maHM8n8sOwTl964VJUSXlj1FJ3qW9f4ss8aeIMzE3dFuH/n00xiyNSIj6yPZ+ZmcjW bXsunQa3GaWm2ysDoY+NhyHTT4smHRDh6hY3jbDtPp1veH0tp1rQ+0ij6urzpztwO2G2Hq IEdwhk0k1h3EfSsYhymOd5RuN1NkdUo= Received: from mx-prod-mc-02.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-599--Br-DY42PP-iDwaYnTHUYQ-1; Thu, 18 Sep 2025 04:48:22 -0400 X-MC-Unique: -Br-DY42PP-iDwaYnTHUYQ-1 X-Mimecast-MFC-AGG-ID: -Br-DY42PP-iDwaYnTHUYQ_1758185300 Received: from mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.17]) (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-02.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 82EB41956086; Thu, 18 Sep 2025 08:48:20 +0000 (UTC) Received: from redhat.com (unknown [10.42.28.161]) by mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 861071955F21; Thu, 18 Sep 2025 08:48:13 +0000 (UTC) Date: Thu, 18 Sep 2025 09:48:09 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Maximilian Immanuel Brandtner Cc: Filip Hejsek , amit@kernel.org, armbru@redhat.com, eblake@redhat.com, eduardo@habkost.net, lvivier@redhat.com, marcandre.lureau@redhat.com, marcel.apfelbaum@gmail.com, mst@redhat.com, noh4hss@gmail.com, pbonzini@redhat.com, philmd@linaro.org, qemu-devel@nongnu.org, wangyanan55@huawei.com, zhao1.liu@intel.com, nsg@linux.ibm.com Subject: Re: [PATCH v2] char-pty: add support for the terminal size Message-ID: References: <95142e7fd2a103cfb8d8bea9727117bfe952baec.camel@linux.ibm.com> <0A6C8C3D-68E7-4E88-BEBE-D653135915DF@gmail.com> <15cc6bcd675f2e20efe4fbd6332018a693122b9c.camel@gmail.com> <8979fb7f27b9dbe48f6419d515c4d33a77cefe0a.camel@linux.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <8979fb7f27b9dbe48f6419d515c4d33a77cefe0a.camel@linux.ibm.com> User-Agent: Mutt/2.2.14 (2025-02-20) X-Scanned-By: MIMEDefang 3.0 on 10.30.177.17 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=-0.001, 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: , 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 Thu, Sep 18, 2025 at 10:39:28AM +0200, Maximilian Immanuel Brandtner wrote: > On Thu, 2025-09-18 at 09:35 +0100, Daniel P. Berrangé wrote: > > On Wed, Sep 17, 2025 at 08:29:39PM +0200, Filip Hejsek wrote: > > > On Wed, 2025-09-17 at 18:53 +0100, Daniel P. Berrangé wrote: > > > > On Wed, Sep 17, 2025 at 07:11:03PM +0200, Filip Hejsek wrote: > > > > > On Wed, 2025-09-17 at 17:17 +0100, Daniel P. Berrangé wrote: > > > > > > > > > > > We shouldn't send any size info to the guest if the hsot > > > > > > backend > > > > > > does not have it available. > > > > > > > > > > Does that mean sending 0x0, or not sending anything at all? The > > > > > later > > > > > is tricky, because for non-multiport devices it's only really > > > > > possible > > > > > by not offering the feature bit, but we don't know upfront > > > > > whether the > > > > > size command will be used. > > > > What are the semantics in the guest if we sent 0x0 as the size ? > > AFAICT the virtio spec is silent on what '0x0' means. > > > > It seems like it could conceivably have any behaviour, whether > > a zero-size console, or a console clamped to 1x1 as a min size, > > or a console reset to an arbitrary guest default like 80x24. > > During testing the kernel resized the tty to 0x0 if VirtIO instructed > the kernel to resize the tty to 0x0. If the chardev backends are defaulting to 0x0 for everything except the 'stdio' backend, then this series is surely going to break all existing usage of virtio-console for non-stdio backends ? What am I missing here ? 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 :|