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 DFCBACAC592 for ; Mon, 22 Sep 2025 14:39:12 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1v0hgq-0006ue-7Y; Mon, 22 Sep 2025 10:38:52 -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 1v0hgo-0006th-4e for qemu-devel@nongnu.org; Mon, 22 Sep 2025 10:38:50 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1v0hgh-0000vN-3s for qemu-devel@nongnu.org; Mon, 22 Sep 2025 10:38:49 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1758551922; 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=ErNFbSp4LjMeauYJPbczPvbCQlNXwugfMLcHgK8l9MY=; b=MqUWOUIfwyQKMIUak3iRPOEsYn9qXIdVTmUuBZJytKT3bi/vz33uxKYr/4Jw+f7EL8dG+k qJftxYHX3DG9ZfvCfccivrwnjPqRCE+ko8im0zYBqM++eQpspp6agtvoI0zN+IiEOWWzLP 94dp4ppgTbb9zNvITYzSAOTVPeLLqSY= Received: from mx-prod-mc-04.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-624-n2W0pUO-M4Wl5pHfuME8JA-1; Mon, 22 Sep 2025 10:38:32 -0400 X-MC-Unique: n2W0pUO-M4Wl5pHfuME8JA-1 X-Mimecast-MFC-AGG-ID: n2W0pUO-M4Wl5pHfuME8JA_1758551911 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-04.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 4CD9719560B8; Mon, 22 Sep 2025 14:38:31 +0000 (UTC) Received: from redhat.com (unknown [10.42.28.69]) by mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 84DFD1956056; Mon, 22 Sep 2025 14:38:28 +0000 (UTC) Date: Mon, 22 Sep 2025 15:38:24 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Christian Speich Cc: "Michael S. Tsirkin" , qemu-devel@nongnu.org, Stefano Garzarella , Alex =?utf-8?Q?Benn=C3=A9e?= Subject: Re: [PATCH] virtio: vhost-user-device: Make user creatable again Message-ID: References: <20250919-vhost-user-device-creatable-v1-1-87eefeea7f68@avm.de> <20250919160526-mutt-send-email-mst@kernel.org> 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 3.0 on 10.30.177.17 Received-SPF: pass client-ip=170.10.133.124; envelope-from=berrange@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -24 X-Spam_score: -2.5 X-Spam_bar: -- X-Spam_report: (-2.5 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.442, 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_VALIDITY_CERTIFIED_BLOCKED=0.001, RCVD_IN_VALIDITY_RPBL_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 Mon, Sep 22, 2025 at 03:33:59PM +0200, Christian Speich wrote: > On Mon, Sep 22, 2025 at 12:33:26PM +0100, Daniel P. Berrangé wrote: > > On Fri, Sep 19, 2025 at 04:07:19PM -0400, Michael S. Tsirkin wrote: > > > On Fri, Sep 19, 2025 at 04:30:53PM +0200, Christian Speich wrote: > > > > This removes the change introduced in [1] that prevents the use of > > > > vhost-user-device and vhost-user-device-pci on unpatched QEMU builds. > > > > > > > > [1]: 6275989647efb708f126eb4f880e593792301ed4 > > > > > > > > Signed-off-by: Christian Speich > > > > --- > > > > vhost-user-device and vhost-user-device-pci started out as user > > > > creatable devices. This was changed in [1] when the vhost-user-base was > > > > introduced. > > > > > > > > The reason given is to prevent user confusion. Searching qemu-discuss or > > > > google for "vhost-user-device" I've seen no confused users. > > > > > > > > Our use case is to provide wifi emulation using "vhost-user-device-pci", > > > > which currently is working fine with the QEMU 9.0.2 present in Ubuntu > > > > 24.04. With newer QEMU versions we now need to patch, distribute and > > > > maintain our own QEMU packages, which is non-trivial. > > > > > > > > So I want to propose lifting this restriction to make this feature > > > > usable without a custom QEMU. > > > > > > > > [1]: 6275989647efb708f126eb4f880e593792301ed4 > > > > > > The confusion is after someone reuses the ID you are claiming without > > > telling anyone and then linux guests will start binding that driver to > > > your device. > > > > > > > > > We want people doing this kind of thing to *at a minimum* > > > go ahead and register a device id with the virtio TC, > > > but really to write and publish a spec. > > > > Wanting people to register a device ID is a social problem and > > we're trying to apply a technical hammer to it, which is rarely > > an productive approach. > > > > If we want to demonstrate that vhost-user-device is "risky", then > > how about we rename it to have an 'x-' prefix and thus disclaim > > any support for it, but none the less allow its use. Document it > > as an experimental device, and if it breaks, users get to keep > > both pieces. > > I don't mind the 'x-'. And if that makes it clear, that this is used > without any warrenty, sure! > > However I'm not sure where the "risky" comes from. Initially confusion > was given as reason. I view it as "risky" in two ways - this device makes it very easy for a user to shoot themselves in the foot - we dont want to have to think about compatibility across QEMU releases in case there is something peculiar about a particular device type. IMHO, adding the 'x-' prefix and disclaiming full support is sufficient mitigation. > Initially I thought about some kind of '--i-really-want-to-do-this' > flag, but somehow I don't really see this device to bethis harmful > to to warrent that big of a deterrent. I agree. 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 :|