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 lists1p.gnu.org (lists1p.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 B2D55C43458 for ; Thu, 9 Jul 2026 15:59:30 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists1p.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1whr9X-0004PK-O2; Thu, 09 Jul 2026 11:59:07 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists1p.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1whr9W-0004OZ-6f for qemu-arm@nongnu.org; Thu, 09 Jul 2026 11:59:06 -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 1whr9U-0002nS-Bp for qemu-arm@nongnu.org; Thu, 09 Jul 2026 11:59:05 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1783612743; 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=YWF/eRUKuEvtmDKG/UlPZ8rYUVXNLbdBgzDg7U2hqMs=; b=D2MOIA/a1iHlxZx627ftesHPIBguBCOkmlJawbaN/KyjA0nUGWtWmAG7iW5+7hcpGIJEJz k1UiLWuDxub9RbXcA5Eb2pTjooKSdMtG2YqIYDmVRIis6RAVxj0KRSPMVKPxo7Kqgr97nT PqDO0TMshIeq0asefXL2tny2+ELl0y8= Received: from mx-prod-mc-01.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-465-dHq7FrBTMlO_XqXO2DRLZQ-1; Thu, 09 Jul 2026 11:58:59 -0400 X-MC-Unique: dHq7FrBTMlO_XqXO2DRLZQ-1 X-Mimecast-MFC-AGG-ID: dHq7FrBTMlO_XqXO2DRLZQ_1783612738 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-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id AA0D519560BA; Thu, 9 Jul 2026 15:58:56 +0000 (UTC) Received: from redhat.com (unknown [10.44.49.59]) by mx-prod-int-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 22FDD1955DC9; Thu, 9 Jul 2026 15:58:51 +0000 (UTC) Date: Thu, 9 Jul 2026 16:58:48 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: =?utf-8?Q?Marc-Andr=C3=A9?= Lureau Cc: Peter Maydell , Markus Armbruster , qemu-devel@nongnu.org, Jan Kiszka , qemu-arm@nongnu.org, BALATON Zoltan , qemu-ppc@nongnu.org, Huacai Chen , Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= , Jiaxun Yang , Gerd Hoffmann Subject: Re: A few Machines crash when "no default audio driver available" Message-ID: References: <87o6gge6b0.fsf@pond.sub.org> <87zf00cn7m.fsf@pond.sub.org> MIME-Version: 1.0 In-Reply-To: User-Agent: Mutt/2.3.2 (2026-04-26) X-Scanned-By: MIMEDefang 3.0 on 10.30.177.17 X-Mimecast-MFC-PROC-ID: 5OGdMI1zwMr-K2wYsI4CIIc5euoW2ek8ky8FzmBmahs_1783612738 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit 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: 8 X-Spam_score: 0.8 X-Spam_bar: / X-Spam_report: (0.8 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.445, 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_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_SBL_CSS=3.335, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=no autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-arm@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-arm-bounces+qemu-arm=archiver.kernel.org@nongnu.org Sender: qemu-arm-bounces+qemu-arm=archiver.kernel.org@nongnu.org On Thu, Jul 09, 2026 at 07:31:31PM +0400, Marc-André Lureau wrote: > Hi > > On Thu, Jul 9, 2026 at 6:02 PM Daniel P. Berrangé wrote: > > > > On Thu, Jul 09, 2026 at 05:54:30PM +0400, Marc-André Lureau wrote: > > > Hi > > > > > > On Thu, Jul 9, 2026 at 5:44 PM Peter Maydell wrote: > > > > > > > > On Thu, 9 Jul 2026 at 14:32, Daniel P. Berrangé wrote: > > > > > > > > > > On Thu, Jul 09, 2026 at 03:22:05PM +0200, Markus Armbruster wrote: > > > > > > Cc: mainainters for "Overall Audio backends" > > > > > > Peter Maydell writes: > > > > > > > > > > > > > On Thu, 9 Jul 2026 at 12:44, Markus Armbruster wrote: > > > > > > >> > > > > > > >> I stumbled over ARM machine musicpal, PPC machines pegasos1, pegasos2, > > > > > > >> and MIPS machine fuloong2e crashes. > > > > > > >> > > > > > > >> I run them like this: > > > > > > >> > > > > > > >> $ qemu-system-aarch64 -M musicpal -nodefaults -S -display none -monitor stdio > > > > > > > > > > > > > >> Died when device_set_realized() tried to propagate a "no default audio > > > > > > >> driver available" error to &error_abort. > > > > > > > > > > > > > > Is this something we want to have be a possibility the devices > > > > > > > have to cope with? Can we have the "ignores all audio data" > > > > > > > backend be always available instead? > > > > > > > > > > > > There's plenty of precedence for /dev/null-like backends. > > > > > > > > > > > > > Otherwise every audio device needs to cope with "there is no > > > > > > > audio backend available" and implement "do nothing with the > > > > > > > audio data" itself. > > > > > > > > > > > > Yes. > > > > > > > > > > We've got a bit of tension between "no defaults" and "builtin audio > > > > > devices" here. > > > > > > > > > > Cnosider if I had instead done > > > > > > > > > > qemu-system-x86_64 -M pc -device ac97 -nodefaults > > > > > > > > > > It is not unreasonable to expect to see an error because you asked > > > > > explicitly for 'ac97' and forgot to wire up the required audio > > > > > backend, and asked to NOT have any defaults. > > > > > > > > > > But with your 'musicpal' machine example, you never asked for the > > > > > frontend device, so you should be forgiven for also not asking > > > > > for a audio backend. > > > > > > > > Ah, so this is because of -nodefaults, not because QEMU was > > > > somehow built with no audio backends in it. > > > > > > > > > If we guarantee a /dev/null audio backend always exists, we help > > > > > the second case but degrade the first case > > > > > > > > As a possible analogy, for network devices we just warn in > > > > the analogous "device created but no backend wired up": > > > > > > > > ./build/x86/qemu-system-x86_64 -nodefaults -device e1000 -display none > > > > qemu-system-x86_64: warning: nic e1000.0 has no peer > > > > > > > > and the effective behaviour is that output packets are dropped. > > > > > > > > We could make audio devices do that (which would be basically > > > > equivalent to "if we need an audio backend and we don't have > > > > one, warn and create the null backend"). > > > > > > > > > > Note that we don't have a real "null" backend. The "none" backend does > > > mixing/resampling/volume before dropping the audio (its parent is > > > MIXENG_BACKEND). I think it would be worth to add (so one day we can > > > compile qemu without the whole audio/ engine) > > > > Rather than adding "null" backend, IMHO, we should make "none" do > > what its name suggests, by removing the MIGENG_BACKEND from it. > > > > It's a bit more complicated, the "none" backend can be used by vnc > (not spice or dbus), and we have the now-deprecated HMP wavcapture > command. Oh right because VNC used the capture APIs to receive the audio. It should probably have had an explicit "vnc" audio backend like spice did :-( > > Note, the new "qemu-vnc" server does not mix/resample audio at this > point, it takes the first audio stream instead. > > Fwiw, a "null" audio backend would still need to process audio data at > a correct pace. > With regards, Daniel -- |: https://berrange.com ~~ https://hachyderm.io/@berrange :| |: https://libvirt.org ~~ https://entangle-photo.org :| |: https://pixelfed.art/berrange ~~ https://fstop138.berrange.com :|